why do we set the compound rest at 29
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- เผยแพร่เมื่อ 26 ส.ค. 2024
- why do we set the compound rest at 29
In this video I will demonstrate and show you the different methods of setting your compound rest for different types of threading
I will also show you the result of incorrectly setting your compound rest
in general we do not set our compound rest to 0 there are special circumstances and other styles of threads that you need to set your compound rest to 0 an example of that would be setting up to do multiple start threads
I have been a machinist for 11 years, and thus is the best explanation of why 29⁰. I'll admit, i infeed at 0⁰ because I dont want to mess up my tool offsets on my DRO. Thanks for the video. Short and simple.
Thank you for the nice comment and thank you for taking the time to comment. It is much appreciated.
Ray
I'm the same. But I do have a trick to take load off one side insert and make nice thread. I simply drop out forward reverse lever and rotate chuck backwards a wee bit and drop forward reverse lever into next tooth. It advances leadscrew a fraction and you then only cut on one side. You get pretty fast at it and it doesn't mess with offsets on dro.
I was wondering why he was cutting at 29 degrees at all
The best part about TH-cam.
People who are prepared to share Information.
Your Information is correct.
But, rarely do I cut threads on a Manual Lathe with the Compound set to any other angle besides 90 degrees.
It's not to say that this is the way to do it ??
But, it works very well when you're Not using High Speed Steel to cut Threads ??
It's not to argue the point.
Just what works for me.
I cut all types of Threads on a Manual Lathe from Metric Fine, ACME to 4.5 tpi UNC.
All cut at 90 Degrees.
I back this up with videos showing the process.
Not trying oversell myself.
Just sharing information that works for me 👍
Thank you for sharing. It is much appreciated. You are correct you can leave your compound rest set to 90. Not a problem. I was just trying to explain the theory for my common core students or level one apprenticeship.
If you reply to this you should drop a link to your videos, the more shared content, the better
Ray
@@shopandmath Thanks for your reply, Ray 👍
I always look at the comments section as a Forum rather than somewhere to argue the point with someone who has used their own time to share information.
( unfortunately not a common thing to happen on Anti Social Media ??? )
I'm fairly new to your channel and I must admit it was something that I found interesting to watch.
I had to laugh a little to myself as I was writing my reply ??
I still remember having the exact same conversation with my teacher.
( a fair few years ago now, lol )
In 1 of the test we were required to take as part of our lessons.
This question came up on the test ??
I couldn't help myself to give the answer I want to give rather than the answer he wanted ??
Of course I wrote 90 Degrees, LOL.
The teacher gave back my test with a score of 98% ??
I asked Why 98% not 99% ??
His answer was. 1% for giving the incorrect answer.
And another 1% for being a smartass 😅
As I was leaving the classroom he said to me.
I wouldn't have given you a score of 100% because no gets a score of 100%
I asked, why's that ?
Because, giving you a score of 99% makes you think about why you didn't get 100%
😅Very Good 👌
Thanks for your offer to include a link to my videos.
But, I have already included too much information in my reply 🙂👍
I do the same only go half the depth of cut of cross slide on compound slide during roughing then very light finishing on both flanks at the end.
Joe pie did a very good video on this.
He explains and shows real time why when you are cutting 90° it's just fine.
Been a machinist for over 50 yrs. Never turned the compound to cut a thread. Fed the tool straight in and advanced the compound .005” or so each pass. Produced a fine looking thread on all pitches and materials.
Yes, that method will work as well
Out of curiosity, you’re not from New Zealand or Australia, are you
That is a technique that they teach in those regions as well
@@shopandmath from Canada. They taught the 29 deg method in first year. Went to work in a shop where we were paid piece work. The first time I went to turn the compound the head machinist came over and told me” they taught you how to make threads but my job is to show you how to make money and you are wasting time”.
Great explanation.
I notice that a guy in Australia who does you tube videos does not set his compound to 29 degrees but shifts it sideways a bit each pass.
That is Kurtis of Cutting Edge Engineering.
He has the compound at 90 degrees.
He feeds in x on the cross slide (at right angle to the spindle axis) and x/2 on the compound (parallel to the spindle axis).
So his cutting tool advanced 30 degrees to the right angle from the spindle axis.
Sin(30°) = 1/2
The technique will work, but it’s not one that I use during instruction for people that are new to the trade
I have been doing this for a long time, and I still learn new techniques and tricks from watching TH-cam videos. Thank you for taking the time to comment. It is much appreciated.
