In MY experience: 1) Proper depth of cut can prevent surface damage by wrapped up chips. Having a DOC that gets the chips to properly brake will minimize the risk of smeared/scratched surface finish. 2) Some materials will have perfectly fine surface finish with a wide range of DOC. Some materials tend to have better surface finish with a proper (deep enough) DOC. 3) Most of the time cutting a bit deeper then nose radius depth is deep enough. Sometimes for best finish 2x nose radius depth is needed. 4) Super shallow cuts with extremely high cutting speeds are almost always amazing finish.
I will add that tiny depth or cuts/spring passes can bump the tool off and on the cut due to the elastic deformation of the workpiece material underneath causing it give in (also softer materials will take more deformation until they "fail" into a chip, so they will most likely leave hangers and boogers if the doc/fr aren't enough to go past it), and won't produce the shiniest surface possible, even with the sharpest light/fine turning grades available. With that said, on steel you can take a 0.01mm depth of cut with a really sharp, fine turning ground insert (even better the honed/lapped tolerance grade E), and even if it doesn't get scratched or bumpy, it will still not be as reflective (and probably a bit rougher along the cut) due to the reduced cross section of the chip, not conducting/spreading heat in the same way, as well as the minimal cutting pressure being inadequate to produce the work-hardened, compressive residual stress layer, that gives the machined material the shiny surface (due to the material under the shear zone being prestretched at it's yield point and not being able to take enough extra deformation to leave hanging crud) and some forged like qualities (that's why even stress relieved materials will warp when machined with cutting tools versus EDM etc)
Just a quick English lesson ....the word is BREAK .....not BRAKE. Also, what you are completely missing is the word SHEAR ....which is what this is all about. I also point out that nothing has been discussed about the insert .....NOTHING. You mention "2x nose radius depth is needed". This is very misleading and in some cases incorrect. The condition of the material is what will dictate what is needed. Every hear of "Denitool"? Look it up ...and even better ...try this product. You WILL NEVER look at inserts the same way again. .
I do production, and for chip control, and tool life, I always take right above tool radius, and with enough feed to ensure chip breakage(but of course stay within surface spec). I found that if I only take 0.2mm radial cut for a finishing pass with a R0.4 nose radius. After 20-50 parts, I'll start to see a flat spot on the insert radius(plastic deformation), leading to a faster deterioration of the surface quality. Meanwhile, if I take a 0.5-0.8mm radial doc, the insert will last me 200+ parts, without any nest building, or a big surface quality decrease.
Why didn't I think of doing an experiment like that years ago....very helpful. Low carbon steel is always a challenge to get a good finish, especially on a manual lathe. Hate when you take that last pass and the finish goes bad on you.
@@gangleweed I have a particular tool that leaves a very good finish in mild steel but it only works starting at 4mm diametral depth of cut. fun times when I need to turn a 20mm bar into 16mm + - 0.01mm in one single pass, at least I don't have to sand to get an acceptable finish.
@@user-tw9io9nz2m Here's a tip for you.....if you want to get a " chrome" plated finish on any mild steel try doing a finishing cut at .06mm deep and run the lathe at 60 rpm if you can go that slow and use coolant......the curl that comes off will be like ally foil......works for any other metal too. I use a tool that looks like a parting tool but has a 6mm wide tip face, honed sharp......keep the tool face dead square to the work piece and you can use a fairly fast feed to save time. Using that method I've formed large radii with a form tool on my old capstan lathe many years ago.
@@user-tw9io9nz2m Yep, I can guarantee that if you take a shallow finishing cut using a slow speed with a broad tool the finish will be like chrome plate. If the tool is shaped like a parting tool and honed sharp......6mm wide is good........it peels off a sliver like fine foil......the feed rate can be quite coarse as the finish is determined by the tool width, but it must be dead square AND DEAD ON CENTERE to the work piece or you'll get cyclic grooves as it cuts........using it on brass is awesome.......as long as the work piece is kept lubed with coolant the finish will be shiny.
Thank you for taking a methodical approach to this and for sharing your results; there's no end of permutations but having an idea of where to start helps a lot.
"But what about depth of cut?" That was the question after watching your last video. Thanks for that. Good practices for preparing for jobs in different materials using different tools.. Excellent video.
I like how you made each pass become 10 separate tests with the varying depths, rather than doing them one at a time. Very clever. I'll have to remember that one for sure. Maybe a may not remember the results here --- but I'll remember how to run the test and get my own results next time. Great stuff
Great video you open my eyes up and you have learned through your experiences and it’s great that you’re sharing them because I’m going to look at things a little differently
The main factor for a good finish, if we are talking about steel - like in your video, is cutting zone temperature. Which your tests showed very well. Everything that increases that (to a certain point) will increase it, since the chip will shear much cleaner from the material. Coolant won't make a large difference or only at very low SFM. A used insert (not broken) will almost always make a better finish than a new one, since isn't as sharp and creates more temperature. That goes for everything that increases it, like: "dull" tool geometry (thats why its always shiny after roughing) , higher SFM, higher DOC, higher feed, tougher material etc. Of course every grade of steel is different and requires certain parameters. But generally something like 1018 will only finish good at roughing cuts or very high SFM, while 4140 won't be much trouble to get a good finish. (but again, the toughness creates way more temperature, so it helps a lot by itself)
I can add a reference book to the discussion. I am a hobbyist, and have only read a little bit of this book. "Metal Cutting Principles", second edition, by Milton C. Shaw, copyright 2005, Oxford University Press Excellent experiment.
I agree with you. Built up Edge happens because of cutting zone temperature being too low. From what I've seen of materials under the microscope, the poor surface finishes seem indicative of material smearing.
My only disagreement is on "coolant" (I highly prefer the term cutting fluid). Generaly cutting fluid reduces friction from the chip with the cutting face (the hottest zone) so in effect tool heat, while still allowing to maintain enough heat in the shearing zone. In my experience cutting fluid (even a measly oil mist) makes a big difference in reflectivity, even with cutting speeds well above the shiny zone (with no stuck built up edge, no hangers from the material elastically deforming more than the doc/fr, no chewed up finish from chips bumping back on the workpiece), it will still increase the reflectivity of the surface by preventing rapid oxidation of the material under the cut from getting exposed to air at high temperatures. Also it's the only way to get a completely smooth, mirror finish on mild steel when milling... without cutting fluid it just goes from a dull grey to having burn marks if you keep pushing the speed but it will never look shiny and crisp without it (width of cut won't do much either)
@@Sketch1994 usually turning (or all operations with continues tool engagement) always are done with coolant or cutting fluid. Of course it helps in the long run and will improve the finish, but not to a level where too low SFM or other bad paramters are compensated. Regarding milling on mild steel: We do most of our milling dry. (10 to 20x more toollife compared to high pressure TSC) Exceptions for side finishing, thread milling, deburring and form tools. Mostly 1018 and 1045. Best way to get got surfaces is just to use an insert with a long wiper edge and running at least 650 SFM. Seco Square 6 shoulder mills work extremely well, or double Octomill with M11 geometry. (all dry aswell) To get almost mirror like finishes, try Cermet tooling with around 1000 SFM. But spindle alignment etc. need to be spot on.
Thank you so much for this superb follow-up video - it answered many of the remaining questions I had at the end of the first video. I now I have something definitive to attempt to replicate on my (slightly worn out) HLV-H - or at least understand if I’ve reached the limit of what’s possible without a rebuild.
