Threading Chatter and ect.

[RanchhandTCR]

Afternoon guys..

So I finally got my hands on a lathe... super dangerous I know. Before yall roll your eyes to hard I know enough to get myself into trouble. (Continue eye roll) Any how I've been trying to resolve what is left of my lathe chattering issue while threading. Its extremely mild chatter and it a longer pattern rather than short. It's a used enco lathe and I've adjusted spindle bearings, replaced the bearings in the motor which was a major cause of issues. (Installed rubber isolators as well on the motor.) Single phase 220 motor btw. Checked and adjusted ways for play. Machine is anchored to concrete floor and the ways are leveled with a machinist level as well. It may be the nature of the machine that I get chatter at low RPM while threading with HSS and Carbide Threading tools (bought from travers). I can get rid of the chatter at about 400 rpm but I sure as hell ain't got the nades to thread at those speeds. I wouldn't mind some input from some experienced guys on weather I can ever expect a quality thread finish out of this machine or techniques to help a guy that's a jack of all trades and a master of none. Thanks!

FYI you won't easily offend me and I rather hear the God honest truth if you have something worth while to type out.

 

[B y r o n]

Back off the amount of material you're trying to take. Lighter cut less or no chatter providing your bits are sharp.

 

[RanchhandTCR]

Back off the amount of material you're trying to take. Lighter cut less or no chatter providing your bits are sharp.

That's a piece I failed to mention I've done as little as .002" cuts on stainless steel... and still get chatter.. the lighter cuts do keep it minimal. Thanks for the post!

 

[Just Macca]

Although some consider it blasphemy and IF your lathes headstock is threaded on do not attempt… you could consider threading in reverse away from the head stock.

 

[RanchhandTCR]

Although some consider it blasphemy and IF your lathes headstock is threaded on do not attempt… you could consider threading in reverse away from the head stock.

I've done that too still have chatter! Thanks for the post. Definitely tried alot of things I could think of!

 

[B y r o n]

That's a piece I failed to mention I've done as little as .002" cuts on stainless steel... and still get chatter.. the lighter cuts do keep it minimal. Thanks for the post!

Could it be the type of stainless you are using? Does it do the same with chrome moly steel? Is the cross slide gib locked before you begin threading?

 

[RanchhandTCR]

Could it be the type of stainless you are using? Does it do the same with chrome moly steel? Is the cross slide gib locked before you begin threading?

I've done it with chrome molly and stainless and still have the same issue. I haven't tried to lock the gib slide... at the current moment I'm gonna have to go look to see if it's got a way to lock it... (light bulb)

Thanks for the post

 

[Makinchips208]

If you can, turn the gib compound to a 29 degree angle, in-feed with the gib compound. This will allow the cutter to primarily cut with one side of the insert, reducing the cutting force.

 

[RanchhandTCR]

If you can turn the gib to the 30 degree angle, in-feed with the gib per pass, this will allow the cutter to cut with one side of the insert, reducing the cutting force.

I've got it set at 40* at the moment I haven't played with the gib angle on this last go around

 

[Makinchips208]

I've got it set at 40* at the moment I haven't played with the gib angle on this last go around

Ok. What part diameter?
Proper rpm is determined by the desired surface feet per minute (sfm) which is calculating of the diameter.
Small diameters need more rpm.

You probably already checked height of cutter in relation to spindle centerline?

 

[brad502a]

Set the compound at 29.5 degrees. Make sure tool is square with work. Move tool in to contact using cross slide. Zero the dials. Feed tool only using the compound slide (I start with a .010” cut) stopping when tool is in relief groove. Back out with cross slide and move carriage back to start. Return cross slide to zero feed a few more thou. Rise lather repeat. Make sure you use good cutting oil, do drill or vipers venom. I believe a guy on u tube tubal Cain demonstrates this, he is a retired tool and die from JD. Also make sure work is close to headstock or is supported by a live center. My 2 cents worth.