Ray
@@shopandmath Aint that the truth, never stop learning!!
It must be common way to do it here in OZ because I'm one of them.😊
@@mehmettemel8725 I worked as a machinist for 15 years including apprenticeship here in Oz, never seen a compound angled for thread cutting outside trade school besides an apprentice that we quickly educated, I don't even know why the bother teaching it, I've never seen anyone cut an internal thread with compound angled.
👍 excellent explanation! My old shop teacher taught us to take the last few thou off by feeding straight in to let the tool final form the thread.
Hi James
Thanks for the nice comment and thank you for taking the time to comment. It’s much appreciated.
I just did 1/2 -13 with cheap threading insert at 0°... fed in total of 0.116 on cross slide
came out perfect ...also tried from left to right with insert upside down at higher speed again turned out great love working out in the shop when its to cold to fish
I feed in with my cross slide when threading. However I still set the compound to 29 degrees so I can shift the cutter if I need to tweak the thread a bit. Still enjoying your videos!
Ive been a machinist for 25+ years and i cut threads using 29 degrees method and using the parallel method.
Both produce the same thread without any problems or difference.
The only difference is that when cutting threads by the parallel method you need to move the compound slightly for every infeed / pass you make.
The exact amount you have to move the compound is given in charts that are specific for parallel thread cutting.
I also noticed that in Europe most machinists learn the parallel method and usa machinists learn the angle method.
For the end result it doesn't make a difference , it's more what method you like to use and find convenient 😀.
I can use both methods and I will end up with exactly the same result .
Yes, both methods work
I made this video for my common core students or level one apprenticeship to highlight the difference between the two methods
If you’re using carbide inserts, either method generally produces the same results the differences is when you’re using high-speed steel
I do understand it industry. Nobody uses high-speed steel anymore, and I will also agree with most people who say threads are generally cut on a CNC.
We use the parallel method in level three apprenticeship for general machinist to cut multiple threads
Our common core general machinist class the first 2 threads that they cut need to be cut using high-speed steel, and after that they can use the carbide insert tools
Thank you for sharing. It is much appreciated and thank you for taking the time to comment.
Ray
I just use 0 deg. on manual as well CNC, no problems. As you go deeper take smaller cuts and always use sharp tools.
Hello, I really like your channel. I have been machining for quite sometime now and I am always up for learning something new and YOUR channel does exactly that. Cheers.
Wylie
Hi Wylie
Thank you for the nice comments and thank you for taking the time to comment. It is much appreciated.
Ray
You answered a bunch of questions, well done video, I've never done any threading before, but know I know how.
Thank you for the nice comment and thank you for taking the time to comment. It is much appreciated.
Ray
Wow, it makes sense if the compound angle is set improperly that the thread form would be incorrect but I've never seen it so obviously before. Wonderful example.
But I stopped using compound in-feed on manual machines that kick out the leadscrew engagement with carriage stops like the Hardinge HLV-H and Monarch EE. Losing absolute tool position and potentially gouging into a shoulder didn't seem like it was worth the additional setup planning/foresight. With modern carbide tooling, basically all common materials are 'easy' to finish just with plunging but I still do end up using compound infeed with superalloys and exotic stuff.
Great video and thank you for making this accessible!
Thank you for sharing it is extremely important to have other peoples experiences expressed in the comment section
Thank you for taking time to comment. It is much appreciated.
Ray
this is a wonderful video, thank you so much....Paul in Florida
Thank you Paul for the nice comments and thank you for taking the time to comment. It is much appreciated.
Ray
The video covers an issue that has created lots of conversation and sometimes heated arguments. As I have always worked in tool rooms and had access to a surface grinder, I machined a “tumble” fixture to form, or resharpen a hss tool bit. By changing which face goes down on the chuck, I can grind the left side angle, with a minimum of side clearance, followed by the top rake angle perpendicular to the left edge, which keeps the left angle proper, followed by another fixture face change to grind the right side angle and clearance to 29.5 degrees, giving me a clean flank cut. The compound is set at 30.0 degrees.
Years ago I learned many of these lessons from my elders in the shops of my youth. “I took the path less traveled by.” Another advantage that I have found in using hss tools, ground in a fixture, is the ability to better control the left side length, which when held to a minimum, allows threading closer to a shoulder, without an ugly groove for run out.