What a great demo, I’d like to say I’d show this to some on the younger lads at work but to be honest most of them aren’t interested in learning on my opinion. However i definitely enjoyed it.
Very cool tests.. I learned a lot. It answers so many "what if" questions. I see why you are saying SF instead of spindle RPM; because depending on the diameter of the work, the SF changes a lot, at the same given RPM. It's crazy to see so many variables in such a simple and straight forward test; and we haven't even talked about different tooling HSS vs carbide- or even all the variables of turning different materials, such as HC steel vs copper vs brass vs stainless vs aluminum, etc... I feel like I know just enough to realize there are so many things that I don't know. lol.
You also forgot to mention machines and the difference in setups. This is one of the reasons I don't often mention speeds and feeds in my videos. There are so many variables that what I do probably wont work for you the same. What I want to encourage with these type of videos Is. People should make tests with their own equipment, tooling and setup to get the correct cutting conditions. That said this might give some idea where to start.
Love the content! - really interesting to see the different finishes! Sure there is a recommended depth, Cutting speed and feed for every insert - but these comparisons really help when your machine is not capable of a high enough surface speed or a fast feed. Could get you out of a tight spot when chasing some tough drawing specs. Thank you for this :) Might be a good idea to include pictures from your Phone in the Video to help visualize the surface - the gopro isn't too happy with this close focus. Greetings from Germany
Thanks Peter! Really notice the DoC effect at these feeds. Your machine looks like it wants aggressive cuts with light cuts and faster feeds for finishes, and the 800 feed does work well.
Great video Peter. I wonder how many people read the back of their insert packets. Things really go better when you follow the manufacturers recommends surface speed and depth of cut.
Really interesting and well executed test! Makes me wonder if the inertia of the material coming off has something to do with the quality of the finish, and what the graph would look like if we could plot surface finish against say the mass flow rate off the part at various surface speeds.
Great video does appear to be 1018 i began running a okuma in 1988 and have always left 0.01 on dia 0.002 on faces tor most materials i do increase finish depth for smaller diameters if i max rpm is reach
Cermet inserts also work great for steel. Mitsubishi MP3025. They also have a wiper geometry so you can feed double the feed and achieve same surface finish .
Very interesting, thank you. My little lathe can't hit those speeds. I have found that running coolant makes a marked difference to the finish I can achieve.
Great information. Inset sharpness has a big effect when taking whisper cuts on my little Super 11. I hand lapped an insert to make it very sharp and finish on a whisper cut was much better but they don't stay sharp long. Maybe diamond tooling would hold and edge longer.... JMHO....
Like I said in the video. I have never done this test before. I had to think of a way in a video how to demonstrate it. This is what I came up with. I pretty much knew what would happen from experience. It did pretty much what I expected. Thanks!
This and your surface speed video are great! Years doing this and I've never run a test like this. Its so great to see it side by side in a controlled way. Do you have any plans to continue with similar testing for us? Im trying to think of other things of interest...tool life is probably too tedious to test scientifically, maybe chip control, different insert grades or chipbreaker geometries, milling tool paths - old school slotting vs adaptive / trochoidal....not sure if there is enough meat there to make a full video, just throwing out some ideas in hopes of seeing more testing :-D
Most interesting! Thanks! I'm wondering if coolant or cutting oil has any effect on surface finish. Might be interesting to rerun one of the ones that showed variation (maybe 400/.005, I think was one) with coolant and see if the result is the same.
Would be interesting to see a test with a profilometer on one of those pieces with a visible difference in surface finish on each step. Does a better looking finish mean a better measured finish?
In short: No. Our eyes tend to prefer shiny while measurements are based on the actual surface profile. That said an experienced person can often judge if a surface is "good" or not. But it doesn't replace a measurement. And there are also multiple ways to measure that can't be compared to each other (Ra, , Rq, Rt, Rmr...)
It doesn't, it can look good to our eye and be awful when actually measured. We as humans tend to think that shiny and homogeneous looking equates to a good finish but that can be misleading. Guys that have been doing this for a few decades though can usually eyeball what kind of finish it is and in my experience be correct about it most of the time once it has been actually measured.
I've always held to the idea that minimum depth of cut should match the nose radius of your finishing tool. I prefer to double it and crank the surface footage up. My standard finisher has a .4mm nose radius, so I typically write programs with a U-.032 and G96 S1500. The shop I work for strictly runs haas machines. That machine can handle so much more, especially with a .032 nose radius. A cut at .062 deep at 600-800 sfm (I'd max the spindle out if I were running it) would shine like a diamond. I also just happen to love the sound of chips spraying the door. It's the sound of my people.
Nice I use an .008 thou rad finish at 656sfm and .0036 feed around .005 doc . I did tests just like your doing within the manufacturer’s recommended speeds. I would love to have one of the integrex machines. maybe one day…
We've started doing deeper finising cuts to reduce the chip stringing, if the setup can take it we do 1/8th inch off the diameter for a finishing cut with a 1/32nd nose radius insert. Perhaps going deeper could help you as well.
A couple of important points to add along with the video (in no particular order and with way to brief explanations): (Post updated with geometry below) It is very important to differentiate between visual and measured finish - Look at what the customer specified! (Most common is measured in Ra, if it "looks" shiny or not rarely matters.) The theoretical (best possible) is determined by nose radius and feed (larger nose and lower feed gives a lower Ra). Rigidity: machine, fixation, tool, part... The weaker things are the more the pressure in the cut must be reduced. Depth of cut: There's a strong recommendation that at least 2/3 of the nose radius needs to be engaged, less then that and one is asking for problems. Insert geometry. A more positive insert will, especially in softer materials, give a better result ("sharper" and larger release angle). The more narrow the nose is (V vs D vs C...) the more we limit the point of contact which reduces cutting forces and increases release angles sideways. In real life what do we need to do? Reduce the nose radius of the cutter! This seems wrong but it allows for the rest of this list and the sum gives a finer result. Reduce feed. Reduce depth of cut (but be aware of that 2/3s rule). This is to reduce the cutting forces. Make sure everything is a rigid as possible - vibrations are your worst enemy. Use correct cutting data - The big manufacturers of carbide inserts have plenty of information - use it to your advantage but also consider your machine and setup, manufacturer's data is normally based on very stable conditions and high performance machines. EXPERIMENT, test! Learn to know your machine and materials. Are you using the right insert? Talk to your seller, any good supplier of tooling have support staff with deep knowledge to help their customers. And last but not least, handle your part with care! Even a slight "ting" might damage the surface and earn the label "REJECTED". So treat them like raw eggs. When I taught at a two year CNC extension program (students needed to be at CNC operator level to start) we did as much of tests like in this video we could. Testing things like this makes a difference. I've also worked with food, medical and gas turbines products and those are picky on surfaces. For those wanting to learn more I can warmly recommend Sandvik Coromant's E-learning. It's free and very well written and illustrated. (It's under "Knowledge & Services")
I was surprised that nose radius vs depth of cut had so little effect. I am using carbide inserts on a manual lathe but I am using old HSS surface speeds and get poor finishes. While I lack the rigidity of your CNC, it is a BX tool post on an 450Kg ENCO lathe . I will try something beyond the 100 SFM steel and 200 SFM Aluminum I use in the 4CS/D calculation. Thanks for the idea.