 

[nikonNUT]

3 questions...
1) How much work piece is hanging out of the lathe? I always tried for not more than half a diameter of clearance. 2) Have you tried using a tail stock and a live center to support the work piece? #) Have you (and this is tricky) tried threading without disengaging the the thread feed? Sounds weird I know but I had to do it to do with some metric threads on a non-metric thread lathe. Involves engating the thread feed, threading in, and in one deft movement retracting the threading tool with the cross feed and reversing the spindle at the same time. Reverse past the part, stop the spindel, reset the cross feed for the next pass and engage the spindle for the next trip. I was always amazed at how consistent the threads were. PITA part was on the lathe I running the thread feed lever liked to jump out of "gear" so a knee was placed on it to make sure it stayed put! I looked like a peg legged pirate and it was quite the dance but it worked.

 

[RanchhandTCR]

3 questions...
1) How much work piece is hanging out of the lathe? I always tried for not more than half a diameter of clearance. 2) Have you tried using a tail stock and a live center to support the work piece? #) Have you (and this is tricky) tried threading without disengaging the the thread feed? Sounds weird I know but I had to do it to do with some metric threads on a non-metric thread lathe. Involves engating the thread feed, threading in, and in one deft movement retracting the threading tool with the cross feed and reversing the spindle at the same time. Reverse past the part, stop the spindel, reset the cross feed for the next pass and engage the spindle for the next trip. I was always amazed at how consistent the threads were. PITA part was on the lathe I running the thread feed lever liked to jump out of "gear" so a knee was placed on it to make sure it stayed put! I looked like a peg legged pirate and it was quite the dance but it worked.

Currently I'm messing with old barrels so I'm only have 2-2.5 inches sticking past the chuck and I try to keep the too as close to the holder as I can. With such little odf the work piece sticking out my tailstock interfere with the tool. I haven't messed with leaving the threads engaged.

 

[RanchhandTCR]

Ok. What part diameter?
Proper rpm is determined by the desired surface feet per minute (sfm) which is calculating of the diameter.
Small diameters need more rpm.

You probably already checked height of cutter in relation to spindle centerline?

I'm working with 1" to 1/2" work pieces currently. With a carbide insert I run at 725 for the large diameter and 1100 for smaller diameter with a 55* profile insert. But I can achieve a good finish turning the od its when It comes to threading it go to shit. Yes I have also verified my center line.

Thanks for the post.

 

[RanchhandTCR]

Set the compound at 29.5 degrees. Make sure tool is square with work. Move tool in to contact using cross slide. Zero the dials. Feed tool only using the compound slide (I start with a .010” cut) stopping when tool is in relief groove. Back out with cross slide and move carriage back to start. Return cross slide to zero feed a few more thou. Rise lather repeat. Make sure you use good cutting oil, do drill or vipers venom. I believe a guy on u tube tubal Cain demonstrates this, he is a retired tool and die from JD. Also make sure work is close to headstock or is supported by a live center. My 2 cents worth.

I thread the way you describe except I need to adjust the angle. I use dark sulfur oil for most operations. I live in the sticks so ordering online is a pita but probably have to Bite down and order some viper venom oil and see how many times fed ex missed my 4' wide address sign. Appreciate your 2 cents

 

[brad502a]

OK, I only have enough work out of the headstock for tool/tool holder clearance. Excessive stock out of the headstock will cause chatter. I thread at 70 rpm. Slow it down

 

[brad502a]

watch this guys videos he knows what he is talking about.

 

[RanchhandTCR]

OK, I only have enough work out of the headstock for tool/tool holder clearance. Excessive stock out of the headstock will cause chatter. I thread at 70 rpm. Slow it down

I'll try to shorten my work piece. I'm trying to thread at 60-90 rpm that just where my problems are.. Thank you for the post

 

[Zane1844]

I've got it set at 40* at the moment I haven't played with the gib angle on this last go around

If your compound is set at 40 degrees, do not feed with it while threading as threads are 60 degrees. You can keep your compound at 40 degrees and feed with your crosslide, but that creates a lot of pressure.

People already added great suggestions. I'd recommended trying the tailstock, and doing spring passes after your initial cuts.

 

[brad502a]

 

[nikonNUT]

Currently I'm messing with old barrels so I'm only have 2-2.5 inches sticking past the chuck and I try to keep the too as close to the holder as I can. With such little odf the work piece sticking out my tailstock interfere with the tool. I haven't messed with leaving the threads engaged.