This just another way to skin that cat, that is always running around.
Thank you Robert for commenting and sharing. It is much appreciated.
Ray
~29deg is used because
1) tools can be ground with a small error and/or mounted slightly off angle and we want to make sure the back side will always conform to the proper V shape.
2)It reduces the total load on the tool which can wear or break off the tip where it is weakest if two large chips collide there.
3)The compound angle cannot be perfectly set at 30 deg so we want to err on the side of safety which will keep the back side cutting the full V shape.
4)The chip from the leading edge erodes away the surface of the back side so by ensuring it is always being skimmed we automatically correct that erosion as it develops.
5) By placing the majority of the load on the leading edge you maintain a high and consistent pressure on the lead screw/nut assembly and all the ways to assure it does not advance erratically causing a drunken thread.
Pro tip. Once you decide your first cut depth (20-50% of total depth) the each pass is the previous pass X the square root of the current pass number.
EX start pass selected ..015 second pass of equal volume will be .015 x square root of 2 = .0212 or .0062 more. The 3rd pass would be .015 x square root of 3= .026 or another .0048 deeper and so on ....until full depth is reached.
yes, and thank you for contributing not enough. People read the comments that are left from videos if people are truly trying to understand and learn, there needs to be a two-way communication somehow videos are great but they’re not all perfect.
Thank you for contributing and thank you for taking the time to comment. It is much appreciated.
@@shopandmath I am 72 and feeling my age quite a bit now. I am still working and the company I contract with is having a hard time finding people who are fully educated.
We had a huge order of aircraft parts rejected and they were to embarrassed to ask why. They were unable to discover the defect until they mentioned it to me and I said "No problem at all , in my pocket I have a thumb drive where I have the full details for any and ALL UN threads , standard or not" because I wrote an excel spread sheet specifically to calculate every parameter of every thread according to ASME formulas and standards.
Turned out the threads were to be UNJ and they didn't know the proper parameters so the bore was undersized. The fix was to simply bore the parts minor diameter up to UNJ spec and done.
Because no one in the whole company knew these things they asked me to create a course detailing UNJ threads to be given to the QC and to all operators. I did that but we have not implemented it yet. A full course academy is envisioned.
There are a lot of things that used to be done that are not done now but still are valid and there are some things that no longer serve any use. Thats why the history of these things matters.
People need to know WHY to do it not just WHAT to do.
The course you’re planning sounds really interesting. Wish you all the best with it.
Ray
The Mazak CNC lathes in the shop where I worked did, indeed, cut threads with a 30° feed.
The argument is usually that a big, pro lathe has the rigidity to handle a plunge cut, but that's not the point. Often the part rigidity cannot.
You are right we just tried it on our new cnc lathe today, a 5mm pitch thread on 48 dia with overhang of 156mm from chuck face didn't come out appealing.Looks like we will have to use tail stock to support the end.
Thank you for sharing. It is much appreciated. Hopefully others take the time to read the comments as well.
Ray
G92 canned cycle is a zero degree feed in threading cycle (Fanuc). G76 can also be utilized by specifying the angle of infeed to 00.
Thank you for sharing Jim. It is much appreciated.
What you say about flank versus radial feed could be said to have some relevance for a home ground form tool, but if you look at a modern full form threading insert it has a rake angle on the leading and trailing edge. Surely this implies the intention for it to cut on both sides.
For fine thread pitches many threading insert manufacturers recommend straight in feeding at 90° to the workpiece Centreline. Only when the thread helix gets steeper and the thread form deeper do they then specify feeding the tool in at the half thread angle.
First of all, thank you for taking the time to comment it makes the chats nicer, and everybody gets to see different opinions, and how other people do things
You can cut full threads without any problems using indexable tool because the tip is much stronger than let’s say high-speed steel, but even CNC machines go in at 30° and only cut with the leading like of the cutter because the tool can handle it not all of the material which would cause deflection in some cases
And also in some cases, like when I teach my level three class, and we do multiple start threads, we set the compound rest parallel to the Z axis
Feed our tool to depth with the cross slide, and then advance the compound rest one pitch to create multiple start threads
Thank you for commenting. It is much appreciated.
Ray
I've seen some thread like your photo; it's usually after some gorilla over torqued a nut & it re-modeled the thread during it's one way departure.
Also seen in on a gear/pulley puller, too, now that I think about it.