For 1" diameter = 3.1415" circumference. 12" (one foot) divided by 3.1415"= 3.8197 revolutions of the 1" bar to do 12". So 3.8197 times 800 = 3055.77 RPM for 800 surface footage. The equation is. SFM = RPM × D × (π ÷ 12). So for 800 SFM at 10,000 rpm the diameter would be .30557". So yes that is less than 1" diameter and probably a size you would be machining. But you would also not being using mild steel for your parts. So it would not be necessary to run at 800 SFM. But this is why commercial screw machines turn high RPM on their spindles. Thanks!
Wops! Seems like I messed up at converting imperial to metric. Nowadays I’m turning a 1040 steel part which has 16.5mm id and +0.015mm tolerance. I’m going to machine 15.000 parts. Turning tool recommends to work between 200-350 m/min. Which means rpm should be at least 3850 and my machines limit is 4000. I don’t know why but turning over 3000 rpm frightens me. That’s why I’m having trouble to have the surface finish I want. Thanks a lot!
my max bar is 1.25" so i dont like running the 800 sfm rpms. i can turn 5000 rpm but i dont like to mainly for the time it takes to slow down because i have a gantry style machine and do not have the time between tool changes, plus i run 2nd ops in it. i was told to run more than the tool radius and can run 300-400 sfm at .0025-.0035 ipr. with a .008r at .01-.015 doc. with that tip r .005 ipr is a roughing pass. imo you can run a lot deeper, even too deep, and way faster with that tool radius in this video. anyway, more videos to make that everyone would like to see, examples!! thanks for the video!
I was told that you should keep you DOC at half the insert radius at minimum. I dont any turning anymore really so i dont have much experience but that seemed to work well for me
Thanks Peter, I hope you will do one more test on this that answers this question. I am a hobby machinist dabbling in CNC. So, is the Material Removal Rate a better guide than either depth of cut, or surface speed since those are both in the MMR calculation?? As long as you are in some performance envelope the tool is ok with, maybe you can trade depth of cut for surface speed? And, If this works, when you hit a parameter you can't get around (such as max rpm for the machine, but too small of a diameter to achieve the surface speed) can you adjust something that isn't maxed out in order to recoup the good surface finish?? (In this example, going to a deeper doc at the max spindle speed to achieve the same MMR number) ... Thoughts? As I watch many CNC vids and work thru learning fusion, the MMR numbers seem to be dominating the tooling paths. Thanks for your efforts and love the education! Ordered a hobby cnc machine so paying attention...
Excellent series Peter, how about how would you go about getting a good finish on a small diameter part with a large machine like yours having limited rpm
In general I don’t turn small diameter parts out of mild steel on this machine. All my parts are more exotic materials. Put if I had to. I might have to get things the best I can. Then go to a machine where I could do some polishing.
On this big machine with this soft material probably not much. But on tougher material it would make a difference. That wasn't the intent of this demonstration. In a real job you would want the depth of cut after roughing to be constant. This is why your finish diameter can change from your roughing cycle changing. Say from a chipped or worn roughing insert. There are some commentators here saying they take the full tip radius or even deeper on the finish tool. Not to be critical of them if it works for them. But to me that's not really a finish pass. Its just more roughing. And then what if the part comes out oversize out of tolerance. They are going to have to rerun the tool. Now they are taking a small depth finish pass. Like I said in the video. That second rerunning of the finish tool is going to ruin their finish, if they don't speed up the surface speed. In this type of material.
Best results are usually achieved when the depth of cut exceeds the radius of the blade by 2 times so if you have a radius of 0.8mm, 1.6 of radial debth of cut will result in a smoother surface than below that.
Depth of cut is critical when it comes to surface finish. Depending on material, sometimes a .01 pass is good enough, other times a nice beefy .05 pass is perfect. I tend to use Spindle Speed Variation whenever possible and I always get the finish desired. If your machine has it, use it.
Sadly I am often times forced outside the manufacturers recommended speeds and feeds because my machines just can’t run that fast. Then have to resort to abrasive operations for final finish. The harder the material the less it’s a problem.
I'm commenting this without having watched the video, I also have training on machine tools but only a couple of weeks, so I wouldn't say I'm a machinist: When the depth of cut is too small the finish often came out terrible. Increasing the Doc a bit helped a lot. Especially as a beginner it felt comfortable to take it slow (last video) and a small Doc but that did not work well. Now to see what the video has to say.
On that very first cut, I don't see a difference from area to area, but I definitely see a difference from the very end compared to the shoulder you created.
It really confirms that the tool needs to be sufficiently loaded to cut consistently and cleanly. Whether proper loading is achieved trough depth, feed or speed seems to be negotiable but it needs to be sufficient, one way or the other. For very light finishing cuts, do you have any experience using cutters with a shearing geometry? I know they used to use those in the old days (manual / HS steel), esp. for gummy materials. But, in my admittedly very superficial experience, I've never seen a modern equivalent in person or a vendor catalog, and even less ever used one. For finishing in your machine, have you ever considered using something like a hand-held crankshaft polisher? The safety interlock prevents you from running the spindle at speed but you can still rotate the headstock at low speed, right?
No I can't rotate any of the spindles with the doors open. I can only jog the turning spindle with the C axis engaged with the hand wheel. There is also a very slow jog in turning mode (and you have to hold a button down all the time). I never use this. But I assume the purpose is if the machine is in low range it is difficult to turn the chuck by hand. So maybe to indicate something. I always use the C axis for this myself. The milling spindle can't be turned on at all. With the doors open. There could be a benefit to using HSS for certain things. Plastics for instance. There were a few companies that use to make HSS inserts. A long time ago I used some. I don't know if they any longer exist. The inserts I used in this video may not be the best. This example may be different with different tools. This is precisely why I don't often mention feeds and speeds in videos. There are to many variables to concider.
@@EdgePrecision And then there are cermat inserts for specifically getting finishes using low depth of cuts in soft gummy steels like 1018.... Ofcourse those need higher SF... But DoC can be kept low ..
Great research here. Looks like it wants a certain level of heat in the cut zone. Crappy finish when chips are silver and getting better as the chips turn gold to blue. If heat in the cut zone is the main factor then what effect does coolant have?
The coolant will have some effect, but not as much as you might think. Right at the cutting edge it still gets hot. The coolant really mostly cools the body of the insert and part. You can tell because the shavings still come off discolored even with coolant. maybe just a little less.
Thanks for the video. I've been watching machining content for years now and I wish somebody would give an intuitive explanation for *why* surface footage matters. Like, what is it about it surface footage that leads to different types of finishes? Is there an intuitive way to explain it? Thanks.
The answer is simple: Heat and material flow. Both higher SFM and feed rate generate more heat, and causes the material to shear/flow better, which gives you a better surface finish, up to a certain point.
@@kevind1865 Thank you. This was really helpful. Just to clarify, after a certain point, too much heat is detrimental to the insert/tooling and results in poorer finish? Also, would the principle you described indicate that sfm would be different whether or not you had coolant? I would assume that coolant would mean higher surface feed rates required to achieve the same surface finish, but allow quicker machining times. Am I understanding this correctly or is there something I'm missing? Again, thanks for your response.
@@danf6070 My question also. I think coolant might not have a big effect because the actual cut zone is still going to get up to temp before the coolant can reduce it. The cut zone itself is very hot over 700C, way above the boiling point of water or oil so it shouldn't be able to get all the way in. Still it will cool the material and the tool.
I think it does! If your lathe is doing max. like 1500 RPM and you have to finish a OD like 1", you be a little to slow at ordinary steel. Than you have to use a double or more cuttingdepth to get a clear surface.
Would be interesting to run this test on a piece of 12L14. I was maxing out my G50 anyway @ 2500 RPM. Still looked like crap until I went to around .03 doc.
