Retired Engineer, machinist and shop teacher with over 50 years experience. The best advice is use the tool manufacturer's recommended speeds and feeds. Watching the second piece, you're still not feeding fast enough. watch the short chips in the first cuts, they roll up and break, that will happen at any diameter IF you use the best feed rate. You don't need the oil brush, it doesn't work, make a drip bottle if you must use lube, but water based coolant is better, it actually cools the tool and part.
Part of the issue in my experience is don't use a brush. That only gets oil to the outside surfaces on a deep parting operation. Centrifugal force slings the oil back out with very little getting to the point of cut. I typically use a squeeze bottle to drip oil at the back side of the cut and let it carry through keeping it wet. I also suspect with a VFD spindle drive at low RPM, there really isn't much torque available if you look at the torque curve for that motor.
Yep. Small squirty bottle with a needle on it. And soluble oil rather than traditional cutting oil - the heat from a cut like this will make so much smoke that you can't see the lathe, whereas soluble oil will make mostly steam.
McMaster has bottles like this that accepts lure lock needles. They also sell variety pack of needles so you can experiment and get just the right needle ID for dispensing the fluid
I've never used a small lathe, but in my CNC world I have learned to never hone carbide inserts and to make sure they have an appropriate load. Early days when I first used carbide drills, the tool rep laughed at how slow I was going.....chewing up carbide tools. I quadrupled the feed rate and the tool lasted 10x longer. What an eye popping lesson.
Yes, often misunderstood about carbide inserts, they must be pushed to create enough heat at the cutting area to function. Less than that, chipping or burning of the carbide insert is assured. This is also why altering the carbide insert in an attempt to gain a "edge" is not wise and counterproductive in every way.
Haven't seen the other video but i keep telling my students that if you're getting vibrations or a bad surface finish, don't slow down, increase the spindle speed and go from there. Vibrations are usually caused at a certain frequency, you either have to go down or up to get away from it. Slowing down carbide tools isn't always the best option, carbide wants to get pushed. Since you're not using a geared lathe, you're left with no torque advantage in slower speeds, so you gotta get it where the torque is. Increased speed will also help to overcome stuck chips or a slightly too beefy feed rate for a short moment (when hand feeding) Some said cutting oil and a brush doesn't help and that centrifugal force won't make it cut better, but when parting off, a little bit of oil, is still better than no oil. Another thing i like to do is to use wider parting cutters and inserts, it improves rigidity and therefore keeps the cutting geometry more stable, even on smaller lathes.
@@Clough42 Parting like this with carbide is where "Low Volume" flood coolant comes in handy if your machin is capable of it - A trickle into the cut trough but not enough to spash onto the chuck and become a water park
@@bengrogan9710 A 1,5 liter cola bottle upside down with a nice 3D printed adapter for a hose/pipe with a little valve on it is enough for 'flood' coolant in this type of operation.
People underestimate these lathes all the time. They are far more capable than the usual teeny cuts shown. I learned this style of parting a few years ago. Very rewarding.
This seems like the perfect reason to add Constant Surface Speed to the VFD via the electronic spindle encoder while using the linear scales for radius input. Once you try CSS machining you will immediately see a productivity and quality improvement. In fact that is the primary reason CNC'd parts look so good.
I know nothing about turning, but I was thinking to myself that he needed a third hand to turn up the speed, to keep the surface speed, as th cutting diameter decreases
Before I started out in hobby machining I'd watched a lot of TH-cam and I knew that "carbide likes to be pushed" - so, in my ignorance, I pushed it. And it worked, just as it did for you. I've never had a problem parting with carbide because I'm not afraid to send it. Power feed works well. You also need a chuck that's in good order. Robin Renzetti had a video on trueing chuck jaws, and started out by showing what kind of deflection you can expect in a part under load if the jaws are bellmouthed. That's a recipe for parting problems.
It really does seem counter intuitive, but carbide loves to be loaded up, and you're also enjoying the higher torque from the motor at that speed. Sadly HSS won't tolerate those speeds and loads, and prefers slow and sharp. I truly believe that there's been a conflation between the two along the line that's made it into lore concerning small machines and carbide. Thanks for mythbusting James.
There’s a great book by George Thomas called Model Engineers Workshop Manual. He used to write for the british byweekly Model Engineer. There’s a chapter called “on parting off”. He devoted an entire chapter to it because on the small lathes like the myford, which is what most steam train guys had, it was the most difficult operation to do. Sometimes in a crash one could even break a cross slide or compound casting. He developed the rear inverted toolpost which is sold by Hemingway kits which solves the rigidity problem. He would frequently demonstrate parting off 1” dia mild steel at 300 rpm with hss, just to show it was easily done. The key is to stop if the chips stop curling and you have to make sure the groove doesn’t jam up with curly chips. You need lots of oil too. Btw that’s the best machining book ever. Full of wisdom and awesome tooling projects. Tee Publishing sells it. Btw parting a 5” dia piece will always be a challenge just because you can’t clear the groove.
+1 for rear parting tool post, it gives better chip clearance (they drop out) but I found the Hemmingway design to lack rigidity and reverted to a solid lump with a blade insert as per Jame's footage at 1.29 bolted to it on centre. Also +1 for lots of watery coolant to help the cooling and washout@@climberjb
One thing I would recommend getting is a little needle tip oiler bottle so you can drip oil into the slot as prodigiously as you like as you part. I also use them all the time for drilling or anytime I want cutting oil in a particular spot.
Even running larger manual lathes, it took me a while to get used to carbide. Once you get used to HSS the habits are hard to break. With most carbide you can run screaming speeds and feeds and will get longer tool life. You just have to get past that initial cringe when you start a cut. Great demonstration
The Pulsing in the hand wheel and its relation to the chuck speed when doing the cut is an interesting observation. It would be interesting to do a balance check of the chuck to confirm this hypothesis. If there is in fact an imbalance an attempt to balance the chuck and thereafter do new test cuts would be interesting exercise. This could perhaps be an idea for a future video?
Perfect 👍 Thank you for sharing your experience. Pls try this also: clamp the carriage, put some round material in your drill chuck that reaches in the borehole. So the parted material can not fly around in your workshop.
i dont know much about small lathe´s but on my job (CNC lathe´s) i Part off with 150-250m/min , F=0.1-0.3mm/rev from 1mm blades up to 10mm as far as i know Carbide loves speed and torqe if you go to slow it will chatter or brake early. The last 1-2mm i slow down so the part dosent fly acros the country
Highly recommend full face protection, I've had carbide inserts chip and get flung all over when high speed grooving goes bad. Glad you've found the sweet spot for your lathe.
Parting is such sweet sorrow. Glad you got it worked out. I remember one time I wanted to make a washer and unwittingly picked up a piece of stainless and work hardened it to the limit. It ate my parting tool. Thanks for the video keep on keeping on.
The thing is that when the diameter of the work goes down as you reach the centre, the surface speed and thus the chip size and cutting loads and everything else changes as well. Carbide really is for very high speeds, large chip loads etc. and never stopping, constant flood coolant etc... so it has it's issues when running on manual lathe, since you can't provide all the parameters for it very consistently. It's a great video, you tried it, learned something, you now know more :D
Watching those videos of high speed CNC machines i've always been amazed at how fast they cut. This video you're doing reinforces the concept of going fast. Thanks for sharing.
yup, some tools can be pushed incredibly hard, last week i was testing some new inserts and tweaking a program for production run of thousands of parts per month... what i ended up with were surface speeds at 360m/min for roughing and 400m/min finishing... also these parts are forged into rough shape, so there is only around 1,5-3mm of material to be removed, full depth of cut, and feed rates around 0,35-0,4mm/rev roughing and up to 0,5mm/rev finishing with wiper inserts...
Thanks James. The best way I found to cutoff is mount the cutoff blade upside down and reverse the lathe or mount the cutoff tool on the back side of cross slide if the lathe doesn't have reverse. What happens, even if you push the cutter hard, is the tool lifts up in the Aloris or other type cassette holders (holders are designed to keep the tool from dropping not rising). The extra benefit is the chips exit out the bottom of the part during cutoff operations. I've cut 1-3/4" PH17-4 stainless and O1 tool steel disks with this method without problems. I even use the cross slide advance to cutoff and I use a drip oiler and not a brush. I made a special holder to mount the cutter upside down and I prefer using the "T" tool steel cutoff blades ~1/16" even on large diameter work. They waste less material and they're designed for razor sharp edges. On micro grain carbides I think you can get away with razor sharp edges but not all carbides work well with honing.