Very well done vid.
Thank you for the nice comment and thank you for taking the time to comment. It is much appreciated.
Ray
that is also similar to threads on big guns like on battle ships on the breach block. buttress threads.
actually the 60 degree thread looks very much like a sawtooth buttress thread . i did one once on a large nut 300 mm id for a tierod on a 2500 ton press . the thread was 33 degree total instead of 60. 3 degree on one side and 30 on the other. used a 35 degree insert cutter mounted to a shank and angled on the shank to give the 3 degree on one side but 32 on the other which still worked because all force was on the 3 degree side and it was internal thread so the 32 degree just gave extra clearance on the back side.. did this on a vertical cnc machining center as a thread milling operation.
looked like what you showed as wrong except it was 35 degrees total included angle .
Thank you for sharing
I was wondering what the buttress thread was used for today
Some people have replied back with hydraulics. Now I’m guessing with such a large tonnage machine. It’s a moulding machine. ?
Thank you for commenting and thank you for taking the time to comment. It is much appreciated.
Ray
Excellent video. Thank you.
Ken, thank you for the nice comment and thank you for taking the time to comment. It is much appreciated.
Should be 29 1/2 degree, not 29, this is so the right side of the tool will lightly skim the "back side" of the thread and the left side will be doing the majority of the cutting. But what do I know, I've only been doing this for 40 years! Lol
Actually the 1 degree shy of 30 is back relief for the threading tool. I have an alignment pin drilled at 29.9 on my HLV. I've been chewed for doing it, but I do a lot of precision threading on camera and optical adapters. Some of those get into 40 TPI or more. 29 wont do it on that scale.
Don't think he watched the video.
I saw the title of the video and was going to say the exact same thing 😊
I honestly don't know anyone that changes cross angle to cut threads. Mainly because it changes the tool offsets when you rotate the cross slide. I converted my bench top sized lathe to CNC though and use a python script I wrote to generate gcode for the thread parameters I am cutting. Maybe they teach this in trade schools but threads can be cut without doing that easily even on a non cnc lathe. I think that the method should be taught from the start to preserve your DRO values and tooling offsets
Here is very common the parallel method. I set the angle at 90, effectively getting a 60 degrees point. After several pases, lets say somewhat around 25% of the depth, i advance the compound about 0.05 mm in each subsequent pass, this results in the leading edge doing the cutting. This technique is nothing new and is taught here in Spain in the first semester of professional training.
Excellent
Thank you for sharing. It is much appreciated.
A few other people have commented about doing this exact same process I think that they were from Australia, but this method is used all over the world as well
Thank you for contributing to the conversation. It is much appreciated.
Ray
I also frequently use pretty much the same technique as you describe here. Both methods work very reliably. On very fine pitched shallow thread forms I only use the indeed on the cross slide.
That's not an incorrect thread, it's a proprietary thread that only works with proprietary nuts that cost 50x what normal nuts do... some would call it an "apple" thread.
A hybrid buttress thread form🤣
@@howardosborne8647 I actually just got a lathe a few weeks ago, and the very first threads I cut were exactly like this, because my compound scale is labeled the other way. I was thinking though that these look like hose barbs, and then wondered why barbed fittings aren't made with a thread, instead of just rings? That way, you could press the hose on to the fitting, just like a regular barb, but if they were threads, you could unscrew the fitting off of the hose after it's been on there for a while with a clamp, saving having to cut the hose open, or have to pry it off the fitting like you have to do with straight barbs!
Proper Threading inserts are designed to feed in a Zero Degrees, those designed for this collapse the chip, much the way a Carbide parting/ grooving insert does. A CNC program written this way only shows a succession of deeper cuts with no angle. This can be altered to several different thread cutting techniques, that only CNC machines can allow. When Using carbide for threading in a manual lathe, surface speed is more of problem, so much depends on the operators skill. HIGH SPEED STEEL threading tools are RARELY ground to produce the correct thread form, and they are never ground for the ultimate in threading topping.
I’ve noticed some lathes have 0° on X and some have 0° on Y. My lathe needs to be set at 60° to do 30°. If you set it at 29° you’ll infeed 60° and get the buttress looking thread.
Yes, I agree not all lathes are created the same. It depends if the axis is zero or zeros perpendicular to the Z axis.