I have good luck turning free-machining steels (12L14, 11L17, 1213, 4142 etc) with high rake, polished edge larger nose radius inserts that would generally be used with nonferrous metals. Leaded steels almost tear out like wood does, and with a negative rake tool they can smear pretty badly.
Heat can also be a factor. I've had parts give good finishes when they get hot but once i cool them down and take another cut at the same parameters the surface finish goes to crap. Certainly not a reliable technique cause of expansion and all that fun stuff just an interesting fact.
I think you are correct. But you can also say something the coolant is doing is the problem. One thing I learned doing this test is. Already people in these comments say things, but they just have their ideas but no real scientific profe. Just sort of guessing at what they feel works. And maybe in the past it did for them. This is precisely why I resist to give feed and speed data. Because everyone has their biases. Because of so many variables what works for me may not work elsewhere.
@@EdgePrecision coolant can help or hurt for sure depending on the situation. Regarding my example this was something i noticed while running manual lathes. Because i dont like a big mess I'll run dry through the roughing then cool the part down while i take a bathroom break or something and then I'll do the finish work dry as well. So aside from maybe some residual residue the coolant wouldn't be a factor.
In my experience you lose surface finish with carbide if your cut depth and feed rate/rev is less than the cutting edge radius of your tool as it burnishes rather than cutting. I don't mean tip radius, I mean cutting edge radius... Carbide inserts almost always have a rounded cutting edge for strength.
Only when I do unusual things the cam software wont handle easily. Something like a sub program for a broaching/shaping operation as an example. like when I squared up the hardy hole in the anvil.
One factor you did not include is the COOLING FLUID, does cooling fluid make a difference to surface finish - specially on deeper, high-RPM cuts, keeping the cutting edge cooler and preventing it from irregular thermal expansion which may throw some part of the cutting edge out of tolerance, causing irregular surface finish
Coolant will make a difference. For the video's sake I didn't use coolant. In this material coolant would probably make the finish worse, using carbide tools. It may make it better if using HSS tools. That could be a test worth doing.
@@EdgePrecision - Thermal expansion is a basic law of physics, all materials expand and contract with temperature. Cemented Tungsten Carbide has a low thermal expansion, but it will expand and change shape under elevated temps above 400 C, (depending on Nickel content), hence affecting surface finish. Here is a good research paper about the subject nvlpubs.nist.gov/nistpubs/jres/18/jresv18n1p47_A1b.pdf
I think you are correct. In the real world, when you have to hold close tolerances (say .001" or less). I don't think you would want to take a deep finish pass just hoping to hit your target point. Especially on expensive parts. So I generally sneak up on the dimension. This generally means taking a few very shallow finish passes. The purpose of this video was to show that proper surface speed is more important then dept of cut for a finish.
@@EdgePrecisionI'm from the metric site :) . I have to hold tolerances down to 0.006mm. How deep the finish cut is, depends on the tool nose radius. P.e. if I have a 0.8mm nose radius, I let 1.6mm left at the diamater for the finish cut. works perfect and is very stable - we have orders from 1 up to 1000 parts.
Because the very nature of milling is a intermittent cutting. So unlike turning (Except a intermittent cut in turning) there are different conditions for the tool.
Here's a cool video showing the shearing of steel at the cutting edge. You can see material go underneath the cutter around the 30 second mark. I can imagine this happening where the cutting parameters are less than ideal. Like your 400/.0025" example. th-cam.com/video/mRuSYQ5Npek/w-d-xo.html
What you see at 30 s is what is known as "build up edge". But do note that the video is filmed at microscopic levels with a sharp HSS tool which give quite different dynamics. So sad they haven't posted a scale. Build up edges leads to variations on depths of cuts and will after repeated cycles of break the edge of the cutter with unreliable and varying cuts as result. When working with carbide increase the cutting speed, change to another coating or to a more positive insert if this happens.
@@EdgePrecision What grade/breaker? I'm curious whether you're running into geometry issues anywhere during these tests, and what the Sumitomo's recommended feeds and speeds are for that insert.
I'm not sure I understand what's being done here. Roughing cut steps at .003" up to .030". So the stock diameter gets incrementally smaller towards the chuck. Finish cut steps at .003 up to .030. So the actual finish cut at any point is still .003". I have watched hundreds of these machining videos and it's my observation that small finishing cuts are nearly always worse than the roughing cuts, especially on non CNC machines where the surface speed doesn't change in relation to diameter. I often watch Adam Booth machining and the surface finish on many of the parts he makes deteriorates dramatically when he drops the finishing cut to just a few thou.
The steps get larger in diameter as the tool turns closer to the chuck. The finish pass is straight (No steps). So the depth of cut (On the finish cut) gets deeper by the increase in diameter of each step. So the intent of this video was to show for the same spindle speed (Surface speed). What happens to the finish when the depth of cut increases. Does that make more difference? Or does the surface speed make more difference in the finish? Or can you compensate for lower spindle speed by increasing the finish depth of cut, to improve the finish. I think it does show that if you can't go to a high enough surface speed for some reason, that increasing the depth of cut can help. But not as much as surface speed. In these softer materials. And it was also intended to show what a slow surface speed finish looks like.
@@EdgePrecision Thanks for clarifying that, I completely misunderstood the two cuts, both roughing and finishing. The results would seem to reinforce what I see on conventional lathes, as in the case of Adam Booth, where the higher depth of cut for the roughing tool gives a much better finish than the finish cuts. Although he does appear to change speed (spindle speed) at times when doing the finish cuts. Great channel by the way, I have been subscribed for some time now. As I spent many years in QA here in the UK working for Davall Gears, I would find it interesting to see your inspection setup and techniques.
In MY experience: 1) Proper depth of cut can prevent surface damage by wrapped up chips. Having a DOC that gets the chips to properly brake will minimize the risk of smeared/scratched surface finish. 2) Some materials will have perfectly fine surface finish with a wide range of DOC. Some materials tend to have better surface finish with a proper (deep enough) DOC. 3) Most of the time cutting a bit deeper then nose radius depth is deep enough. Sometimes for best finish 2x nose radius depth is needed. 4) Super shallow cuts with extremely high cutting speeds are almost always amazing finish.
I will add that tiny depth or cuts/spring passes can bump the tool off and on the cut due to the elastic deformation of the workpiece material underneath causing it give in (also softer materials will take more deformation until they "fail" into a chip, so they will most likely leave hangers and boogers if the doc/fr aren't enough to go past it), and won't produce the shiniest surface possible, even with the sharpest light/fine turning grades available.
With that said, on steel you can take a 0.01mm depth of cut with a really sharp, fine turning ground insert (even better the honed/lapped tolerance grade E), and even if it doesn't get scratched or bumpy, it will still not be as reflective (and probably a bit rougher along the cut) due to the reduced cross section of the chip, not conducting/spreading heat in the same way, as well as the minimal cutting pressure being inadequate to produce the work-hardened, compressive residual stress layer, that gives the machined material the shiny surface (due to the material under the shear zone being prestretched at it's yield point and not being able to take enough extra deformation to leave hanging crud) and some forged like qualities (that's why even stress relieved materials will warp when machined with cutting tools versus EDM etc)
Just a quick English lesson ....the word is BREAK .....not BRAKE.
Also, what you are completely missing is the word SHEAR ....which is what this is all about.
I also point out that nothing has been discussed about the insert .....NOTHING. You mention "2x nose radius depth is needed". This is very misleading and in some cases incorrect. The condition of the material is what will dictate what is needed.