I've had the same exact issues and I have a 14 X 44 heavy solid heavy base lathe. I went through my cross slide and tightened everything up and locked down the compound and have not had a chance to try a cut yet but I have some machinist jacks Im going to be making from 4140 and am def going to try this method. _One thing on the reverse blade mounting I might mention; It doesn't cut any better. What it does is, if the tool binds, the blade will lift off the work, and save the blade. When cutting traditionally, and it binds, the blade digs into the work more and then you get the stoppages and damaged blade._ I'm going to be making an iron block reverse cut off but my reason is actually due to production rather than anything else. *Also, Dave Bruneau at MSC is a good resource if you need help with cut off blades. I talked to him about my cut off woes and he directed me to a new blade series by ISCAR and I got it but as I said I haven't used it yet.* D
I like to use water soluble oil with a drip feed when I cut off, especially larger diameters. I part using a steady rest when possible, as my chuck is not what it once was. I will also use a clamp I crafted from an aluminum ring to place force on the chuck jaws. You really get everything out of that hobby lathe that is possible. Nice job!
Yes James, It works and works well, consistently!!!! I theorize that the increased RPMs actually help in the chip evacuation by throwing them further away from the cut immediately after being shaved off, thus not allowing them to remain in the small space closer to the decreased diameter and with that increased room to move outwards from the centrifugal forces they just dont have time to pack up together and increase friction and jam up. There's a load of physics principals that could probably explain it all , but it all comes down to.... if its not broke dont fix it. Just saying !!!! Excellent vid amdsure it has opened a lot of eyes. Keep up the great work. Don
it has more to do with surface speed, since carbide doesnt like low speeds at all, even 100m/min he used is on the lower end of the scale, some inserts i used in the past liked speeds around 120m/min in stainless and slow down to around 70 in the last couple of mm where the part snaps off, speeds around 180-220m/min were also good for steels similar to 1018 with a slow down to around 450rpm for final break off of the part...
My experience is that WD40 in a can +long straw is better than oil. Also 2mm wide insert works better than 3mm (my lathe is 1300 kg~ 3000lbs). Feeding by hand is better than autofeed. The feed has to be such that the WD40 doesnt steam. I set up the rpms as high as possible, but low enought that the centrifugal force doesnt spray WD40 all over the place (which for most applications is 600 rpm). Also when machining the weldable steels they tend to work harden, and there is no clear conclusion under which conditions. This work hardening is the reason why auto feed doesnt work and will break the insert When the steel work hardens it is an art to take this layer off, and then for some time the tool cuts like a charm, and then the surface workhardens again.
Unless I missed something you installed a one horsepower VFD and motor on your lathe. Since the motor is rated for 60 Hz and last I knew your VFD was set to max at 120Hz. Which I would guess means that above 60Hz motor torque would drop off. So between 6Hz and 60Hz the motor torque would be fairly constant. But because horsepower is torque times speed running below 60Hz means your hp would drop off proportionally also. Cutting metal on a molecular level is braking electron bonds similar to melting. If the metal chip can not get away from the cutting tool fast enough then the chip melts, piles up and re-solidify on the cutting tool. Now it will take more force to continue the cut not only because of the larger mass required to cut but also the re-solidified material has tried to weld itself onto the cutting tool. Thus a recommended minimum cutting speed for steel. This also means a minimum horsepower requirement per cutting width. So for larger diameter parts it would be advantageous to increase the reduction reduction ratio between the motor and the spindle to be able to utilize your available horsepower.
Not having a lathe, and living vicariously through you and Quinn -- it looks like carbide just wants more and faster, regardless of how much and how fast you're already going. Yay/nay?
the point thaat is counter intuitive is that Carbide is too hard to be reliably "Sharp" - thus meaning that a HSS too can Shave were Carbide has to "Rip" The tool pressure needs to be high enough that the Carbide doesn't lift the chip and break off to the rip and fall into the hole - leading to guarenteed chatter
@@bengrogan9710 Could it be that it creates a hill like a bulldozer instead of digging in and then slides over the hill and then slams into the surface after riding down the downhill side ? Maybe it also stops cutting and starts sliding and everything gets deflected, building up energy, until the pressure gets high enough to suddenly dig in really deep.
@alexandern8hgeg5e9 1st part you have backward, it's not that the tip rides over it - the chip is formed with enough strength that it levers itself away as it rolls onto the tool: have you ever felt yourself lifted by the arms and felt your legs go forward into the gap? That sort of effect. For the 2nd part, yes that is why carbide needs higher tool pressure to engage to begin with
It’s the old saying “If you’re not cutting your dulling”. And one type of chatter is called “cut rub cut rub”. One old solution to stopping chatter is adjust your “speed and feed”. That doesn’t mean that you always adjust down. It means you adjust it until you get something that works better.
My lesson from Mr Pete was to make certain the blade is at right angles. I use a square or 123 block against the chuck, but Abom indicates his in and that's probably a better practice. Other hard lessons: 1. Cut or don't cut, but do not linger. Either cut aggressively or pull out of the cut. 2. Angled inserts (GTL or GTR) sound like a good way to control where the final nubbin winds up, but in tough parting jobs they eill twist the today out of position. Pinning the tool post so it is physically blocked from rotating is high on my agenda. 3. Flood coolant helps a lot with keeping things under control. 4. Turn your VFD all the way down (mine has a lower limit of 36Hz) and gradually increase the speed as the cut progresses. Aggressive cuts work, even in my tiny little Taig. On my 13x40 lathe, power feed is your friend. One thing i noticed in your first video is that, judging from the chip formation, the blade isn't quite square. The chip should form a watch spring, not a corkscrew,if the tool is perfectly square. Signed: parted 2.5" SS bar and lived to tell the tale.
Since you have a VFD, next time i would suggest what works in our CNC job shop, even higher surface speeds, if you cant squirt coolant right into the cut, ditch the brush, instead try to gradually increase rpm as the parting diameter shrinks to maintain the surface speed, then when you get to the last few mm (4-6mm) slow it down to around 300-500rpm and finish the cut
I went to school to be a machinist. I have years of manual lathe experience. I have had that handle pulsing you described @ 9:32 on multiple lathes from 15 to 20 inch swing gear head lathes. I have a Grizzly G0602 but it is still crated. My experience has been to feed in aggressively at a content speed almost to the point of feeding faster than it's cutting. And don't stop until you're through. But I never ran over about 500 rpm on say 2 in. (50mm) material. Oh and the lathes I ran didn't have any coolent. I just cut it dry. I never used cutting oil much. Yes it is harder on the tools like that but I wasn't paying for them either. On the HSS parting tool you showed. I noticed it was burnt from grinding. You never want to burn your HSS. Quench it often and early.
I might just give this a try ! I have NEVER had a successful parting off (over many many years) - particularly in aluminium - as you say, the bandsaw is your friend 🙂
I have done the same "trip". Started with HSS parting tools and low revs, learned to grind a concave cutting edge to get thinner chips, but always hated parting. Changed to carbide parting and realized that I could raise the revs and parting gets easier and easier. I´m using oil on a brush as long as the cut is shallow and then I use cutting oil in a spray can when the cut gets deeper because the brush simply doesn´t get that deep. I try to add the cutting oil as close to the parting tip as possible because the centrifugal forces will throw the oil out of the cut otherwise. The reason I start with oil on a brush is simply because it is so much cheaper than spray can oil.
Carbide manufacturers/tooling reps have always told me, carbide loves fast and consistent cuts. When it comes to coolant or cutting oils, flood it or run it dry. Their advise worked for me. I played with mist coolant on the lathe years ago and it worked quite well.
I remember first using a manual lathe. It can definitely be intimidating. Bump your spindle speed up a little bit more and keep your feed about the same and I think you’ll see even more improvement.
I've worked at loads of different machine shop's in general people do run speeds way too slow and a lack of understanding about having a rigid set up also doesn't help. Carbide tool love fast speeds and heavy feeds. I once saw a tool company demonstrate ceramic tips. Bloody hell, 2500 rpm cutting like butter curls only blue in colour more amazing workpiece remains cool.... What an eye opener for a young apprentice back in the 1970s my firm was at the cutting edge of technology. This was a 2" hole from solid in a 6" billet of steel..... At that time the tool rep only had 4tips to try.
Thanks for the video!! It was quite an eye opener!!! My uncle worked as a lathe machinist his whole life in the aerospace industry. He always told me that carbide likes speed. However to prevent wear on my lathes bearing, I usually don't run it above 500 rpm...also the chuck spinning at 1000 rpm during a cut it scary...guess I have to give it a shot!
I have that same lathe and did the variable speed conversion from your videos, and I don't have a problem parting. I have had some experiences when my lathe tool was too low and the material kind of jumps over center and hangs up, but when my tool height is right I have no trouble. Happy for ya' though! Forget that hacksaw stuff!