The reason I made this video is because I’m having about two students every semester making the same mistake over and over again that is also why I brought it down to the extreme basics so that anyone who watches the video can understand and see the different angles
Thank you for sharing and thank you for taking the time to comment. It is much appreciated.
@@shopandmath Do you teach why what they think is X is actually Z and there is no Y?
nice job
Thank you for the nice comment and thank you for taking time to comment. It is much appreciated.
Ray
29 degrees is only appropriate for American and Metric threads with a 60 degree angle, An adjustment needs to be made if cutting a Whitworth thread.
That is correct. The Whitworth thread is 55°. I don’t know of anyone who uses that anymore or an application .
I have a 74 MG midget and it has some Whitworth threads on it. The nice thing about that is they’re the same pitch to upgrade or modernize all you need to do is run a standard tap through it, and all of a sudden it becomes a 60° thread
Do you know of any applications or modern uses for Whitworth thread
Thank you for commenting and thank you for taking the time to comment. It is much appreciated.
Ray
@@shopandmath Re-tapping BSW/BSF threads to the 60° equivalent works fine in most cases. However ½” BSW has thread count of 12 TPI and ½” UNC has a thread count of 13 TPI. (ITYF there are also different pitches between corresponding UNF and BSF threads too). Frustratingly close but not recommended for re-tapping for anything but the least critical applications.
I'm actively involved with a UK heritage railway and almost all of our equipment relies on BSW or BSF threads despite almost all new work now used Metric.
Well leave other threads like BA for another day. 🤣.
Interesting...as always.
Thank you Jay for the nice comment and thank you for taking time to comment. It is much appreciated.
Ray
Don't they teach compound and supplementary angles in school anymore? That's what most of this discussion seems to be addressing.
Carbide tooling does not last very long with this 1 degree drag angle on infeed. It will chip the side of the insert that barely does any work!
As a professional machinist, I would never teach the traditional angled infeed. If your lathe is set up with a DRO, you don't want to cancel the validity of your tool reference points with uncontrolled movements in an angular axis. Leave the compound alone! If it's at 90 degrees, you can tweak it forward and back to give single edge cutting on large threads. This technique is what I use. Modern laydown thread inserts with chip forming designs cut just fine on both edges with straight infeed.
As for how deep to cut, thread measuring wires are cheap and accurate. Start measuring before you've gone too far 😁. The difference between the measured PD and theoretical is how far you've got to go on the cross slide. No compound miscalculations need be remembered. It's all guessing anyways until it measures right, and theoretical PD is an ideal, but it's not best, because tolerances are a real thing. Some tolerances are one way, not the other. A too big thread for an "ideal nut" will not make you any friends with the mechanic putting your stuff together.
CNCs can cut with a staggered infeed that keep both sides of the insert engaged at slightly different chip thickness. Cleaning passes are straight infeed.
At 1:20 and 5:50, the thread formed would be useful in a device designed to push the bolt and nut, or slide, or device away from the bolt, if the matching profile was made complimentary, 61Degrees the other way. This would now be a 'Bolt Press", to separate the ball joints of a car spindle or some other thing needing to be pushed apart, it would not be good for pulling things together--(Clamping Force).
I could be wrong, but I think the thread form that you were referring to is called a buttress
I believe that it is used a lot for one-way threads that you would see on a saw vice
This thread form allows you to push the vice closed for positioning and then turn the handle to apply pressure when you want to release the pressure of the device. You back off the thread, lift up the nut and slide the vice jaw backwards.
I could be wrong, but I’m only guessing
@@shopandmath That is correct.
@@shopandmathIt is indeed known as a Buttress thread form. On a true Buttress thread neither flank is at 90° to the Centreline. The trailing flank is the side with the steeper angle but the leading flank also has a slightly shallow angle to it. The leading flank is never cut at a true 90 ° to the Centreline.
I happen to own a micrometer dating from 1888 that has this peculiar ‘non-existing’ thread with one flank at 90 dg to the axis of its spindle.
I must be missing something here, but where does your magic factor of 0.708 come from in calculating the infeed?
A full V form thread has height H, but in the unified system the outermost H/8 and the innermost H/8 are removed (some sources suggest the innermost H/4) so the thread depth perpendicular to the axis of the thread is 3/4.P/2.tan(60), which would be your infeed if plunging at 90deg, not allowing for to radius on the end of the tool. With the compound set at 29deg to the perpendicular this will be increased by 1/cos(29), so I make the magic factor 0.7426 . Pitch, or 0.7426/TPI
The formulas from the TMT book
Technology machine tools
very informative and helpful thanks
Thank you for your nice comment and thank you for taking the time to comment. It was much appreciated.