Every hear of "Denitool"? Look it up ...and even better ...try this product. You WILL NEVER look at inserts the same way again.
.
I do production, and for chip control, and tool life, I always take right above tool radius, and with enough feed to ensure chip breakage(but of course stay within surface spec). I found that if I only take 0.2mm radial cut for a finishing pass with a R0.4 nose radius. After 20-50 parts, I'll start to see a flat spot on the insert radius(plastic deformation), leading to a faster deterioration of the surface quality. Meanwhile, if I take a 0.5-0.8mm radial doc, the insert will last me 200+ parts, without any nest building, or a big surface quality decrease.
I'm a total amateur and these types of examples help understand so much. Very glad you do these. Thanks for sharing, always!
Why didn't I think of doing an experiment like that years ago....very helpful. Low carbon steel is always a challenge to get a good finish, especially on a manual lathe. Hate when you take that last pass and the finish goes bad on you.
I wonder how many turners use the same tip for finishing that they have just roughed out a ton of metal and wonder why the fish is rough.
@@gangleweed I have a particular tool that leaves a very good finish in mild steel but it only works starting at 4mm diametral depth of cut. fun times when I need to turn a 20mm bar into 16mm + - 0.01mm in one single pass, at least I don't have to sand to get an acceptable finish.
@@user-tw9io9nz2m Here's a tip for you.....if you want to get a " chrome" plated finish on any mild steel try doing a finishing cut at .06mm deep and run the lathe at 60 rpm if you can go that slow and use coolant......the curl that comes off will be like ally foil......works for any other metal too.
I use a tool that looks like a parting tool but has a 6mm wide tip face, honed sharp......keep the tool face dead square to the work piece and you can use a fairly fast feed to save time.
Using that method I've formed large radii with a form tool on my old capstan lathe many years ago.
@@gangleweed I’ll have to try that out, my lathe goes down to 40 rpm. Don’t have flood coolant setup yet but I could use some in a bottle.
@@user-tw9io9nz2m Yep, I can guarantee that if you take a shallow finishing cut using a slow speed with a broad tool the finish will be like chrome plate.
If the tool is shaped like a parting tool and honed sharp......6mm wide is good........it peels off a sliver like fine foil......the feed rate can be quite coarse as the finish is determined by the tool width, but it must be dead square AND DEAD ON CENTERE to the work piece or you'll get cyclic grooves as it cuts........using it on brass is awesome.......as long as the work piece is kept lubed with coolant the finish will be shiny.
Thank you for taking a methodical approach to this and for sharing your results; there's no end of permutations but having an idea of where to start helps a lot.
As an apprentice school tutor.
Using your content in my classes, YOU ARE MAKING A DIFFERENCE PETER..
thank you Sir.
"But what about depth of cut?" That was the question after watching your last video. Thanks for that. Good practices for preparing for jobs in different materials using different tools.. Excellent video.
I like how you made each pass become 10 separate tests with the varying depths, rather than doing them one at a time. Very clever. I'll have to remember that one for sure. Maybe a may not remember the results here --- but I'll remember how to run the test and get my own results next time. Great stuff
Great video you open my eyes up and you have learned through your experiences and it’s great that you’re sharing them because I’m going to look at things a little differently
Well done Peter. Fantastic demonstration.
Cool presentation!
Thanks!
Appreciate you sharing your time with us.
Fascinating, it’s one thing to read about stuff like this but thanks for demonstrating it
Thank you Peter!
The main factor for a good finish, if we are talking about steel - like in your video, is cutting zone temperature.
Which your tests showed very well.
Everything that increases that (to a certain point) will increase it, since the chip will shear much cleaner from the material.
Coolant won't make a large difference or only at very low SFM.
A used insert (not broken) will almost always make a better finish than a new one, since isn't as sharp and creates more temperature.
That goes for everything that increases it, like: "dull" tool geometry (thats why its always shiny after roughing) , higher SFM, higher DOC, higher feed, tougher material etc.
Of course every grade of steel is different and requires certain parameters.
But generally something like 1018 will only finish good at roughing cuts or very high SFM, while 4140 won't be much trouble to get a good finish.
(but again, the toughness creates way more temperature, so it helps a lot by itself)
I can add a reference book to the discussion. I am a hobbyist, and have only read a little bit of this book.
"Metal Cutting Principles", second edition, by Milton C. Shaw, copyright 2005, Oxford University Press
Excellent experiment.
I agree with you. Built up Edge happens because of cutting zone temperature being too low. From what I've seen of materials under the microscope, the poor surface finishes seem indicative of material smearing.
My only disagreement is on "coolant" (I highly prefer the term cutting fluid). Generaly cutting fluid reduces friction from the chip with the cutting face (the hottest zone) so in effect tool heat, while still allowing to maintain enough heat in the shearing zone.
In my experience cutting fluid (even a measly oil mist) makes a big difference in reflectivity, even with cutting speeds well above the shiny zone (with no stuck built up edge, no hangers from the material elastically deforming more than the doc/fr, no chewed up finish from chips bumping back on the workpiece), it will still increase the reflectivity of the surface by preventing rapid oxidation of the material under the cut from getting exposed to air at high temperatures.
Also it's the only way to get a completely smooth, mirror finish on mild steel when milling... without cutting fluid it just goes from a dull grey to having burn marks if you keep pushing the speed but it will never look shiny and crisp without it (width of cut won't do much either)
@@Sketch1994 usually turning (or all operations with continues tool engagement) always are done with coolant or cutting fluid.
Of course it helps in the long run and will improve the finish, but not to a level where too low SFM or other bad paramters are compensated.
Regarding milling on mild steel:
We do most of our milling dry. (10 to 20x more toollife compared to high pressure TSC) Exceptions for side finishing, thread milling, deburring and form tools.
Mostly 1018 and 1045.
Best way to get got surfaces is just to use an insert with a long wiper edge and running at least 650 SFM.
Seco Square 6 shoulder mills work extremely well, or double Octomill with M11 geometry. (all dry aswell)
To get almost mirror like finishes, try Cermet tooling with around 1000 SFM.
But spindle alignment etc. need to be spot on.
Thank you so much for this superb follow-up video - it answered many of the remaining questions I had at the end of the first video. I now I have something definitive to attempt to replicate on my (slightly worn out) HLV-H - or at least understand if I’ve reached the limit of what’s possible without a rebuild.
Thanks!
Sooo good, thank you Peter, It help with the project on hand.
Very, very helpful, thank you.
What a great demo, I’d like to say I’d show this to some on the younger lads at work but to be honest most of them aren’t interested in learning on my opinion. However i definitely enjoyed it.
This information is great. Great comparisons and that can be referenced!
buen video peter..gracias por tu tiempo
VERY useful information thanks.
Very cool tests.. I learned a lot. It answers so many "what if" questions. I see why you are saying SF instead of spindle RPM; because depending on the diameter of the work, the SF changes a lot, at the same given RPM. It's crazy to see so many variables in such a simple and straight forward test; and we haven't even talked about different tooling HSS vs carbide- or even all the variables of turning different materials, such as HC steel vs copper vs brass vs stainless vs aluminum, etc... I feel like I know just enough to realize there are so many things that I don't know. lol.
You also forgot to mention machines and the difference in setups. This is one of the reasons I don't often mention speeds and feeds in my videos. There are so many variables that what I do probably wont work for you the same. What I want to encourage with these type of videos Is. People should make tests with their own equipment, tooling and setup to get the correct cutting conditions. That said this might give some idea where to start.
