Help with lathe runout
Help with lathe runout
Ok. To start I have an Enco 12X36 lathe and have a 3 jaw chuck that came with the lathe. I have been piddling around for the last month learning how to use it and have made a few little projects. So I got my form 1 back and was going to chuck my stainless tube up, square the end up and part it off to the length and send it off to get engraved. My problem is that I have loads of runout and don't know how to correct it. Example: I put the tube in and clamped it down, about 1" sticking out past the end of the jaws my runout is about .020. Loosened chuck up, pulled material out about 14" and used the live center on the end and still have .010 runout in the center. We checked the material against a flat surface with a feeler guage and it is dead nuts. I chucked the round stock up and same runout. Took the chuck off and cleand the hell out of everything and checked runout on spindle and chuck both were less then .001. So I have to ASSume the problem is with the jaws and it just flat out being a cheap ass china lathe and I need a new chuck, please someone say I'm right and tell me what kind of chuck I should be looking at. I don't really want to screw up my material.
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jimmym40a2
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David Hineline
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Each jaw was put into a particular slot when it was made and then center bored to make sure the run out was minimal. If a previous owner or yourself backed the jaws out and removed them for cleaning, then put them back into different slots in the chuck then it is not going to close correctly in the center.
Take the jaws out by backing out with the chuck handle and check each jaw for a number or some type of mark as to which slot they should go into, if there are no indications then try each jaw in each slot and see which combination gives the least run out.
Ok so now if you still have this much runout, the jaws need to be trued up. Basically the jaws need be opened up kinda wide then tensioned in like they are grabbing on something with a spider ring and set screws or whatever. Then as the chuck is turning slowly go in with a stone on a tool post grinder and re-face the chucks. Also have an index mark on the chuck body and spindle backplate so it always goes on and off the same way.
Here is a 6 page discussion on another board of how to do it.
http://www.chaski.org/homemachinist/vie ... jaw+chucks
Take the jaws out by backing out with the chuck handle and check each jaw for a number or some type of mark as to which slot they should go into, if there are no indications then try each jaw in each slot and see which combination gives the least run out.
Ok so now if you still have this much runout, the jaws need to be trued up. Basically the jaws need be opened up kinda wide then tensioned in like they are grabbing on something with a spider ring and set screws or whatever. Then as the chuck is turning slowly go in with a stone on a tool post grinder and re-face the chucks. Also have an index mark on the chuck body and spindle backplate so it always goes on and off the same way.
Here is a 6 page discussion on another board of how to do it.
http://www.chaski.org/homemachinist/vie ... jaw+chucks
NFA shooters blow their load with only one pull of the trigger.
You may be on to something, we did remove the jaws several times on different projects. They are numbered 1, 2 and 3 so we figured as long as they were reinstalled in that order it would still work correctly. I will try that tonight and see what happens. I did order a 4 jaw inde. for precision stuff. Thanks.
A good 3-jaw (or any self-centering) chuck, properly installed, with the jaws in the right places is only accurate to 0.003"-0.005". Because the runout is also dependent on the scroll in the back of the chuck the runout will vary with the diameter of the work being grasped. 'Sparking in' a chuck as David Hineline suggests does true the jaws, but does not address errors in the scroll except at the one diameter where the jaws were trued. Exceptions are self-centering chucks with adjustable back-plates (set-tru, etc).
The proper chuck for precision work is either a 4-jaw or a set-tru style chuck, period. (and a 3-jaw with .020" runout is a useless piece of crap and should be discarded if it can't be made to get down to .005" or less.)
If you need a decent quality import chuck I've had pretty good luck with 'Bison' (Polish) - they're not PBA, but they do the trick.
GsT
The proper chuck for precision work is either a 4-jaw or a set-tru style chuck, period. (and a 3-jaw with .020" runout is a useless piece of crap and should be discarded if it can't be made to get down to .005" or less.)
If you need a decent quality import chuck I've had pretty good luck with 'Bison' (Polish) - they're not PBA, but they do the trick.
GsT
50 BMG Site:
www.hevanet.com/50shooter
www.hevanet.com/50shooter
My intent was to square off an end, pull the tube out to what length I wanted and part it off. The id on my seamless is .75 so I don't have any work to do to that. But I have to turn my od down (same dia. as my Mark III bbl) for asthetics. I was going to put between centers and turn it down after I parted it off then polish it up real nice before it gets engraved. Good plan bad plan?
I think people need to clarify.
3 jaw chucks are perfect for most work. 4 jaw chucks are perfect for precision work.
I would NEVER get rid of a 3 jaw for a 4 jaw, every time you use it you'd have to indicate your parts and that would be terribly time consuming.
I actually own a 4 jaw chuck that I've never used. my 3 jaw chuck is accurate as I need for everything I do on that lathe. my new one needs a little work but I think I can get it down there. If not I plan to make a spider for barrels.
Jon
3 jaw chucks are perfect for most work. 4 jaw chucks are perfect for precision work.
I would NEVER get rid of a 3 jaw for a 4 jaw, every time you use it you'd have to indicate your parts and that would be terribly time consuming.