Now this is just me but (and I am not criticizing) if I was working with 1" O.D. stock I would have .5" hanging out past my stopping point. 2 to 2.5" past my stopping means I am working with 4" to 5" OD stock. Oh and FWIW, I thread at 150 to 240 RPM with an Iscar external laydown threading insert. 60° partial profile. I could run a ton more speed but stopping (in time) gets... difficult. I've crammed a tool or two. Also, how are you supporting the back end of the barrel? If you have 2.5" hanging out the front and 20" unsupported in the draw tube there is a lot of rotational whip going on. Whipping up a bushing for the backside to keep the work piece centered might help as well.

 

[lariat]

I just finished some stainless in the shop again. Sometimes it is goofy. I hate it. But there are solid suggestions above. The thing I would suggest is to hold it as tight to the Chuck as you can to prevent harmonics/vibrations and before you do that do a full check to ensure nothing is even slightly loose or hanging too far out. Then try what these guys are saying.

It can be frustrating but when you get it right on stainless it’s amazing. I keep notes on each type of stainless and each type of part. At least it gives you a starting point next time.

 

[lariat]

Now this is just me but (and I am not criticizing) if I was working with 1" O.D. stock I would have .5" hanging out past my stopping point. 2 to 2.5" past my stopping means I am working with 4" to 5" OD stock. Oh and FWIW, I thread at 150 to 240 RPM with an Iscar external laydown threading insert. 60° partial profile. I could run a ton more speed but stopping (in time) gets... difficult. I've crammed a tool or two. Also, how are you supporting the back end of the barrel? If you have 2.5" hanging out the front and 20" unsupported in the draw tube there is a lot of rotational whip going on. Whipping up a bushing for the backside to keep the work piece centered might help as well.

This brings up a good point. I use sleeves and bushings to prevent that bullshit whipping on the part that isn’t held in the chuck. There’s more vibration there than one would think and there is no reason to think that it isn’t transferring to some degree to the area being threaded.

 

[RanchhandTCR]

Now this is just me but (and I am not criticizing) if I was working with 1" O.D. stock I would have .5" hanging out past my stopping point. 2 to 2.5" past my stopping means I am working with 4" to 5" OD stock. Oh and FWIW, I thread at 150 to 240 RPM with an Iscar external laydown threading insert. 60° partial profile. I could run a ton more speed but stopping (in time) gets... difficult. I've crammed a tool or two. Also, how are you supporting the back end of the barrel? If you have 2.5" hanging out the front and 20" unsupported in the draw tube there is a lot of rotational whip going on. Whipping up a bushing for the backside to keep the work piece centered might help as well.

Yaya keep bragging!!!!! I can pull out, rebuild and have a isb Cummins running in a weekend! Im Just ribbing ya.


I have a spider on the back side of the tube along with a viper tools trueing fixture (for the shorties. I know I'm hanging out farther than most but I've got the training wheels on and I remember when I crashed the jet lathe back in college... and I am trying to avoid that.. I already tried threading at 250rpm did great until I didn't lmao its not the speed that scares me its getting the half nut unlocked in time I dont have a brake on this machine so when it goes.... it goes... I'll go and chop up some more old stock and see if I can't mash everyone's info and see if I can make something out all of it. Appreciate all the info and advice!

 

[RanchhandTCR]

I just finished some stainless in the shop again. Sometimes it is goofy. I hate it. But there are solid suggestions above. The thing I would suggest is to hold it as tight to the Chuck as you can to prevent harmonics/vibrations and before you do that do a full check to ensure nothing is even slightly loose or hanging too far out. Then try what these guys are saying.

It can be frustrating but when you get it right on stainless it’s amazing. I keep notes on each type of stainless and each type of part. At least it gives you a starting point next time.

Yea ive got speeds and feeds fiqured out and got a note book going for different metals and sizes and ect. Just the damn chatter threading is pissin me off. Rebuilding my motor got it where my stainless Comes out like a mirror... just does not finish nice while threading.. everything I've done has improved just got this last hurdle to cross. Thanks for the post.

 

[RanchhandTCR]

If your compound is set at 40 degrees, do not feed with it while threading as threads are 60 degrees. You can keep your compound at 40 degrees and feed with your crosslide, but that creates a lot of pressure.