@@EdgePrecision ....also completely missing is MEASURED RESULTS .....rather than just talking and saying "this looks really good".
.
When wall thickness is less that time so meny problems came , but stock also playing an important role while finishing. Thanks for sharing
Love the content! - really interesting to see the different finishes!
Sure there is a recommended depth, Cutting speed and feed for every insert - but these comparisons really help when your machine is not capable of a high enough surface speed or a fast feed.
Could get you out of a tight spot when chasing some tough drawing specs.
Thank you for this :)
Might be a good idea to include pictures from your Phone in the Video to help visualize the surface - the gopro isn't too happy with this close focus.
Greetings from Germany
very useful. thanks.
Thanks Peter! Really notice the DoC effect at these feeds. Your machine looks like it wants aggressive cuts with light cuts and faster feeds for finishes, and the 800 feed does work well.
its so helpful to me. thanks
Great video Peter. I wonder how many people read the back of their insert packets. Things really go better when you follow the manufacturers recommends surface speed and depth of cut.
Really interesting and well executed test! Makes me wonder if the inertia of the material coming off has something to do with the quality of the finish, and what the graph would look like if we could plot surface finish against say the mass flow rate off the part at various surface speeds.
Great video does appear to be 1018 i began running a okuma in 1988 and have always left 0.01 on dia 0.002 on faces tor most materials i do increase finish depth for smaller diameters if i max rpm is reach
wonderful
nice subject. thanks
Cermet inserts also work great for steel. Mitsubishi MP3025. They also have a wiper geometry so you can feed double the feed and achieve same surface finish .
Very interesting, thank you. My little lathe can't hit those speeds. I have found that running coolant makes a marked difference to the finish I can achieve.
Great information. Inset sharpness has a big effect when taking whisper cuts on my little Super 11. I hand lapped an insert to make it very sharp and finish on a whisper cut was much better but they don't stay sharp long. Maybe diamond tooling would hold and edge longer.... JMHO....
Came to similar conclusions on cut conditions despite using different metrological system. Thanks for sharing!) Very helpfull and informative!)
Like I said in the video. I have never done this test before. I had to think of a way in a video how to demonstrate it. This is what I came up with. I pretty much knew what would happen from experience. It did pretty much what I expected. Thanks!
Nice video Peter
This and your surface speed video are great! Years doing this and I've never run a test like this. Its so great to see it side by side in a controlled way. Do you have any plans to continue with similar testing for us? Im trying to think of other things of interest...tool life is probably too tedious to test scientifically, maybe chip control, different insert grades or chipbreaker geometries, milling tool paths - old school slotting vs adaptive / trochoidal....not sure if there is enough meat there to make a full video, just throwing out some ideas in hopes of seeing more testing :-D
Most interesting! Thanks!
I'm wondering if coolant or cutting oil has any effect on surface finish. Might be interesting to rerun one of the ones that showed variation (maybe 400/.005, I think was one) with coolant and see if the result is the same.
Would be interesting to see a test with a profilometer on one of those pieces with a visible difference in surface finish on each step. Does a better looking finish mean a better measured finish?
In short: No.
Our eyes tend to prefer shiny while measurements are based on the actual surface profile.
That said an experienced person can often judge if a surface is "good" or not. But it doesn't replace a measurement. And there are also multiple ways to measure that can't be compared to each other (Ra, , Rq, Rt, Rmr...)
It doesn't, it can look good to our eye and be awful when actually measured.
We as humans tend to think that shiny and homogeneous looking equates to a good finish but that can be misleading.
Guys that have been doing this for a few decades though can usually eyeball what kind of finish it is and in my experience be correct about it most of the time once it has been actually measured.
Nice test Peter.
I've always held to the idea that minimum depth of cut should match the nose radius of your finishing tool. I prefer to double it and crank the surface footage up. My standard finisher has a .4mm nose radius, so I typically write programs with a U-.032 and G96 S1500. The shop I work for strictly runs haas machines. That machine can handle so much more, especially with a .032 nose radius. A cut at .062 deep at 600-800 sfm (I'd max the spindle out if I were running it) would shine like a diamond.
I also just happen to love the sound of chips spraying the door. It's the sound of my people.
wouldn't it be U-.064?
Nice I use an .008 thou rad finish at 656sfm and .0036 feed around .005 doc . I did tests just like your doing within the manufacturer’s recommended speeds. I would love to have one of the integrex machines. maybe one day…
We've started doing deeper finising cuts to reduce the chip stringing, if the setup can take it we do 1/8th inch off the diameter for a finishing cut with a 1/32nd nose radius insert. Perhaps going deeper could help you as well.
A couple of important points to add along with the video (in no particular order and with way to brief explanations):
(Post updated with geometry below)
It is very important to differentiate between visual and measured finish - Look at what the customer specified! (Most common is measured in Ra, if it "looks" shiny or not rarely matters.)
The theoretical (best possible) is determined by nose radius and feed (larger nose and lower feed gives a lower Ra).
Rigidity: machine, fixation, tool, part... The weaker things are the more the pressure in the cut must be reduced.
Depth of cut: There's a strong recommendation that at least 2/3 of the nose radius needs to be engaged, less then that and one is asking for problems.
Insert geometry. A more positive insert will, especially in softer materials, give a better result ("sharper" and larger release angle). The more narrow the nose is (V vs D vs C...) the more we limit the point of contact which reduces cutting forces and increases release angles sideways.
In real life what do we need to do?
Reduce the nose radius of the cutter! This seems wrong but it allows for the rest of this list and the sum gives a finer result.
Reduce feed.
Reduce depth of cut (but be aware of that 2/3s rule). This is to reduce the cutting forces.
Make sure everything is a rigid as possible - vibrations are your worst enemy.
Use correct cutting data - The big manufacturers of carbide inserts have plenty of information - use it to your advantage but also consider your machine and setup, manufacturer's data is normally based on very stable conditions and high performance machines.
EXPERIMENT, test! Learn to know your machine and materials.
Are you using the right insert? Talk to your seller, any good supplier of tooling have support staff with deep knowledge to help their customers.
And last but not least, handle your part with care! Even a slight "ting" might damage the surface and earn the label "REJECTED". So treat them like raw eggs.
When I taught at a two year CNC extension program (students needed to be at CNC operator level to start) we did as much of tests like in this video we could. Testing things like this makes a difference. I've also worked with food, medical and gas turbines products and those are picky on surfaces.
For those wanting to learn more I can warmly recommend Sandvik Coromant's E-learning. It's free and very well written and illustrated.
(It's under "Knowledge & Services")
Cool - thanks!
I was surprised that nose radius vs depth of cut had so little effect. I am using carbide inserts on a manual lathe but I am using old HSS surface speeds and get poor finishes. While I lack the rigidity of your CNC, it is a BX tool post on an 450Kg ENCO lathe . I will try something beyond the 100 SFM steel and 200 SFM Aluminum I use in the 4CS/D calculation. Thanks for the idea.
As a small arms parts manufacturer, having nice surface finish is really challenging. 800 sfm requires over 10k rpm for parts under 1” diameter.
For 1" diameter = 3.1415" circumference. 12" (one foot) divided by 3.1415"= 3.8197 revolutions of the 1" bar to do 12". So 3.8197 times 800 = 3055.77 RPM for 800 surface footage. The equation is. SFM = RPM × D × (π ÷ 12). So for 800 SFM at 10,000 rpm the diameter would be .30557". So yes that is less than 1" diameter and probably a size you would be machining. But you would also not being using mild steel for your parts. So it would not be necessary to run at 800 SFM. But this is why commercial screw machines turn high RPM on their spindles. Thanks!