Run a little lathe from our showroom all the time these are about the same numbers I’ve been running for good results for awhile glad you found something that worked 👍
Wow! Like you, my parting experience has been much the same. And the advice I’ve been given is similar - slow and light. I’m going to try this out on my lathe tomorrow morning!! Thanks so much for sharing this tip. I’m amazed!
I have a smaller lathe, and I've done some very high speed turning with carbide tools. It's not quite the tightrope act that a parting tool is, but it still feels terrifying. I wore a full face shield. That said, I've seen someone using the same lathe I've got to turn hardened steel with carbide bits at max speed. That's not one I'll be trying any time soon. In the video I saw, the chips came off like the part was pissing magma.
I was taught to set the parting tool a smidge above the centerline to help avoid grabbing. The tool will spring down a bit under load, so when you set it (without load), just set it above the center. Cutting with the edge of the tool lower than the center of the part pulls the tool into the cut, and the slack on the crosslide will make it easy for the tool to move forward all by itself. If anything, you probably want to be a little higher than center under load
I set it just slightly above center, with the assumption it would flex. I've seen the opposite advice as well, and had some success with it. I think all of the variables interact and there are multiple ways to succeed. I'm just happy to have found one. :)
I tried far higher than usual RPM parting today on my micro-lathe with a HSS blade. Much easier than usual. I’m bemused by this result, but I’ll take it as a win.
This makes me wonder if you could add a constant surface speed function to your electronic lead screw control. If you could set a surface speed on your interface, figure out a way to get the x position from the DRO, calculate the required RPM, and actively adjust the VFD then you could maintain a constant surface speed as you change the X position. My Trak lathe does this and it’s amazing for part offs.
Thank you so much because I have had the same problem that you were having. I watched this last night this morning I went out and tried it, like you eye protection full face mask expecting it to explode. It worked fantastic. Again, thank you
I've been meaning to buy one of these carbide parting tools. This persuades me, thanks. After struggling parting with his tools, this does seem insanely fast, but it makes sense - faster cutting is what the carbide tools will have been made for on cnc's
Youre correct. The growling at the end is the reduced surface speed. Never hone the edge, it's designed that way for a reason. And feed is your friend. Too sharp and too slow is a recipe for chatter. Settin a touch below center helps to.
Well I am surprised. At 500 rpm I thought no, best slow it down a bit. As you increased rpm I cringed and ashumed you were joking. I was really stunned when you started parting at 1000 rpm. I was even more stunned when it worked. Thanks for trying the great anti comfort-zone YT advice & thanks to those knowlegable YT advisors.
I tried speeding up last month. After referencing the speeds and feeds in my handbook, I did some parting with my HSS part off tool and was also pleasantly surprised.
I'm not all that knowledgeable with carbide myself but one factor I've read more than once is that they can't normally be babied with a very light chip load. As you noted the cutting edge is not razor sharp. And honed or not the first part of the top at least would have hand a touch of that edge left. And what I've read is that for the chip to form correctly, self eject and not jam in the cut that the cut has to be a touch on the aggressive side. And this video seems to support that idea. Mind you I do all my parting with a couple of HSS blades. So what do I know....
I do use 'professional' named inserts and blades. And never experienced any problems parting. So seeing this, and others almost being scared of parting is kinda hilarious 😂. But... It also shows that you shouldn't buy cheap parting tools. I do use power feed most the time, and only use coolant in stainless steel. The oil/brush is only making smoke and nothing else. A carbide insert really like being ~1000c° 😅 But as you also mention, pressure is key. You need to push hard. And after a while you can easily hear and see (or feel) if something is wrong.. and you need to slow down a while. It's key the chips to outwards. And that's what the pressure is all about. New chips push the old outwards. Having the blade under, also causes the blade to have a tendency to being pulled inwards. Always 100% in center height 👍 Best regards
James: I had problems with parting for 20 years on my JET 9x20. tried the 4 bolt compound mount but that didn't fix it. It did improve it. My final solution was a disk that replaced the "stand thing" that had the degrees on it. The disk is tall enough to put the compound up at the same height. I clamp it to the four corners as the disk is the full width of the topslide. I engraved the degrees on it and it in turn it is mounted to the bottom of the compound with 4 additional screws plus the original three. I put a pin in the bottom of the disk to function like the original. still have to get the compound gib tight too. Let me know if you need a picture to visualize. John Orr
It made a big difference for me when I stopped being a fanny and used the power crossfeed. Knowing you, Im sure you could fit a stepper motor on the back side of the cross slide and have an els-cs. Then you would be dangerously close to having a cnc lathe lol. Also, couldn't help but notice you not locking carriage. Which leads me to believe you might be crazy...
Im a mechanic and at work we have an old very sloppy and worn lathe, the whole tool holder can easily jump up and down 3mm or more and cooking the inserts, taking small cuts is really tricky with it especially with carbide. And I've found out that taking heavy fast cuts actually goes very well. Let the blue and glowing chips fly and get skin burns everywhere 😅
I have a very old lathe (1917) its got plain bearings, its clapped out, but it parts fine with the t shaped hss.. I run it slow with lots of oil and most importantly don't screw around, dig in and go, if you need to pause get right back out, any rubbing will work harden your material and give you fits. I think lathes that do not have a geared head but rely on variable speed dc or a vfd for most of their speed control do not have the torque to run a parting blade hard enough to avoid work hardening the material at low speed, so you are barely feeding (due to a lack of torque) and getting in trouble. at high speed your lathe is making data plate power and you are now able to feed the tool like you should. I run carbide blades at work with a 16" victor and a 13" jet, both are geared head lathes, both do fine at reasonable speeds and high feeds..
Yeah, I feel the same way every time. I just had a chance to try it in 1144, and that's even more fun because the chips break and just come flowing out of the slot.
I am not a machinist, and I’ve only had a small leave for a few years. What I have found out is you definitely need to run as close to the speeds and feeds as you can get. My lay tops out at a spindle speed at 1600 RPM the carbide cut off tool works well at that speed. I cannot seem to get a decent edge on my HSS cut off tool. I also would think that if you can adjust the spindle speed higher as your deer diameter decreases, it will cut well also. I’m stuck with the belt drive system maxing out at 1600 spindle speed. Other than that, it’s trial and error for speeds, and feeds with the smaller lays that don’t have the power or the speed.
Just today I've been experimenting with similar issues. My lathe has a power crossfeed, and my discovery was the the smooth progression of the power crossfeed gave much better results than nervously going too slow by hand. In my case it was a 1/2" wide form tool, not a parting tool.
Funny... I was gifted with an older Taig micro-lathe, and found a surprisingly decent parting tool that clamps fine in the tool post. And yes, razor edge and fast speed is the key. Yeah, a teensy bit of chatter, but not bad, and you can modulate the crossfeed pressure by hand. Darned if I wasn't getting nice square cutting with no deflection!
Ive stalled some fairly large machines over the years, most of the time its live tools or a subspindle, the answer has always been to turnnthe speed up. The thing people forget is you run out of sfm as you get to centerline and your motors run out of torque as the rpms go down. And power feed is the best for parting. And dont forget chatter is just harmonic chip breaking
One thing I would suggest is go with a squeezy bottle, like for condiments, for applying cutting oil to your parting cut. A slow drip directly onto the cut/insert meeting point does wonders. It will take more oil than the brush method, but it works WAY better.
Try without lubricant. I think it just burns and stops the blade from grabbing. This is mild steel only and aluminum , brass. I start the hss blade below center and raise it as u cut in. Again i dont even lock gibs. I just got my first carbite set with a carbite parting tool. I've yet to use it. Ill def try this method
One thing I can say is to ignore everything I commented to your last video. I must have got over-smug because everything had been going so well - like your results but at 300rpm and in "more challenging" steels like 316 stainless, 4340 etc. Then did a 10mm bar of either EN1 (1213) or EN3 (1020) crappy steel and detonated two bars on the trot. Will try your insert holder because at least it has two ends!
You can dispute the theory all you like, but you can't dispute results - Go figure. I've been going through exactly the same problem; so now I know what I'm going to try next. Thanks, Bro -
I have found (using HSS) that it helps to run the parting tool upside down with the laterh running backwards (ie with the tool advancing towards the operator). This means the chips fall downwards with gravity and are less likely to jam in the cut!
As the orchestrator of many a broken parting blade, that got my heart beating. I know carbide likes speed and pressure and I've found I can take quite deep cuts at a fast feed rate with my turning tools in my little lathe but it might take me a while to pluck up the courage to try that. As you say, it seems to work, but damn.