People already added great suggestions. I'd recommended trying the tailstock, and doing spring passes after your initial cuts.

Definitely gonna make some changes and see what else I can mess up! Appreciate the post.

 

[DAMNKID]

Just curious what threading insert are you using?

 

[RanchhandTCR]

Just curious what threading insert are you using?

Now that's an answer I don't have currently.. I have a few HSS 60* tools and a smattering of carbides.. I have everything from cheap to a few $20 a piece inserts.

 

[Yondering]

I know I'm hanging out farther than most but I've got the training wheels on and I remember when I crashed the jet lathe back in college... and I am trying to avoid that..

Well, that's why you're getting chatter. Doesn't matter if you're nervous or not, too much unsupported stock WILL cause chatter. You have to either set it closer to the chuck, or let it stick out a lot further and stabilize it with a live center in the tailstock. Either way should work well, but what you're doing won't. Not much use chasing other solutions until you make this right.

And BTW, 60-90 rpm is plenty slow enough. Way slower than necessary IMO, especially for barrel threads at 24-28 tpi. Occasionally I'll slow down to 200 rpm on something where there's just no room for error, but often just stay at ~800 rpm. Not saying you should start fast, by any means; I'm saying you don't need to try to go any slower than what you're already doing, and should be able to speed up as you get more lathe hours under your belt.

 

[Yondering]

3 questions...
1) How much work piece is hanging out of the lathe? I always tried for not more than half a diameter of clearance. 2) Have you tried using a tail stock and a live center to support the work piece? #) Have you (and this is tricky) tried threading without disengaging the the thread feed? Sounds weird I know but I had to do it to do with some metric threads on a non-metric thread lathe. Involves engating the thread feed, threading in, and in one deft movement retracting the threading tool with the cross feed and reversing the spindle at the same time. Reverse past the part, stop the spindel, reset the cross feed for the next pass and engage the spindle for the next trip. I was always amazed at how consistent the threads were. PITA part was on the lathe I running the thread feed lever liked to jump out of "gear" so a knee was placed on it to make sure it stayed put! I looked like a peg legged pirate and it was quite the dance but it worked.

FYI, there's an easier way to cut metric threads on an inch lathe. It maintains that same spindle to lead screw relationship but allows you to disengage the half nuts like you normally would for inch threads.

- Pick a number on your threading dial (I usually just choose #1): you're going to engage at that one point, and that point only. Do not engage the half nuts anywhere else.
- Start threading as normal, engaging at #1 on the dial.
- When the tool approaches the shoulder, disengage the half nuts and immediately stop the lathe. If you have a brake it's even easier, but if not, just watch the thread dial - it shouldn't go around a full turn, but if it does, pay attention to that and make sure you repeat it exactly in reverse.
- DO NOT move the lathe carriage by hand in either direction, leave it exactly where it stops. Only the lead screw should move the carriage in either direction. This is important.
- Back off the cross slide as you normally would.
- Start the lathe in reverse, now watch the thread dial and engage the half nuts when it unwinds back to that same #1 spot again.
- Depending on your setup (using a tailstock, or just the chuck) either stop the lathe while leaving the half nuts engaged, or disengage and follow step 3 above again, just in the other direction.
- Now you're ready to start the next pass, always using that #1 spot on the thread dial.

As long as you engage the half nuts in that same spot every time, AND (the important part here) that thread dial isn't allowed to get a full turn or more out of time, you'll maintain that critical relationship between the spindle and the lead screw - giving the same effect as leaving the half nuts engaged all the time, but without the hassle and danger of running into a shoulder or hitting the tailstock in reverse.

Explained differently - even though you're disengaging the half nuts and allowing the lathe to continue turning a little bit, you're using the thread dial (and not moving the carriage) and reversing the lathe to engage the half nuts in the same spot again. Then doing the same process again in reverse at the right hand side of travel if necessary.

Try it on a piece of scrap aluminum to verify you understand the process - it's simple once you get it, but might take a minute to wrap your head around it.

 

[iceng]

Most people have answered it here. Offset tool post and top slide are a cure. Correct tool height is a cure. Correct cutting oil for thr material is a cure. Post a pic, helps diagnose it.