Wops! Seems like I messed up at converting imperial to metric. Nowadays I’m turning a 1040 steel part which has 16.5mm id and +0.015mm tolerance. I’m going to machine 15.000 parts. Turning tool recommends to work between 200-350 m/min. Which means rpm should be at least 3850 and my machines limit is 4000. I don’t know why but turning over 3000 rpm frightens me. That’s why I’m having trouble to have the surface finish I want. Thanks a lot!
my max bar is 1.25" so i dont like running the 800 sfm rpms. i can turn 5000 rpm but i dont like to mainly for the time it takes to slow down because i have a gantry style machine and do not have the time between tool changes, plus i run 2nd ops in it.
i was told to run more than the tool radius and can run 300-400 sfm at .0025-.0035 ipr. with a .008r at .01-.015 doc.
with that tip r .005 ipr is a roughing pass.
imo you can run a lot deeper, even too deep, and way faster with that tool radius in this video.
anyway, more videos to make that everyone would like to see, examples!!
thanks for the video!
I was told that you should keep you DOC at half the insert radius at minimum. I dont any turning anymore really so i dont have much experience but that seemed to work well for me
Never actually done a test like this, but with experience you learn that this is exactly what would happen.
Thanks Peter, I hope you will do one more test on this that answers this question. I am a hobby machinist dabbling in CNC. So, is the Material Removal Rate a better guide than either depth of cut, or surface speed since those are both in the MMR calculation?? As long as you are in some performance envelope the tool is ok with, maybe you can trade depth of cut for surface speed? And, If this works, when you hit a parameter you can't get around (such as max rpm for the machine, but too small of a diameter to achieve the surface speed) can you adjust something that isn't maxed out in order to recoup the good surface finish?? (In this example, going to a deeper doc at the max spindle speed to achieve the same MMR number) ... Thoughts? As I watch many CNC vids and work thru learning fusion, the MMR numbers seem to be dominating the tooling paths. Thanks for your efforts and love the education! Ordered a hobby cnc machine so paying attention...
i would say the depth of cut in low/mid carbon steel is really important to get a shiny finish. the feed too
Material?
In my experience a36 vs 4340 vs 4340 prehard will vary the finish a lot.
Excellent series Peter, how about how would you go about getting a good finish on a small diameter part with a large machine like yours having limited rpm
In general I don’t turn small diameter parts out of mild steel on this machine. All my parts are more exotic materials. Put if I had to. I might have to get things the best I can. Then go to a machine where I could do some polishing.
Would be interesting to see how the different depths affect the size after you mic it at the different steps
On this big machine with this soft material probably not much. But on tougher material it would make a difference. That wasn't the intent of this demonstration. In a real job you would want the depth of cut after roughing to be constant. This is why your finish diameter can change from your roughing cycle changing. Say from a chipped or worn roughing insert. There are some commentators here saying they take the full tip radius or even deeper on the finish tool. Not to be critical of them if it works for them. But to me that's not really a finish pass. Its just more roughing. And then what if the part comes out oversize out of tolerance. They are going to have to rerun the tool. Now they are taking a small depth finish pass. Like I said in the video. That second rerunning of the finish tool is going to ruin their finish, if they don't speed up the surface speed. In this type of material.
Best results are usually achieved when the depth of cut exceeds the radius of the blade by 2 times so if you have a radius of 0.8mm, 1.6 of radial debth of cut will result in a smoother surface than below that.
Very useful, thanks. Even if it is all in freedom units 🙄(😏)
I have heard of "burnishing tools", are these used to improve surface finish? Do you use them?
Depth of cut is critical when it comes to surface finish. Depending on material, sometimes a .01 pass is good enough, other times a nice beefy .05 pass is perfect. I tend to use Spindle Speed Variation whenever possible and I always get the finish desired. If your machine has it, use it.
Sadly I am often times forced outside the manufacturers recommended speeds and feeds because my machines just can’t run that fast. Then have to resort to abrasive operations for final finish. The harder the material the less it’s a problem.
I'm commenting this without having watched the video, I also have training on machine tools but only a couple of weeks, so I wouldn't say I'm a machinist:
When the depth of cut is too small the finish often came out terrible. Increasing the Doc a bit helped a lot.
Especially as a beginner it felt comfortable to take it slow (last video) and a small Doc but that did not work well.
Now to see what the video has to say.
On that very first cut, I don't see a difference from area to area, but I definitely see a difference from the very end compared to the shoulder you created.
It really confirms that the tool needs to be sufficiently loaded to cut consistently and cleanly. Whether proper loading is achieved trough depth, feed or speed seems to be negotiable but it needs to be sufficient, one way or the other.
For very light finishing cuts, do you have any experience using cutters with a shearing geometry? I know they used to use those in the old days (manual / HS steel), esp. for gummy materials. But, in my admittedly very superficial experience, I've never seen a modern equivalent in person or a vendor catalog, and even less ever used one.
For finishing in your machine, have you ever considered using something like a hand-held crankshaft polisher? The safety interlock prevents you from running the spindle at speed but you can still rotate the headstock at low speed, right?
No I can't rotate any of the spindles with the doors open. I can only jog the turning spindle with the C axis engaged with the hand wheel. There is also a very slow jog in turning mode (and you have to hold a button down all the time). I never use this. But I assume the purpose is if the machine is in low range it is difficult to turn the chuck by hand. So maybe to indicate something. I always use the C axis for this myself. The milling spindle can't be turned on at all. With the doors open. There could be a benefit to using HSS for certain things. Plastics for instance. There were a few companies that use to make HSS inserts. A long time ago I used some. I don't know if they any longer exist. The inserts I used in this video may not be the best. This example may be different with different tools. This is precisely why I don't often mention feeds and speeds in videos. There are to many variables to concider.
@@EdgePrecision And then there are cermat inserts for specifically getting finishes using low depth of cuts in soft gummy steels like 1018.... Ofcourse those need higher SF... But DoC can be kept low ..
Great research here. Looks like it wants a certain level of heat in the cut zone. Crappy finish when chips are silver and getting better as the chips turn gold to blue. If heat in the cut zone is the main factor then what effect does coolant have?
The coolant will have some effect, but not as much as you might think. Right at the cutting edge it still gets hot. The coolant really mostly cools the body of the insert and part. You can tell because the shavings still come off discolored even with coolant. maybe just a little less.
Thanks for the video. I've been watching machining content for years now and I wish somebody would give an intuitive explanation for *why* surface footage matters. Like, what is it about it surface footage that leads to different types of finishes? Is there an intuitive way to explain it? Thanks.
The answer is simple: Heat and material flow. Both higher SFM and feed rate generate more heat, and causes the material to shear/flow better, which gives you a better surface finish, up to a certain point.
@@kevind1865 Thank you. This was really helpful. Just to clarify, after a certain point, too much heat is detrimental to the insert/tooling and results in poorer finish? Also, would the principle you described indicate that sfm would be different whether or not you had coolant? I would assume that coolant would mean higher surface feed rates required to achieve the same surface finish, but allow quicker machining times. Am I understanding this correctly or is there something I'm missing? Again, thanks for your response.
@@danf6070 My question also. I think coolant might not have a big effect because the actual cut zone is still going to get up to temp before the coolant can reduce it. The cut zone itself is very hot over 700C, way above the boiling point of water or oil so it shouldn't be able to get all the way in. Still it will cool the material and the tool.