This my friend is one of your best videos… Science that Acquires the knowledge and feedback from other scientist’s. Thanks for such a holism truthful video. You win the internet for me today. 🇦🇺🤜🏼🤛🏼🍀🍀🍀😎☮️☮️☮️
Another thing to remember is, if for any reason, you need to stop or pause parting, get out of the cut immediately. have your hand positioned so that you can instantly reverse the crossfeed. Any amount of rubbing will cause issues getting back under the material
Seems like you had a real Eureka moment 👌 My two latest videos are about parting off. The main things I’d recommend is using power feed and not using Chinese parting tools. Maybe you should make an electronic leadscrew on your cross slide 😉 I’ve started with a Chinese blade and inserts but they have a tendency to pack up the chips in the cut and blow the insert. Then I switched to a name brand tool , no such problems anymore. Feeding harder will solve many unstable conditions and will even allow you to part with major stickout from the chuck as I’ve demonstrated. In the case of your setup going slower with a VFD is robbing your lathe of power which it needs to make the cut happen. That’s why it didn’t stall when you were parting faster.
I always apply oil using a needle point squeeze bottle rather than a brush. The brush method doesn't get much, if any, oil as the grove gets deep, and the needle oiler puts the oil deep in the groove, which is where the cut is taking place.
James, I went trough the exact same journey you made. For now, especially in stainless, go Johny, go. When I started parting on my first lathe I acted like a pussy and broke HSS blades and later carbide inserts a lot. Then an experienced machinist showed me how it was done. First attempts made me really nervous just like you or it felt unnatural to crank it in so fast. Now I'm used to it and hardly ever break an insert. Mild steel I even cut dry. And for stainless a brush works for me fine too in comparison with the other comments I read. After doing this for more than two decades you understand the feel the cut should give you. I cannot explain this feel in text but I know when I have to retract and lube up again before things go wrong now. Feed the pig is a humorous way to explain it a little. The sound is an indicator of things going well or not combined with the feel of the handwheel. I have bigger lathes than you but the way to break a parting tool is exactly the same as you showed. Chips should be short, no long curly ones. If they occur; push harder. I'm so used to parting of now that I hate to use the bandsaw... One warning; don't expect that you can cut on size . Take a little extra and turn the part over and face to size parallel. I noticed that the cut, especially on bigger diameter, drifts a little. Maybe something I'm doing wrong but I can predict it by now and correct for it too. Thank you James. Best, Job
Nicely Done! I would probably run faster than that. Twice the rpm I would think. However my feeds are generally much less. My axis servos just can't push hard enough! I use spray coolant and boy it can go horribly wrong if the coolant supply drops off. Brand name inserts can also be had in what is called low force inserts. The Sumitomo one has 30 degrees of rake so it is really trying to reduce the cutting force required, I find it works really well.
As few people said, dont use brush for oiling, it just not gonna penetrate that line you make due to centrifugal force, drip some oil there as sometimes we need to make our machines squirt a bit :]
Very cool update! Would be super neat if the ELS/motor vfd had a mode where you could ramp between start-rpm-end-rpm based on the cross slide position and/or just on a timer - know that you have to keep feeding, and it will speed up as you go to keep consistent surface speed. CNC machines do it, having a semi-dumb vfd do it wouldn't be too difficult.
I received a recommendation from a salesperson from iscar to have the tool slightly above the center because it will give less tool pressure. you will get a small lump left in the center, but you will get that anyway when you cut off a part
You can use the chip size as a guide. Generally you want small chips that break apart rather than long curly ones. It looks like the higher speed produced smaller chips, so congrats. I've always heard that carbide likes faster speeds than high speed steel, so that may also be a factor here.
I have found that rigidity in turning and parting and boring has the same effect as in drilling a drill, if you push it slow it just chatters and doesn't wanna cut but if you push it it goes really nicely same with boring bar, even brazed carbide ground to a razor sharp edge will sometimes squeal when taking very light cuts so what I used to do is either hold the bar with my fingers to make a crude "dampened" bar or I ok a heavy cut Another example is balance of a rotary part which can be horrible at slow RPM but it quickly evens out at higher RPM if the imbalance is not too big ofc CNCs all use high-ish SFM, constant uninterrupted feed and have great results... even the small CNCs that are wobbly like a wet noodle
Small lathe is a definition that depends on where you are. Industrially, anything smaller than 18 inches is considered to be small. But in the hobby world, your lathe isn’t small at all. I have a 14” and I use high speed and use a fairly heavy cut. It works all the time. A fast speed allows you to push the tool in at a good rate while not overbearing the system. The problem with running at slow speeds is that it’s too hard to control the depth of cut and so it’s easy to go a bit too fast and dig in. Make sure you’re on center. No, slightly below center isn’t a good thing. What happens is that the tool pushes the work up you get under it and push it up. Then the work springs down and you take a cut that’s too deep and it gouges the work and digs in, stopping the lathe, if you’re lucky, or breaks something, sometimes violently.
Drills, parting tools, and threading tools can be the most counter intuitive, especially with carbide. Sometimes getting that chip to form properly generally takes more speed because it isn’t as sharp and having a feed of .001” per cutting edge really ends up as a minimum.
On my small lathe, I set carbide tools scary fast and crazy depth of cut. The problem with HSS blades is that wear tapers the blade width from the cutting edge back. As the groove gets deeper, the wedge effect jambs the blade into the cut. The work around is to make a 5mm deep groove, retract and shift left or right to cut a wide groove then cut 10mm deep. Rinse and repeat. Cut a wide groove so the blade can't jamb.
yea, the slow parting advice is soo common on the web , I did it for years till i discovered higher rpm parting is soo much smoother, especially on smaller machines
I always figured upside down was safest since the jamming till gets pushed out not fed in. The whole high speed thing, I've heard that... with carbide! I've gone the slow route personally. But that's because I'm using hss. If I had another carbide insert for my holder I'd try running it faster. Either way I've ALWAYS heard that you need to stay in the cut. (I've also cut a second relief next to my part to avoid binding when going deep.)
4:22 This is the moment you chipped the tip. When machine stalls you end up with carbide welded to the workpiece. If you get stuck with a carbide during cut - force it forward manually, do not back it off! Carbide can take a lot of force when compressed but it's weak for pulling forces.
I gave up on those little tooth insert parting blades because they gave me a lot of trouble. The vibration as you cut can jar that tooth loose, and all goes to hell real fast at that point. Your surface feet changes as your depth changes, so at some point you do need to speed up. If you watch some of those fully automated machines, notice how they speed up as the diameter reduces. Another thing I do is I lock the carriage to the bed. If your tool isn't totally perpendicular, the cut can pull the carriage, so I lock the carriage. The Atlas has a cinch on it to lock up, not the feed screw. I moved over to using the T style cobalt parting blade and keep it short, like .75" to .5" stick out. The carbide parting tool I use has the cap screw that holds down the carbide tooth and I haven't had a problem with it so far.
I should also add that once upon a very long time ago I read a machinist book on how to do parting....... slow and steady, and when it didn't work it was either the tool or the machine or you...
A few people are asking about this particular parting tool. I ordered it from www.pewetools.de.
Do yourself a favor and get a FogBuster for the lathe. Way more pleasant than huffing molly-d.
Retired Engineer, machinist and shop teacher with over 50 years experience. The best advice is use the tool manufacturer's recommended speeds and feeds. Watching the second piece, you're still not feeding fast enough. watch the short chips in the first cuts, they roll up and break, that will happen at any diameter IF you use the best feed rate. You don't need the oil brush, it doesn't work, make a drip bottle if you must use lube, but water based coolant is better, it actually cools the tool and part.
Part of the issue in my experience is don't use a brush. That only gets oil to the outside surfaces on a deep parting operation. Centrifugal force slings the oil back out with very little getting to the point of cut. I typically use a squeeze bottle to drip oil at the back side of the cut and let it carry through keeping it wet. I also suspect with a VFD spindle drive at low RPM, there really isn't much torque available if you look at the torque curve for that motor.
A spray bottle of cutting oil is great for parting. Spray it onto the blade and down into the cut.
I was going to say that as well.
Need to find one of those bottles like stefan gotteswinter has with the needle tip.
Yep. Small squirty bottle with a needle on it. And soluble oil rather than traditional cutting oil - the heat from a cut like this will make so much smoke that you can't see the lathe, whereas soluble oil will make mostly steam.
McMaster has bottles like this that accepts lure lock needles. They also sell variety pack of needles so you can experiment and get just the right needle ID for dispensing the fluid
I've never used a small lathe, but in my CNC world I have learned to never hone carbide inserts and to make sure they have an appropriate load.