I was threading today at 1800rpm..... on my CNC.

Manually i do 180rpm to 260rpm, depending on what it is.

 

[RanchhandTCR]

Most people have answered it here. Offset tool post and top slide are a cure. Correct tool height is a cure. Correct cutting oil for thr material is a cure. Post a pic, helps diagnose it.

I was threading today at 1800rpm..... on my CNC.

Manually i do 180rpm to 260rpm, depending on what it is.

Definitely got great answers and the 2nd set of eyes rule is helping me out. I thought I had some pics but guess I didn't keep them.. I'll go and see if I can improve everything and update everyone. I don't quite have the confidence to run at 200 plus rpm but it's just a mater of time for me between all my other projects.

Thanks for the post!

 

[CNC-Dude]

You may have to accept that this is the best your lathe can achieve. Since it's used, the spindle can have excessive wear/play that is preventing it from producing better, consistent results.....

 

[nikonNUT]

This brings up a good point. I use sleeves and bushings to prevent that bullshit whipping on the part that isn’t held in the chuck. There’s more vibration there than one would think and there is no reason to think that it isn’t transferring to some degree to the area being threaded.

Somewhere on our security cam footage is a video where one of our jackasses was running a 2" x 160" long ram with about 90" of unsupported material hanging out the back. Picked the wrong program and the lathe (TL-3B) went to max speed for constant surface speed reasons instantly. About 3 seconds later the rod bent 90-ish degrees and promptly dug a trench in the concrete and almost took out our big drill press and our hydraulic cylinder servicer! Bossman was not happy.

Here is a fun "little" project I got to do back in the day. 7" OD x 5" ID x 270-ish inches long. Lots of backwards, upside down threading. Figured I was going to die the moment I started the spindle. I did blow every roller in the steady rests instantly. Used an old 6 foot lathe to hold the second steady rest...

 

[LeftyJason]

Somewhere on our security cam footage is a video where one of our jackasses was running a 2" x 160" long ram with about 90" of unsupported material hanging out the back. Picked the wrong program and the lathe (TL-3B) went to max speed for constant surface speed reasons instantly. About 3 seconds later the rod bent 90-ish degrees and promptly dug a trench in the concrete and almost took out our big drill press and our hydraulic cylinder servicer! Bossman was not happy.

Here is a fun "little" project I got to do back in the day. 7" OD x 5" ID x 270-ish inches long. Lots of backwards, upside down threading. Figured I was going to die the moment I started the spindle. I did blow every roller in the steady rests instantly. Used an old 6 foot lathe to hold the second steady rest...

View attachment 8177123

I used to run a tl3b. Oilfield. Worst parts I had to run on it were 3/4" taper per foot double shoulder buttress threads. Parts were 1/2" wall aluminum 30' long. Max rpms we could run was 22ish. Had 3 different diameters. Core catcher pipe.

Also got to chase tapered threads on drill pipe. That's fun.

These days I run threads in inconel at 3rpm. On a cnc crush form grinder.

 

[RanchhandTCR]

You may have to accept that this is the best your lathe can achieve. Since it's used, the spindle can have excessive wear/play that is preventing it from producing better, consistent results.....

Yea ill give the info and advice recieved a try if that's the best it can do with the little talent I've got then it is what it is.

 

[RanchhandTCR]

Somewhere on our security cam footage is a video where one of our jackasses was running a 2" x 160" long ram with about 90" of unsupported material hanging out the back. Picked the wrong program and the lathe (TL-3B) went to max speed for constant surface speed reasons instantly. About 3 seconds later the rod bent 90-ish degrees and promptly dug a trench in the concrete and almost took out our big drill press and our hydraulic cylinder servicer! Bossman was not happy.

Here is a fun "little" project I got to do back in the day. 7" OD x 5" ID x 270-ish inches long. Lots of backwards, upside down threading. Figured I was going to die the moment I started the spindle. I did blow every roller in the steady rests instantly. Used an old 6 foot lathe to hold the second steady rest...