Ray
At 4:02, that number, 0.708, is a very close approximation of the 'Square Root of 2'?
Looks like those "incorrect" threads are buttress type threads used on antique firearm barrels
The only place that I knew, but threads were used was on a saw vice
To allow quick withdrawal and quick in feed of the jaw I did not know about firearms. Thank you for sharing is much appreciated.
Ray
@@shopandmath Buttress threads are fairly common in hydraulic cylinders and some well casing but the example would be backwards for those applications.
They are great for thin wall stuff where the load is only in one direction.
for the little threading I do, 0 deg and carbide inserts has been working great, and lets me rely on the DRO for the exact thread cutting depth. i think the 29 deg rule was very applicable for HSS tooling, but carbide tooling is far more forgiving with both sides engaged. and since the carbide is idexable, it is easy to turn the insert for a fresh tip. the video is also showing a bit uncommon insert for threading?
Keep in mind this video is for students learning
We have carbide indexable tooling for students to use but during common core or first year students, they must grind their own high-speed steel tool and use it
The reasoning behind this is the learning outcome from hand, grinding a form tool and carbide tips are expensive so students must use high-speed steel on their first 2 thread cutting exercises before they’re allowed to use carbide indexable cutting tools
@@shopandmath in that case, I would suggest to use and show a HSS tool in the video, just to make it more clear. and maybe a sentence about the relationship between the 60deg if the thread, and the 29deg (instead of 30deg) angle of the compound. and maybe a quick mention to a reference surface for setting that angle, just to make the orientation even more relatable (the angle overlays were a good idea).
There is a high-speed Steele cutting tool in the initial part of the video but you’re right I should have included that as more of a visual reference
And a demonstration cut would’ve been nice as well. Thank you for your comment and thank you for contributing.
Ray
@@shopandmath This comment brought back memories when I was an apprentice during late 70's and early 80's at biggest steel manufacturing plant in Australia.I haven't used any indexable insert whether turning,planing or threading even slotting.It was all cemented carbide or HSS which we had to sharpen.Not because I was apprentice because that's all they supplied.Only insert tool was ceramic button tools for rough machining rolls prior to grinding.My first encounter with indexable tools was at a private machine shop I later started working.
the tooling maybe can take it but when the shaft is small and sticking out alot it's not stiff enough and the straight method works bad unless you use the compound at 90 degrees and move it as well.
That looks like a reverse buttress thread, how did you grind the tool
More contact with one side of the thread than the other, less load resistance... less heat generated.
Thank you for sharing
And thank you for taking the time to comment. It is much appreciated.
Ray
I thought you were going to explain the amount of actual infeed per thousandth you get with the compound set at 29 degrees.
yes, in the video, there is a chart that shows how much in feed you require, but it is best to use the numbers from the three wire method to complete your final size
I also have a video on using three wires as well
Thank you for taking the time to comment and thank you for commenting. It is much appreciated.
I'm not understanding this. The shape of the thread is determined by the tool profile, and you don't feed with the compound rest, you feed with the compound slide.
It seems to me that it doesn't matter what angle you set your rest to. If the tool is perpendicular to the work, and you're feeding the slide in X, then the tool will be cutting on both sides.
What am I getting wrong here?
But we do feed with the compound not the cross slide.
@@marsterofnotrades Ahh, ok, you’re feeding with the rest. But then if you set it to 29 degrees, and then feed in X with the rest, you're going to create something akin to a buttress thread...which kind of looks like what you've ended up with in the video (I couldn't be sure...it might've just been a trick of light).
If you're feeding with the compound rest, and not the slide, how are you determining your depth of cut/pass? It seems like a mathematical nightmare. Are you checking the thread depth with thread gauges after each pass?
It seems like it'd be much easier to monitor your depth of cut via the DRO in the X axis using the cross slide.
Again, I'm probably getting something wrong. I'd love to learn a new technique, I'm just not sure I understand.
Maybe if you showed the process in the video?
This video was made for my students to help them, understand the difference in setting the compound rest angles
You can your tool to feed in perpendicular to the axis of the rotation that is not a problem, and you should get a good thread by doing so
The ideal cutting action is to have the majority of chips or material removed from the leading edge of the tool all the way around the cutting face. I hope that helps.