Early days when I first used carbide drills, the tool rep laughed at how slow I was going.....chewing up carbide tools. I quadrupled the feed rate and the tool lasted 10x longer. What an eye popping lesson.
Yes, often misunderstood about carbide inserts, they must be pushed to create enough heat at the cutting area to function. Less than that, chipping or burning of the carbide insert is assured.
This is also why altering the carbide insert in an attempt to gain a "edge" is not wise and counterproductive in every way.
That rep lost sales 😂 (but he made a friend, which is good business, hopefully!)
@@mumblbeebee6546 He lost sales in the short term, but a loyal customer in the long term.
Haven't seen the other video but i keep telling my students that if you're getting vibrations or a bad surface finish, don't slow down, increase the spindle speed and go from there.
Vibrations are usually caused at a certain frequency, you either have to go down or up to get away from it. Slowing down carbide tools isn't always the best option, carbide wants to get pushed.
Since you're not using a geared lathe, you're left with no torque advantage in slower speeds, so you gotta get it where the torque is. Increased speed will also help to overcome stuck chips or a slightly too beefy feed rate for a short moment (when hand feeding)
Some said cutting oil and a brush doesn't help and that centrifugal force won't make it cut better, but when parting off, a little bit of oil, is still better than no oil.
Another thing i like to do is to use wider parting cutters and inserts, it improves rigidity and therefore keeps the cutting geometry more stable, even on smaller lathes.
Without oil, the cut starts to growl as it gets deeper. That probably isn't a big deal, but the oil quiets it down. Though the smoke isn't ideal.
@@Clough42 use bacon grease. Makes the whole shop smell good. And it’s not a half bad lube.
@@Clough42 Parting like this with carbide is where "Low Volume" flood coolant comes in handy if your machin is capable of it - A trickle into the cut trough but not enough to spash onto the chuck and become a water park
@@bengrogan9710 A 1,5 liter cola bottle upside down with a nice 3D printed adapter for a hose/pipe with a little valve on it is enough for 'flood' coolant in this type of operation.
@@JaakkoF That's not a bad call to be honest
People underestimate these lathes all the time. They are far more capable than the usual teeny cuts shown. I learned this style of parting a few years ago. Very rewarding.
This seems like the perfect reason to add Constant Surface Speed to the VFD via the electronic spindle encoder while using the linear scales for radius input. Once you try CSS machining you will immediately see a productivity and quality improvement. In fact that is the primary reason CNC'd parts look so good.
I know nothing about turning, but I was thinking to myself that he needed a third hand to turn up the speed, to keep the surface speed, as th cutting diameter decreases
@@erik_dk842or a constant oiler freeing up a hand to be able to adjust it
A VFD will have constant RPM until parameters(overcurrent) are maxed out. Belt slip is another issue.
@@Eluderatnight A VFD will run at the speed you tell it to, if it's capable within its parameters.
Before I started out in hobby machining I'd watched a lot of TH-cam and I knew that "carbide likes to be pushed" - so, in my ignorance, I pushed it. And it worked, just as it did for you. I've never had a problem parting with carbide because I'm not afraid to send it. Power feed works well.
You also need a chuck that's in good order. Robin Renzetti had a video on trueing chuck jaws, and started out by showing what kind of deflection you can expect in a part under load if the jaws are bellmouthed. That's a recipe for parting problems.
It really does seem counter intuitive, but carbide loves to be loaded up, and you're also enjoying the higher torque from the motor at that speed. Sadly HSS won't tolerate those speeds and loads, and prefers slow and sharp. I truly believe that there's been a conflation between the two along the line that's made it into lore concerning small machines and carbide. Thanks for mythbusting James.
There’s a great book by George Thomas called Model Engineers Workshop Manual. He used to write for the british byweekly Model Engineer. There’s a chapter called “on parting off”. He devoted an entire chapter to it because on the small lathes like the myford, which is what most steam train guys had, it was the most difficult operation to do. Sometimes in a crash one could even break a cross slide or compound casting. He developed the rear inverted toolpost which is sold by Hemingway kits which solves the rigidity problem. He would frequently demonstrate parting off 1” dia mild steel at 300 rpm with hss, just to show it was easily done. The key is to stop if the chips stop curling and you have to make sure the groove doesn’t jam up with curly chips. You need lots of oil too. Btw that’s the best machining book ever. Full of wisdom and awesome tooling projects. Tee Publishing sells it. Btw parting a 5” dia piece will always be a challenge just because you can’t clear the groove.
Preso has a video series making one for his mid sized lathe that struggled with parting off, and it seemed to do wonders for him!
+1 for rear parting tool post, it gives better chip clearance (they drop out) but I found the Hemmingway design to lack rigidity and reverted to a solid lump with a blade insert as per Jame's footage at 1.29 bolted to it on centre. Also +1 for lots of watery coolant to help the cooling and washout@@climberjb
Even Stefan Gotteswinter refers to that book, I can't think of a higher recommendation than that.
My butt was puckered in solidarity.
Ha ha, I was hiding my eyes because I don't have safety glasses on!😂Good job James!
My practice is to lock the carriage when parting off. At a minimum it precludes inadvertent Z-axis motion during the parting process.
I do the same.
One thing I would recommend getting is a little needle tip oiler bottle so you can drip oil into the slot as prodigiously as you like as you part. I also use them all the time for drilling or anytime I want cutting oil in a particular spot.
Even running larger manual lathes, it took me a while to get used to carbide. Once you get used to HSS the habits are hard to break. With most carbide you can run screaming speeds and feeds and will get longer tool life. You just have to get past that initial cringe when you start a cut. Great demonstration
The Pulsing in the hand wheel and its relation to the chuck speed when doing the cut is an interesting observation. It would be interesting to do a balance check of the chuck to confirm this hypothesis. If there is in fact an imbalance an attempt to balance the chuck and thereafter do new test cuts would be interesting exercise. This could perhaps be an idea for a future video?
Perfect 👍
Thank you for sharing your experience.
Pls try this also: clamp the carriage, put some round material in your drill chuck that reaches in the borehole.
So the parted material can not fly around in your workshop.
i dont know much about small lathe´s but on my job (CNC lathe´s) i Part off with 150-250m/min , F=0.1-0.3mm/rev from 1mm blades up to 10mm as far as i know Carbide loves speed and torqe if you go to slow it will chatter or brake early. The last 1-2mm i slow down so the part dosent fly acros the country
Highly recommend full face protection, I've had carbide inserts chip and get flung all over when high speed grooving goes bad. Glad you've found the sweet spot for your lathe.
Parting is such sweet sorrow. Glad you got it worked out. I remember one time I wanted to make a washer and unwittingly picked up a piece of stainless and work hardened it to the limit. It ate my parting tool. Thanks for the video keep on keeping on.
Yeah, I generally avoid it if I can.
The thing is that when the diameter of the work goes down as you reach the centre, the surface speed and thus the chip size and cutting loads and everything else changes as well.
Carbide really is for very high speeds, large chip loads etc. and never stopping, constant flood coolant etc... so it has it's issues when running on manual lathe, since you can't provide all the parameters for it very consistently.
It's a great video, you tried it, learned something, you now know more :D
Watching those videos of high speed CNC machines i've always been amazed at how fast they cut. This video you're doing reinforces the concept of going fast.
Thanks for sharing.
yup, some tools can be pushed incredibly hard, last week i was testing some new inserts and tweaking a program for production run of thousands of parts per month... what i ended up with were surface speeds at 360m/min for roughing and 400m/min finishing... also these parts are forged into rough shape, so there is only around 1,5-3mm of material to be removed, full depth of cut, and feed rates around 0,35-0,4mm/rev roughing and up to 0,5mm/rev finishing with wiper inserts...
Thanks James.
The best way I found to cutoff is mount the cutoff blade upside down and reverse the lathe or mount the cutoff tool on the back side of cross slide if the lathe doesn't have reverse. What happens, even if you push the cutter hard, is the tool lifts up in the Aloris or other type cassette holders (holders are designed to keep the tool from dropping not rising). The extra benefit is the chips exit out the bottom of the part during cutoff operations. I've cut 1-3/4" PH17-4 stainless and O1 tool steel disks with this method without problems. I even use the cross slide advance to cutoff and I use a drip oiler and not a brush.
I made a special holder to mount the cutter upside down and I prefer using the "T" tool steel cutoff blades ~1/16" even on large diameter work. They waste less material and they're designed for razor sharp edges. On micro grain carbides I think you can get away with razor sharp edges but not all carbides work well with honing.
This is how I do it as well. The chips clear so much better.