View attachment 8177123

Can I use that on my 22 creedmoor? Yea im not in that category of giant shit to deal with.. all my cool "dumbass" stories involve chains and heavy trucks lol

 

[LeftyJason]

Can I use that on my 22 creedmoor? Yea im not in that category of giant shit to deal with.. all my cool "dumbass" stories involve chains and heavy trucks lol

Might be a little big. Looking it up it had 25" between dual chuck capacity. So maybe if you had a long enough barrel. Part sticking out of the cover is at least 6" diameter. Dual 25" chucks with 8.5" bore.

This is the back of the front chuck. 4 jaw manual. Back chuck was a 3 jaw scroll.

 

[lariat]

I need that machine right now. Currently cutting 14" aluminum round bar, drilling and boring 12" deep, then adding acme threads. Then to the mill it goes. Welding and jigs are my life at the moment. Ugh.

 

[Tokay444]

If you can, turn the gib to a 29 degree angle, in-feed with the gib. This will allow the cutter to primarily cut with one side of the insert, reducing the cutting force.

The gib adjusts slack on the bed ways. The compound rest is what you set at 29°.

 

[nikonNUT]

Can I use that on my 22 creedmoor? Yea im not in that category of giant shit to deal with.. all my cool "dumbass" stories involve chains and heavy trucks lol

It would make one hell of a suppressor me thinks! I wanted a chunk of the old rod... Would have made one hell of a 5" cannon barrel!

 

[Makinchips208]

The gib adjusts slack on the bed ways. The compound rest is what you set at 29°.

You are correct. Sorry, I used the wrong word. Not gib angle, compound angle. Thanks for catching that!

I've got it set at 40* at the moment I haven't played with the gib angle on this last go around

Please note the correction.

 

[RanchhandTCR]

You are correct. Sorry, I used the wrong word. Not gib angle, compound angle. Thanks for catching that!

Please note the correction.

Oh man I already cut it off to weld it at the new angle... joking! I knew what ya meant! Appreciate it guys thanks for helping out..

 

[RanchhandTCR]

It would make one hell of a suppressor me thinks! I wanted a chunk of the old rod... Would have made one hell of a 5" cannon barrel!

I'd like to see the atf confiscate that one lol.

 

[nikonNUT]

Might be a little big. Looking it up it had 25" between dual chuck capacity. So maybe if you had a long enough barrel. Part sticking out of the cover is at least 6" diameter. Dual 25" chucks with 8.5" bore. View attachment 8177165

This is the back of the front chuck. 4 jaw manual. Back chuck was a 3 jaw scroll. View attachment 8177167

I need that machine right now. Currently cutting 14" aluminum round bar, drilling and boring 12" deep, then adding acme threads. Then to the mill it goes. Welding and jigs are my life at the moment. Ugh.

Y'all should see my ST-50! Converted to 30” pneumatic chucks because fuck a bunch of T-Handle on those beasts! For reference I can fit my 260lb 6 ft frame in that corner behind the chuck.

 

[RanchhandTCR]

Y'all should see my ST-50! Converted to 30” pneumatic chucks because fuck a bunch of T-Handle on those beasts! For reference I can fit my 260lb 6 ft frame in that corner behind the chuck.

View attachment 8177308

I'll come over and see how fast I can break it.

 

[Tokay444]

Needs moar Mazak.

 

[nikonNUT]

I'll come over and see how fast I can break it.

Please don't.... We just replaced the piston cups on those chucks. They were $4K apiece!

Needs moar Mazak.

Maybe I'm an old school Fanuc guy but fuck that reverse polock programming! :lol: Nah, man, they do make good machines! My dream machine is a <not sure how many> axis DMG! Makes my brain melt!

 

[Tokay444]

Please don't.... We just replaced the piston cups on those chucks. They were $4K apiece!

Maybe I'm an old school Fanuc guy but fuck that reverse polock programming! :lol: Nah, man, they do make good machines! My dream machine is a <not sure how many> axis DMG! Makes my brain melt!

Their Titanium Crown video is better.
We eat G-Code faster than the current DMGs though.

 

[JBoomhauer]

You may have to accept that this is the best your lathe can achieve. Since it's used, the spindle can have excessive wear/play that is preventing it from producing better, consistent results.....

Some cheap lathes just do not have the rigidity to make good threads.