I think it does! If your lathe is doing max. like 1500 RPM and you have to finish a OD like 1", you be a little to slow at ordinary steel. Than you have to use a double or more cuttingdepth to get a clear surface.
Would be interesting to run this test on a piece of 12L14. I was maxing out my G50 anyway @ 2500 RPM. Still looked like crap until I went to around .03 doc.
I have good luck turning free-machining steels (12L14, 11L17, 1213, 4142 etc) with high rake, polished edge larger nose radius inserts that would generally be used with nonferrous metals. Leaded steels almost tear out like wood does, and with a negative rake tool they can smear pretty badly.
12L14 is a leaded steel and I use HSS to finish a piece.....it depends on the job and production rate of course.
@@forrestcarroll9350 I think that’s what I did as well, used an Iscar CCGT high rake polished uncoated.
Heat can also be a factor. I've had parts give good finishes when they get hot but once i cool them down and take another cut at the same parameters the surface finish goes to crap. Certainly not a reliable technique cause of expansion and all that fun stuff just an interesting fact.
I think you are correct. But you can also say something the coolant is doing is the problem. One thing I learned doing this test is. Already people in these comments say things, but they just have their ideas but no real scientific profe. Just sort of guessing at what they feel works. And maybe in the past it did for them. This is precisely why I resist to give feed and speed data. Because everyone has their biases. Because of so many variables what works for me may not work elsewhere.
@@EdgePrecision coolant can help or hurt for sure depending on the situation. Regarding my example this was something i noticed while running manual lathes. Because i dont like a big mess I'll run dry through the roughing then cool the part down while i take a bathroom break or something and then I'll do the finish work dry as well. So aside from maybe some residual residue the coolant wouldn't be a factor.
In my experience you lose surface finish with carbide if your cut depth and feed rate/rev is less than the cutting edge radius of your tool as it burnishes rather than cutting.
I don't mean tip radius, I mean cutting edge radius... Carbide inserts almost always have a rounded cutting edge for strength.
softer steels often need large depth on finish passes .. or it will look bad
What is the nose radius on the finish tool please Peter?
30 thousands nose rad - sorry i missed that
Do you ever program g and m code by hand?
Only when I do unusual things the cam software wont handle easily. Something like a sub program for a broaching/shaping operation as an example. like when I squared up the hardy hole in the anvil.
One factor you did not include is the COOLING FLUID, does cooling fluid make a difference to surface finish - specially on deeper, high-RPM cuts, keeping the cutting edge cooler and preventing it from irregular thermal expansion which may throw some part of the cutting edge out of tolerance, causing irregular surface finish
Coolant will make a difference. For the video's sake I didn't use coolant. In this material coolant would probably make the finish worse, using carbide tools. It may make it better if using HSS tools. That could be a test worth doing.
@@EdgePrecision - Thermal expansion is a basic law of physics, all materials expand and contract with temperature. Cemented Tungsten Carbide has a low thermal expansion, but it will expand and change shape under elevated temps above 400 C, (depending on Nickel content), hence affecting surface finish. Here is a good research paper about the subject
nvlpubs.nist.gov/nistpubs/jres/18/jresv18n1p47_A1b.pdf
Hiya Peter
On much smaller diameters, when you run out of spindle speed, the finish will be much better with deeper finish cut.
I think you are correct. In the real world, when you have to hold close tolerances (say .001" or less). I don't think you would want to take a deep finish pass just hoping to hit your target point. Especially on expensive parts. So I generally sneak up on the dimension. This generally means taking a few very shallow finish passes. The purpose of this video was to show that proper surface speed is more important then dept of cut for a finish.
@@EdgePrecisionI'm from the metric site :) . I have to hold tolerances down to 0.006mm.
How deep the finish cut is, depends on the tool nose radius. P.e. if I have a 0.8mm nose radius, I let 1.6mm left at the diamater for the finish cut. works perfect and is very stable - we have orders from 1 up to 1000 parts.
testing laterally comparatively, you should use a center for support. Interesting video thanks!~
So you leave 0.010-0.015 for finish on turning what about milling? Same amount?
Milling is not that sensitive altough i'd like to hear why .
No milling is a totally different thing.
@@EdgePrecision Why is milling so different? will you please do something about finish allowance and trial cuts in milling? Thank you for your time.
Because the very nature of milling is a intermittent cutting. So unlike turning (Except a intermittent cut in turning) there are different conditions for the tool.
Here's a cool video showing the shearing of steel at the cutting edge. You can see material go underneath the cutter around the 30 second mark. I can imagine this happening where the cutting parameters are less than ideal. Like your 400/.0025" example. th-cam.com/video/mRuSYQ5Npek/w-d-xo.html
What you see at 30 s is what is known as "build up edge".
But do note that the video is filmed at microscopic levels with a sharp HSS tool which give quite different dynamics.
So sad they haven't posted a scale.
Build up edges leads to variations on depths of cuts and will after repeated cycles of break the edge of the cutter with unreliable and varying cuts as result. When working with carbide increase the cutting speed, change to another coating or to a more positive insert if this happens.
So I can try this on my south bend clone right? Lololololol nice vid thank you
This principal should apply to any turning. CNC or manual.
what brand inserts are you using?
In this video I’m using Sumitomo inserts.
@@EdgePrecision Do they have a good roughing insert for stainless that you would recommend?
@@EdgePrecision What grade/breaker? I'm curious whether you're running into geometry issues anywhere during these tests, and what the Sumitomo's recommended feeds and speeds are for that insert.
@@GeneralChangFromDanang Mitsubishi Materials US735 grade or MC7025 great for stainless
@@danno0505 I'll check it out, thanks.
I'm not sure I understand what's being done here. Roughing cut steps at .003" up to .030". So the stock diameter gets incrementally smaller towards the chuck.
Finish cut steps at .003 up to .030. So the actual finish cut at any point is still .003".
I have watched hundreds of these machining videos and it's my observation that small finishing cuts are nearly always worse than the roughing cuts, especially on non CNC machines where the surface speed doesn't change in relation to diameter.
I often watch Adam Booth machining and the surface finish on many of the parts he makes deteriorates dramatically when he drops the finishing cut to just a few thou.
The steps get larger in diameter as the tool turns closer to the chuck. The finish pass is straight (No steps). So the depth of cut (On the finish cut) gets deeper by the increase in diameter of each step. So the intent of this video was to show for the same spindle speed (Surface speed). What happens to the finish when the depth of cut increases. Does that make more difference? Or does the surface speed make more difference in the finish? Or can you compensate for lower spindle speed by increasing the finish depth of cut, to improve the finish. I think it does show that if you can't go to a high enough surface speed for some reason, that increasing the depth of cut can help. But not as much as surface speed. In these softer materials. And it was also intended to show what a slow surface speed finish looks like.
@@EdgePrecision Thanks for clarifying that, I completely misunderstood the two cuts, both roughing and finishing. The results would seem to reinforce what I see on conventional lathes, as in the case of Adam Booth, where the higher depth of cut for the roughing tool gives a much better finish than the finish cuts. Although he does appear to change speed (spindle speed) at times when doing the finish cuts.
Great channel by the way, I have been subscribed for some time now. As I spent many years in QA here in the UK working for Davall Gears, I would find it interesting to see your inspection setup and techniques.
does a bear shit in the woods?
Yes
There's probably some sort of harmonic phenomenon happening, I believe everyone usually calls it chatter, but at these small scales you can't hear it.