I've had the same exact issues and I have a 14 X 44 heavy solid heavy base lathe. I went through my cross slide and tightened everything up and locked down the compound and have not had a chance to try a cut yet but I have some machinist jacks Im going to be making from 4140 and am def going to try this method.
_One thing on the reverse blade mounting I might mention; It doesn't cut any better. What it does is, if the tool binds, the blade will lift off the work, and save the blade. When cutting traditionally, and it binds, the blade digs into the work more and then you get the stoppages and damaged blade._
I'm going to be making an iron block reverse cut off but my reason is actually due to production rather than anything else.
*Also, Dave Bruneau at MSC is a good resource if you need help with cut off blades. I talked to him about my cut off woes and he directed me to a new blade series by ISCAR and I got it but as I said I haven't used it yet.*
D
I like to use water soluble oil with a drip feed when I cut off, especially larger diameters. I part using a steady rest when possible, as my chuck is not what it once was. I will also use a clamp I crafted from an aluminum ring to place force on the chuck jaws. You really get everything out of that hobby lathe that is possible. Nice job!
Contrary to everything I’ve been told the past 30 years AND I’ve never had much joy at parting....thanks!
Yes James,
It works and works well, consistently!!!! I theorize that the increased RPMs actually help in the chip evacuation by throwing them further away from the cut immediately after being shaved off, thus not allowing them to remain in the small space closer to the decreased diameter and with that increased room to move outwards from the centrifugal forces they just dont have time to pack up together and increase friction and jam up. There's a load of physics principals that could probably explain it all , but it all comes down to.... if its not broke dont fix it. Just saying !!!!
Excellent vid amdsure it has opened a lot of eyes. Keep up the great work.
Don
it has more to do with surface speed, since carbide doesnt like low speeds at all, even 100m/min he used is on the lower end of the scale, some inserts i used in the past liked speeds around 120m/min in stainless and slow down to around 70 in the last couple of mm where the part snaps off, speeds around 180-220m/min were also good for steels similar to 1018 with a slow down to around 450rpm for final break off of the part...
Thanks James for giving this a try and motivating the rest of us to try!
My experience is that WD40 in a can +long straw is better than oil. Also 2mm wide insert works better than 3mm (my lathe is 1300 kg~ 3000lbs). Feeding by hand is better than autofeed. The feed has to be such that the WD40 doesnt steam. I set up the rpms as high as possible, but low enought that the centrifugal force doesnt spray WD40 all over the place (which for most applications is 600 rpm). Also when machining the weldable steels they tend to work harden, and there is no clear conclusion under which conditions. This work hardening is the reason why auto feed doesnt work and will break the insert When the steel work hardens it is an art to take this layer off, and then for some time the tool cuts like a charm, and then the surface workhardens again.
Unless I missed something you installed a one horsepower VFD and motor on your lathe. Since the motor is rated for 60 Hz and last I knew your VFD was set to max at 120Hz. Which I would guess means that above 60Hz motor torque would drop off. So between 6Hz and 60Hz the motor torque would be fairly constant. But because horsepower is torque times speed running below 60Hz means your hp would drop off proportionally also.
Cutting metal on a molecular level is braking electron bonds similar to melting. If the metal chip can not get away from the cutting tool fast enough then the chip melts, piles up and re-solidify on the cutting tool. Now it will take more force to continue the cut not only because of the larger mass required to cut but also the re-solidified material has tried to weld itself onto the cutting tool. Thus a recommended minimum cutting speed for steel. This also means a minimum horsepower requirement per cutting width. So for larger diameter parts it would be advantageous to increase the reduction reduction ratio between the motor and the spindle to be able to utilize your available horsepower.
Not having a lathe, and living vicariously through you and Quinn -- it looks like carbide just wants more and faster, regardless of how much and how fast you're already going. Yay/nay?
pretty much, you can go too far for carbide but on a hobby machine that aint happening
the point thaat is counter intuitive is that Carbide is too hard to be reliably "Sharp" - thus meaning that a HSS too can Shave were Carbide has to "Rip"
The tool pressure needs to be high enough that the Carbide doesn't lift the chip and break off to the rip and fall into the hole - leading to guarenteed chatter
@@bengrogan9710 Could it be that it creates a hill like a bulldozer instead of digging in and then slides over the hill and then slams into the surface after riding down the downhill side ? Maybe it also stops cutting and starts sliding and everything gets deflected, building up energy, until the pressure gets high enough to suddenly dig in really deep.
@alexandern8hgeg5e9 1st part you have backward, it's not that the tip rides over it - the chip is formed with enough strength that it levers itself away as it rolls onto the tool: have you ever felt yourself lifted by the arms and felt your legs go forward into the gap? That sort of effect.
For the 2nd part, yes that is why carbide needs higher tool pressure to engage to begin with
It’s the old saying “If you’re not cutting your dulling”. And one type of chatter is called “cut rub cut rub”. One old solution to stopping chatter is adjust your “speed and feed”. That doesn’t mean that you always adjust down. It means you adjust it until you get something that works better.
My lesson from Mr Pete was to make certain the blade is at right angles. I use a square or 123 block against the chuck, but Abom indicates his in and that's probably a better practice.
Other hard lessons:
1. Cut or don't cut, but do not linger. Either cut aggressively or pull out of the cut.
2. Angled inserts (GTL or GTR) sound like a good way to control where the final nubbin winds up, but in tough parting jobs they eill twist the today out of position. Pinning the tool post so it is physically blocked from rotating is high on my agenda.
3. Flood coolant helps a lot with keeping things under control.
4. Turn your VFD all the way down (mine has a lower limit of 36Hz) and gradually increase the speed as the cut progresses.
Aggressive cuts work, even in my tiny little Taig. On my 13x40 lathe, power feed is your friend.
One thing i noticed in your first video is that, judging from the chip formation, the blade isn't quite square. The chip should form a watch spring, not a corkscrew,if the tool is perfectly square.
Signed: parted 2.5" SS bar and lived to tell the tale.
Since you have a VFD, next time i would suggest what works in our CNC job shop, even higher surface speeds, if you cant squirt coolant right into the cut, ditch the brush, instead try to gradually increase rpm as the parting diameter shrinks to maintain the surface speed, then when you get to the last few mm (4-6mm) slow it down to around 300-500rpm and finish the cut
I went to school to be a machinist. I have years of manual lathe experience. I have had that handle pulsing you described @ 9:32 on multiple lathes from 15 to 20 inch swing gear head lathes. I have a Grizzly G0602 but it is still crated. My experience has been to feed in aggressively at a content speed almost to the point of feeding faster than it's cutting. And don't stop until you're through. But I never ran over about 500 rpm on say 2 in. (50mm) material. Oh and the lathes I ran didn't have any coolent. I just cut it dry. I never used cutting oil much. Yes it is harder on the tools like that but I wasn't paying for them either. On the HSS parting tool you showed. I noticed it was burnt from grinding. You never want to burn your HSS. Quench it often and early.
Supposedly, such moderate burning has no effect of the temper of HSS.
I might just give this a try ! I have NEVER had a successful parting off (over many many years) - particularly in aluminium - as you say, the bandsaw is your friend 🙂
I have done the same "trip". Started with HSS parting tools and low revs, learned to grind a concave cutting edge to get thinner chips, but always hated parting.
Changed to carbide parting and realized that I could raise the revs and parting gets easier and easier.
I´m using oil on a brush as long as the cut is shallow and then I use cutting oil in a spray can when the cut gets deeper because the brush simply doesn´t get that deep. I try to add the cutting oil as close to the parting tip as possible because the centrifugal forces will throw the oil out of the cut otherwise. The reason I start with oil on a brush is simply because it is so much cheaper than spray can oil.
Yeah. Since I didn't know any better, that was I was doing all the time. Never had any real problems. So: thumbs up!
Carbide manufacturers/tooling reps have always told me, carbide loves fast and consistent cuts. When it comes to coolant or cutting oils, flood it or run it dry. Their advise worked for me. I played with mist coolant on the lathe years ago and it worked quite well.
I remember first using a manual lathe. It can definitely be intimidating.
Bump your spindle speed up a little bit more and keep your feed about the same and I think you’ll see even more improvement.
I've worked at loads of different machine shop's in general people do run speeds way too slow and a lack of understanding about having a rigid set up also doesn't help. Carbide tool love fast speeds and heavy feeds. I once saw a tool company demonstrate ceramic tips. Bloody hell, 2500 rpm cutting like butter curls only blue in colour more amazing workpiece remains cool.... What an eye opener for a young apprentice back in the 1970s my firm was at the cutting edge of technology. This was a 2" hole from solid in a 6" billet of steel..... At that time the tool rep only had 4tips to try.