Ray
what multifix are you using?
if thread is left or right, does it change in this math something?
That’s an excellent question thank you for bringing it up in comment section
The math does not change the direction of the compound, rest rotation does change
We’re cutting right hand thread we want to feed from the tailstock to the headstock, and we want to rotate the compound rest towards the tail
To cut a left-hand thread, you want to feed from the heads stock to the tail stock, and you also want to rotate the compound rest towards the headstock
I hope that this helps answer your question and thank you for taking the time to comment. It is much appreciated.
Ray
Those threads look like hell
Yes, they do Scotty
And hopefully by making this video and showing it to my students, it will prevent them from making the same mistake
Thank you for commenting and thank you for taking the time to comment. It is much appreciated.
Ray
People don't get it right. When use carbide thread insert, which most people do then use only cross slide (0 degree), it will not give you anything good when trying to use the compound too.
So why are people using compound ?, it is a leftover when machinist making their own HSS grinded tool. The HSS Tool was grinded in two different angles. prefect 30 degree angle on the left hand side and 27-28 degree on the right side hand. Still the 30 degree side was aligned perpendicular to the workpiece. If the HSS tool has this shape non symmetrical shape then of course you must set your compound to 29.999 degree angle and only progress with the compound slide.
If you insist to use carbide and compound angle then you can modify the carbide insert similar to HSS tool. Grind the right-side angle to 27-28 degree and keep the fine nose radius intact (do not touch the nose radius) on the carbide insert.
If you are using full form inserts it's no big deal when machining small pitch threads up to 3-4mm but once you go bigger pitch 6mm or 4 TPI then it becomes a problem having too much contact area creates chatter.On manual lathes I always opt for variable pitch inserts which allows to go to depth or even slightly deeper on root diameter without taking too much of the flanks and then side shift to achieve correct pitch diameter resulting in good surface finish.
@@mehmettemel8725 yes you are right when machining thread size 3-4 mm or even higher pitch it will benefit of using the compound to 29- 29.9 degree. Still you will facing chatter problems on the right side of the carbide for two reasons. unless you grind the carbide insert so it can't cut on the rightside (Still keep the nose radius intact). First reason is that carbide is not as sharp as HSS tool and need some minimum chip depth for making a proper cut and using the angle of 29-30 degree does not provide enough cutting depth on the right hand side when using final spring cuts. Second reason is the carbide height measured to the center height increase for deep thread cuts (Negative angle) and HSS tool is grinded with positive angle which cuts better but is more fragile. My point is try it out using modified carbide insert for manual lathe or simply using HSS for thread
Keep the compound slide parallel with the bed and advance the tool half the depth of cut to simulate feeding in at 26.6 degrees, This gives a desirable 93% of the cutting load on the leading edge. There is no calculation for the compound feed in distance as the thread depth is simply on the cross slide.
My CNC has a default feed in angle of 29 degrees not 30.
You have asked for links to other threading videos. Here is my offering of 12 ways to cut threads.
SINGLE POINT THREADING 12 EASY WAYS - ZERO DEGREE COMPOUND, NO PLUNGING, NO TOOLS SET UPSIDE DOWN. I hope your students gain something from the video. There are several others for multi start - tapered & generating knuckle form threads.
Looks almost like a butress thread
Yes, it does
chinese machines use that oddball protractor. PITA
yes, but they’re popular because of the price
and honestly, I didn’t think this video was gonna be as big of a hit as it has been. I’m just tired of students doing the same mistake over and over again after I have explained it in class, and demonstrated it in class
Hopefully, this video will make it easier to understand
@@shopandmath Yeah I have 1 chinese and 1 American.
I don't. I feed straight in. And don't care what angle my compound is set.
No offense, but this could have been explained a lot better. While i applaud your foray into TH-cam and education, you should refine your approach. Take a minute to breathe and for things to sink in. Use better images that sit for a little bit. Let your audience digest. I got it at the end, but i didn’t catch 90% of what you were saying to me.
Thank you for your comment and I will keep that in mind when I make my next video
61-90 = -29, not 29. If you are going to do math, do it correctly.
Gary,, you got me you’re right
Thank you for pointing that out to me. Next time I do this I’ll have to double check my math.
Ray
Wow, way to nitpick the smallest thing. Shopandmath, keep doing you