I actually own a 4 jaw chuck that I've never used. my 3 jaw chuck is accurate as I need for everything I do on that lathe. my new one needs a little work but I think I can get it down there. If not I plan to make a spider for barrels.
Jon
The first thing I would do is check the machine before the chuck.
Get some round stock material (aluminum, steel - whatever) at least an 1 in in diameter. Protrude it 1" or so from the chuck and clamp it down. Make sure to always tighten the chuck on the tightening key hole. This will usually be marked on the chuck. This produces more consistent results.
Next take a cut. You only need to skim the surface. Make sure you get a smooth finish. Then take a test indicator and measure runout. It should be unmeasurable on a thou graduated test indicator with a good machine. This test would show you if there's any spindle problems.
Next using a 1" dia. of material like above (you can use the same piece). Chuck it up and center drill it for a center. Then chuck it up with 6-12 inches or so (depending on size of machine) of material protruding. Support it with a live center. Take a cut all the way down the length of material.
Measure the diameter of the shaft (with a micrometer - not calipers). If it tapers your tail stock may need adjustment.
Get some round stock material (aluminum, steel - whatever) at least an 1 in in diameter. Protrude it 1" or so from the chuck and clamp it down. Make sure to always tighten the chuck on the tightening key hole. This will usually be marked on the chuck. This produces more consistent results.
Next take a cut. You only need to skim the surface. Make sure you get a smooth finish. Then take a test indicator and measure runout. It should be unmeasurable on a thou graduated test indicator with a good machine. This test would show you if there's any spindle problems.
Next using a 1" dia. of material like above (you can use the same piece). Chuck it up and center drill it for a center. Then chuck it up with 6-12 inches or so (depending on size of machine) of material protruding. Support it with a live center. Take a cut all the way down the length of material.
Measure the diameter of the shaft (with a micrometer - not calipers). If it tapers your tail stock may need adjustment.
Tornado Technologies
Mailing Address:
22115 NW Imbrie Drive #181
Hillsboro OR 97124
PH: (503)690-8000
Web: www.tornado-technologies.com
Mailing Address:
22115 NW Imbrie Drive #181
Hillsboro OR 97124
PH: (503)690-8000
Web: www.tornado-technologies.com
AAA's advice is excellent. JFettig - if you use a 4-jaw much that centering process gets to costing you about 60 seconds to get within 0.001" - it's just a matter of practice and having an indicator that's convenient. I use a dial indicator mounted in a custom QC toolholder and can center something round up fast. Centering square work takes just a little more time.
I recommend against parting off tubing in the lathe - it's easy to 'snag' as it breaks through. Just saw it off then dress the end in a lathe.
If I could only have one chuck it would be a 4-jaw. A 4-jaw can do anything a 3-jaw can do (yes, you can grasp hex stock, because the jaws are independent, they don't have to land on a flat spot - but a 3-jaw can't grasp square stock...) and the accuracy is up to the user. Turning between centers is another good way to achieve accuracy (assuming tailstock alignment) but it doesn't help with cutting internal threads...
GsT
I recommend against parting off tubing in the lathe - it's easy to 'snag' as it breaks through. Just saw it off then dress the end in a lathe.
If I could only have one chuck it would be a 4-jaw. A 4-jaw can do anything a 3-jaw can do (yes, you can grasp hex stock, because the jaws are independent, they don't have to land on a flat spot - but a 3-jaw can't grasp square stock...) and the accuracy is up to the user. Turning between centers is another good way to achieve accuracy (assuming tailstock alignment) but it doesn't help with cutting internal threads...
GsT
50 BMG Site:
www.hevanet.com/50shooter
www.hevanet.com/50shooter
I am a toolmaker by trade and have equipment at home as well. Your 3 jaw chuck will be your best friend about 95% of the time. A 4 jaw is a must have as well. Your best bet would be to bore your chuck jaws on your machine. Get some dykem bluing or use a sharpie marker and color up your jaw surfaces. Chuck a milling spacer or a piece of round stock slightly behind the jaws. LIGHTLY make passes with a carbide tipped boring bar until the sharpie or dykem cleans up. Remove the chucking ring and your should be good to go. I have a Logan 11X36 heavy (big through hole) and once leveled properly and the chuck bored in it's very accurate.
Now if I had a DRO on it......
Now if I had a DRO on it......
Last edited by cal50 on Wed Feb 04, 2009 3:12 pm, edited 1 time in total.
3-jaw is for times where you take a piece of stock and do a series of operations and never put it back. Think line work and mass production.
4-jaw is for any time you need to do accurate work, offset work, or further work on previous pieces. Use one for cams or precision work for something like center drilling from both ends.
4-jaw is for any time you need to do accurate work, offset work, or further work on previous pieces. Use one for cams or precision work for something like center drilling from both ends.
Cal50's idea
Like cal50 I am also a tool and die maker by trade and have equipment at home .. (it's a disease shared by many toolmakers)
On my Victor 1640B
I had poor luck trying to bore the jaws on my 3 jaw. No mater how a secured it either the the backlash was going the wrong way or the slop in the chuck made the jaws tilt when I clamped behind them if you do not have access to other machines do it EXACTLY like cal50 says and you will be in good shape.