I've almost given up parting... I always have the same issues as you. Thanks for the idea, I'll give it a go 🤞
I have good luck using a needle oil bottle. It puts the oil right at the cut.
Good idea.
not many can deal with their own blind spots that good.
congratulations !
Thanks for the video!! It was quite an eye opener!!! My uncle worked as a lathe machinist his whole life in the aerospace industry. He always told me that carbide likes speed. However to prevent wear on my lathes bearing, I usually don't run it above 500 rpm...also the chuck spinning at 1000 rpm during a cut it scary...guess I have to give it a shot!
I have that same lathe and did the variable speed conversion from your videos, and I don't have a problem parting. I have had some experiences when my lathe tool was too low and the material kind of jumps over center and hangs up, but when my tool height is right I have no trouble. Happy for ya' though! Forget that hacksaw stuff!
Run a little lathe from our showroom all the time these are about the same numbers I’ve been running for good results for awhile glad you found something that worked 👍
Impressive! I wonder if things would improve even more if you locked the carriage to the bed.
Wow! Like you, my parting experience has been much the same. And the advice I’ve been given is similar - slow and light. I’m going to try this out on my lathe tomorrow morning!! Thanks so much for sharing this tip. I’m amazed!
I have a smaller lathe, and I've done some very high speed turning with carbide tools. It's not quite the tightrope act that a parting tool is, but it still feels terrifying. I wore a full face shield. That said, I've seen someone using the same lathe I've got to turn hardened steel with carbide bits at max speed. That's not one I'll be trying any time soon. In the video I saw, the chips came off like the part was pissing magma.
I was taught to set the parting tool a smidge above the centerline to help avoid grabbing. The tool will spring down a bit under load, so when you set it (without load), just set it above the center. Cutting with the edge of the tool lower than the center of the part pulls the tool into the cut, and the slack on the crosslide will make it easy for the tool to move forward all by itself. If anything, you probably want to be a little higher than center under load
I set it just slightly above center, with the assumption it would flex. I've seen the opposite advice as well, and had some success with it. I think all of the variables interact and there are multiple ways to succeed. I'm just happy to have found one. :)
I tried far higher than usual RPM parting today on my micro-lathe with a HSS blade. Much easier than usual. I’m bemused by this result, but I’ll take it as a win.
This makes me wonder if you could add a constant surface speed function to your electronic lead screw control. If you could set a surface speed on your interface, figure out a way to get the x position from the DRO, calculate the required RPM, and actively adjust the VFD then you could maintain a constant surface speed as you change the X position. My Trak lathe does this and it’s amazing for part offs.
Thank you so much because I have had the same problem that you were having. I watched this last night this morning I went out and tried it, like you eye protection full face mask expecting it to explode. It worked fantastic. Again, thank you
I've been meaning to buy one of these carbide parting tools. This persuades me, thanks. After struggling parting with his tools, this does seem insanely fast, but it makes sense - faster cutting is what the carbide tools will have been made for on cnc's
Youre correct. The growling at the end is the reduced surface speed. Never hone the edge, it's designed that way for a reason. And feed is your friend. Too sharp and too slow is a recipe for chatter. Settin a touch below center helps to.
Well I am surprised.
At 500 rpm I thought no, best slow it down a bit.
As you increased rpm I cringed and ashumed you were joking.
I was really stunned when you started parting at 1000 rpm.
I was even more stunned when it worked.
Thanks for trying the great anti comfort-zone YT advice & thanks to those knowlegable YT advisors.
I tried speeding up last month. After referencing the speeds and feeds in my handbook, I did some parting with my HSS part off tool and was also pleasantly surprised.
I'm not all that knowledgeable with carbide myself but one factor I've read more than once is that they can't normally be babied with a very light chip load. As you noted the cutting edge is not razor sharp. And honed or not the first part of the top at least would have hand a touch of that edge left. And what I've read is that for the chip to form correctly, self eject and not jam in the cut that the cut has to be a touch on the aggressive side. And this video seems to support that idea. Mind you I do all my parting with a couple of HSS blades. So what do I know....
I do use 'professional' named inserts and blades. And never experienced any problems parting. So seeing this, and others almost being scared of parting is kinda hilarious 😂. But... It also shows that you shouldn't buy cheap parting tools. I do use power feed most the time, and only use coolant in stainless steel. The oil/brush is only making smoke and nothing else. A carbide insert really like being ~1000c° 😅
But as you also mention, pressure is key. You need to push hard. And after a while you can easily hear and see (or feel) if something is wrong.. and you need to slow down a while. It's key the chips to outwards. And that's what the pressure is all about. New chips push the old outwards.
Having the blade under, also causes the blade to have a tendency to being pulled inwards. Always 100% in center height 👍
Best regards
James: I had problems with parting for 20 years on my JET 9x20. tried the 4 bolt compound mount but that didn't fix it. It did improve it. My final solution was a disk that replaced the
"stand thing" that had the degrees on it. The disk is tall enough to put the compound up at the
same height. I clamp it to the four corners as the disk is the full width of the topslide. I engraved the degrees on it and it in turn it is mounted to the bottom of the compound with 4 additional screws plus the original three. I put a pin in the bottom of the disk to function like the original. still have to get the compound gib tight too. Let me know if you need a picture to
visualize. John Orr
That is so my experience in parting. I will try that too as I have parts of that nature to make for a friend. All precautions taken, for sure.
I started using the auto cross slide on my Logan and the parting went way better than before! I think the trick is to keep constant pressure I guess.
It made a big difference for me when I stopped being a fanny and used the power crossfeed. Knowing you, Im sure you could fit a stepper motor on the back side of the cross slide and have an els-cs. Then you would be dangerously close to having a cnc lathe lol.
Also, couldn't help but notice you not locking carriage. Which leads me to believe you might be crazy...
Im a mechanic and at work we have an old very sloppy and worn lathe, the whole tool holder can easily jump up and down 3mm or more and cooking the inserts, taking small cuts is really tricky with it especially with carbide.
And I've found out that taking heavy fast cuts actually goes very well. Let the blue and glowing chips fly and get skin burns everywhere 😅
I have a very old lathe (1917) its got plain bearings, its clapped out, but it parts fine with the t shaped hss.. I run it slow with lots of oil and most importantly don't screw around, dig in and go, if you need to pause get right back out, any rubbing will work harden your material and give you fits. I think lathes that do not have a geared head but rely on variable speed dc or a vfd for most of their speed control do not have the torque to run a parting blade hard enough to avoid work hardening the material at low speed, so you are barely feeding (due to a lack of torque) and getting in trouble. at high speed your lathe is making data plate power and you are now able to feed the tool like you should. I run carbide blades at work with a 16" victor and a 13" jet, both are geared head lathes, both do fine at reasonable speeds and high feeds..
Ok, I can’t wait to try that!! Although I feel like it’s just not gonna work even though I just saw it
Yeah, I feel the same way every time. I just had a chance to try it in 1144, and that's even more fun because the chips break and just come flowing out of the slot.
I am not a machinist, and I’ve only had a small leave for a few years. What I have found out is you definitely need to run as close to the speeds and feeds as you can get. My lay tops out at a spindle speed at 1600 RPM the carbide cut off tool works well at that speed. I cannot seem to get a decent edge on my HSS cut off tool. I also would think that if you can adjust the spindle speed higher as your deer diameter decreases, it will cut well also. I’m stuck with the belt drive system maxing out at 1600 spindle speed.
Other than that, it’s trial and error for speeds, and feeds with the smaller lays that don’t have the power or the speed.
Just today I've been experimenting with similar issues. My lathe has a power crossfeed, and my discovery was the the smooth progression of the power crossfeed gave much better results than nervously going too slow by hand. In my case it was a 1/2" wide form tool, not a parting tool.
Funny... I was gifted with an older Taig micro-lathe, and found a surprisingly decent parting tool that clamps fine in the tool post. And yes, razor edge and fast speed is the key. Yeah, a teensy bit of chatter, but not bad, and you can modulate the crossfeed pressure by hand. Darned if I wasn't getting nice square cutting with no deflection!
Ive stalled some fairly large machines over the years, most of the time its live tools or a subspindle, the answer has always been to turnnthe speed up. The thing people forget is you run out of sfm as you get to centerline and your motors run out of torque as the rpms go down. And power feed is the best for parting. And dont forget chatter is just harmonic chip breaking
One thing I would suggest is go with a squeezy bottle, like for condiments, for applying cutting oil to your parting cut. A slow drip directly onto the cut/insert meeting point does wonders. It will take more oil than the brush method, but it works WAY better.
Try without lubricant. I think it just burns and stops the blade from grabbing. This is mild steel only and aluminum , brass. I start the hss blade below center and raise it as u cut in. Again i dont even lock gibs. I just got my first carbite set with a carbite parting tool. I've yet to use it. Ill def try this method
One thing I can say is to ignore everything I commented to your last video. I must have got over-smug because everything had been going so well - like your results but at 300rpm and in "more challenging" steels like 316 stainless, 4340 etc.
Then did a 10mm bar of either EN1 (1213) or EN3 (1020) crappy steel and detonated two bars on the trot. Will try your insert holder because at least it has two ends!
always been told that carbide needs to be run hard and fast, but it's never worked on parting for me. I'll try it harder and faster next time. Thanks
Goes to show that the internet is full of really great advice. Just have to sort the wheat from the chaff. Great video, thanks James.
You can dispute the theory all you like, but you can't dispute results - Go figure. I've been going through exactly the same problem; so now I know what I'm going to try next. Thanks, Bro -
I have found (using HSS) that it helps to run the parting tool upside down with the laterh running backwards (ie with the tool advancing towards the operator). This means the chips fall downwards with gravity and are less likely to jam in the cut!
As the orchestrator of many a broken parting blade, that got my heart beating. I know carbide likes speed and pressure and I've found I can take quite deep cuts at a fast feed rate with my turning tools in my little lathe but it might take me a while to pluck up the courage to try that. As you say, it seems to work, but damn.
This my friend is one of your best videos… Science that Acquires the knowledge and feedback from other scientist’s.
Thanks for such a holism truthful video.
You win the internet for me today.
🇦🇺🤜🏼🤛🏼🍀🍀🍀😎☮️☮️☮️
The ending with the music was awesome it was pretty badass
Another thing to remember is, if for any reason, you need to stop or pause parting, get out of the cut immediately. have your hand positioned so that you can instantly reverse the crossfeed. Any amount of rubbing will cause issues getting back under the material
Seems like you had a real Eureka moment 👌
My two latest videos are about parting off. The main things I’d recommend is using power feed and not using Chinese parting tools. Maybe you should make an electronic leadscrew on your cross slide 😉
I’ve started with a Chinese blade and inserts but they have a tendency to pack up the chips in the cut and blow the insert. Then I switched to a name brand tool , no such problems anymore.
Feeding harder will solve many unstable conditions and will even allow you to part with major stickout from the chuck as I’ve demonstrated.
In the case of your setup going slower with a VFD is robbing your lathe of power which it needs to make the cut happen. That’s why it didn’t stall when you were parting faster.
I was with you on what was going to happen. I'm shocked and very happy more speed and feed work better.
I always apply oil using a needle point squeeze bottle rather than a brush. The brush method doesn't get much, if any, oil as the grove gets deep, and the needle oiler puts the oil deep in the groove, which is where the cut is taking place.
James, I went trough the exact same journey you made. For now, especially in stainless, go Johny, go. When I started parting on my first lathe I acted like a pussy and broke HSS blades and later carbide inserts a lot. Then an experienced machinist showed me how it was done. First attempts made me really nervous just like you or it felt unnatural to crank it in so fast. Now I'm used to it and hardly ever break an insert. Mild steel I even cut dry. And for stainless a brush works for me fine too in comparison with the other comments I read. After doing this for more than two decades you understand the feel the cut should give you. I cannot explain this feel in text but I know when I have to retract and lube up again before things go wrong now. Feed the pig is a humorous way to explain it a little. The sound is an indicator of things going well or not combined with the feel of the handwheel. I have bigger lathes than you but the way to break a parting tool is exactly the same as you showed. Chips should be short, no long curly ones. If they occur; push harder. I'm so used to parting of now that I hate to use the bandsaw... One warning; don't expect that you can cut on size . Take a little extra and turn the part over and face to size parallel. I noticed that the cut, especially on bigger diameter, drifts a little. Maybe something I'm doing wrong but I can predict it by now and correct for it too. Thank you James. Best, Job
Nicely Done! I would probably run faster than that. Twice the rpm I would think. However my feeds are generally much less. My axis servos just can't push hard enough! I use spray coolant and boy it can go horribly wrong if the coolant supply drops off. Brand name inserts can also be had in what is called low force inserts. The Sumitomo one has 30 degrees of rake so it is really trying to reduce the cutting force required, I find it works really well.
As few people said, dont use brush for oiling, it just not gonna penetrate that line you make due to centrifugal force, drip some oil there as sometimes we need to make our machines squirt a bit :]
Very cool update! Would be super neat if the ELS/motor vfd had a mode where you could ramp between start-rpm-end-rpm based on the cross slide position and/or just on a timer - know that you have to keep feeding, and it will speed up as you go to keep consistent surface speed. CNC machines do it, having a semi-dumb vfd do it wouldn't be too difficult.
I received a recommendation from a salesperson from iscar to have the tool slightly above the center because it will give less tool pressure.
you will get a small lump left in the center, but you will get that anyway when you cut off a part
You can use the chip size as a guide. Generally you want small chips that break apart rather than long curly ones. It looks like the higher speed produced smaller chips, so congrats. I've always heard that carbide likes faster speeds than high speed steel, so that may also be a factor here.
I have found that rigidity in turning and parting and boring has the same effect as in drilling
a drill, if you push it slow it just chatters and doesn't wanna cut
but if you push it it goes really nicely
same with boring bar, even brazed carbide ground to a razor sharp edge will sometimes squeal when taking very light cuts so what I used to do is either hold the bar with my fingers to make a crude "dampened" bar or I ok a heavy cut
Another example is balance of a rotary part which can be horrible at slow RPM but it quickly evens out at higher RPM if the imbalance is not too big ofc
CNCs all use high-ish SFM, constant uninterrupted feed and have great results... even the small CNCs that are wobbly like a wet noodle
Another suggestion, you need to get some more oil/coolant down in there to keep that insert cool.
Small lathe is a definition that depends on where you are. Industrially, anything smaller than 18 inches is considered to be small. But in the hobby world, your lathe isn’t small at all. I have a 14” and I use high speed and use a fairly heavy cut. It works all the time. A fast speed allows you to push the tool in at a good rate while not overbearing the system. The problem with running at slow speeds is that it’s too hard to control the depth of cut and so it’s easy to go a bit too fast and dig in. Make sure you’re on center. No, slightly below center isn’t a good thing. What happens is that the tool pushes the work up you get under it and push it up. Then the work springs down and you take a cut that’s too deep and it gouges the work and digs in, stopping the lathe, if you’re lucky, or breaks something, sometimes violently.
Drills, parting tools, and threading tools can be the most counter intuitive, especially with carbide. Sometimes getting that chip to form properly generally takes more speed because it isn’t as sharp and having a feed of .001” per cutting edge really ends up as a minimum.
On my small lathe, I set carbide tools scary fast and crazy depth of cut. The problem with HSS blades is that wear tapers the blade width from the cutting edge back. As the groove gets deeper, the wedge effect jambs the blade into the cut. The work around is to make a 5mm deep groove, retract and shift left or right to cut a wide groove then cut 10mm deep. Rinse and repeat. Cut a wide groove so the blade can't jamb.
yea, the slow parting advice is soo common on the web , I did it for years till i discovered higher rpm parting is soo much smoother, especially on smaller machines
I always figured upside down was safest since the jamming till gets pushed out not fed in. The whole high speed thing, I've heard that... with carbide! I've gone the slow route personally. But that's because I'm using hss. If I had another carbide insert for my holder I'd try running it faster. Either way I've ALWAYS heard that you need to stay in the cut. (I've also cut a second relief next to my part to avoid binding when going deep.)
4:22 This is the moment you chipped the tip. When machine stalls you end up with carbide welded to the workpiece. If you get stuck with a carbide during cut - force it forward manually, do not back it off! Carbide can take a lot of force when compressed but it's weak for pulling forces.
I gave up on those little tooth insert parting blades because they gave me a lot of trouble.
The vibration as you cut can jar that tooth loose, and all goes to hell real fast at that point.
Your surface feet changes as your depth changes, so at some point you do need to speed up. If you watch some of those fully automated machines, notice how they speed up as the diameter reduces.
Another thing I do is I lock the carriage to the bed. If your tool isn't totally perpendicular, the cut can pull the carriage, so I lock the carriage. The Atlas has a cinch on it to lock up, not the feed screw.
I moved over to using the T style cobalt parting blade and keep it short, like .75" to .5" stick out.
The carbide parting tool I use has the cap screw that holds down the carbide tooth and I haven't had a problem with it so far.
I should also add that once upon a very long time ago I read a machinist book on how to do parting....... slow and steady, and when it didn't work it was either the tool or the machine or you...