I chucked up on a leader pin indicated it and marked the offset on each jaw. Dressed a radius on a wheel and surface ground whatever was marked on the jaw off to get it back on center. I now have my cheap 3 jaw running within .0007 on good ground stock. With material sticking out 12" or so you are that the mercy of the quality of the chuck. If the chuck slop in it in the Z axis at the chuck jaws your only going to be able to do so much with boring and shimming. If you can't buy a 4 jaw right now you can do a lot with brass shim and time.
Good luck .. K
On my Victor 1640B
I had poor luck trying to bore the jaws on my 3 jaw. No mater how a secured it either the the backlash was going the wrong way or the slop in the chuck made the jaws tilt when I clamped behind them if you do not have access to other machines do it EXACTLY like cal50 says and you will be in good shape.
I chucked up on a leader pin indicated it and marked the offset on each jaw. Dressed a radius on a wheel and surface ground whatever was marked on the jaw off to get it back on center. I now have my cheap 3 jaw running within .0007 on good ground stock. With material sticking out 12" or so you are that the mercy of the quality of the chuck. If the chuck slop in it in the Z axis at the chuck jaws your only going to be able to do so much with boring and shimming. If you can't buy a 4 jaw right now you can do a lot with brass shim and time.
Good luck .. K
One more thing
If it's a Cam-lock chuck. Rotate the chuck to each positing and see which works best. Mark the chuck and always use that position.
If the 3 jaw chuck has more than one spot you can tighten it up by try all of them and use the one that gives the best results. Backlash and slop can do funny things. As long as it is doing the same thing every time it can be dealt with.
It won't help with a short tube but with longer items you can make what I call a spider and mount it on the the backside of your lathes through tube.
It's just a ring with 4 LONG screws or set screws with brass ends you have added . With a long barrel you use it like a 4 jaw to get the barrel running true.
If the 3 jaw chuck has more than one spot you can tighten it up by try all of them and use the one that gives the best results. Backlash and slop can do funny things. As long as it is doing the same thing every time it can be dealt with.
It won't help with a short tube but with longer items you can make what I call a spider and mount it on the the backside of your lathes through tube.
It's just a ring with 4 LONG screws or set screws with brass ends you have added . With a long barrel you use it like a 4 jaw to get the barrel running true.
Good advices so far
But sins its for a one part job buying a 4 chuck might be overkill
As AAA did write "Make sure to always tighten the chuck on the tightening key hole. This will usually be marked on the chuck. This produces more consistent results. ""
But try this (sometimes you can be lucky )only tightening it lightly
Then test you runout ,if ok tight more
If the runout isnt god ,go to the next (clockvise on the chuck looking at it ) tighting it a bit more ,check runout again
If it got better ,go to the last hole and fully tighten
this can sometimes take up the play that is in all chucks (more or less )
If you didnt have luck ,try again but starting at another hole
Lastly you can shim the jaw that seams to be to small with paper
You aint going to aply much force anyway ,or you will deform you tube
But sins its for a one part job buying a 4 chuck might be overkill
As AAA did write "Make sure to always tighten the chuck on the tightening key hole. This will usually be marked on the chuck. This produces more consistent results. ""
But try this (sometimes you can be lucky )only tightening it lightly
Then test you runout ,if ok tight more
If the runout isnt god ,go to the next (clockvise on the chuck looking at it ) tighting it a bit more ,check runout again
If it got better ,go to the last hole and fully tighten
this can sometimes take up the play that is in all chucks (more or less )
If you didnt have luck ,try again but starting at another hole
Lastly you can shim the jaw that seams to be to small with paper
You aint going to aply much force anyway ,or you will deform you tube
This can make a worn set of jaw as good again ,just remember to tell that the hole used for tightening the jaws when doing this if´s the hole you have to use from now on (use thew hole that is marked )cal50 wrote:I am a toolmaker by trade and have equipment at home as well. Your 3 jaw chuck will be your best friend about 95% of the time. A 4 jaw is a must have as well. Your best bet would be to bore your chuck jaws on your machine. Get some dykem bluing or use a sharpie market and color up your jaw surfaces. Chuck a milling spacer or a piece of round stock slightly behind the jaws. LIGHTLY make passes with a carbide tipped boring bar until the sharpie or dykem cleans up. Remove the chucking ring and your should be good to go. I have a Logan 11X36 heavy (big through hole) and once leveled properly and the chuck bored in it's very accurate.
Now if I had a DRO on it......
using a different hole will change the way the jaws tightens
If you own a lathe, you *need* to own a 4-jaw chuck. It's not overkill, if you use the lathe you'll use that chuck again, and again... A 3-jaw on the other hand is just a convenience.wolf wrote:Good advices so far
But sins its for a one part job buying a 4 chuck might be overkill
GsT
50 BMG Site:
www.hevanet.com/50shooter
www.hevanet.com/50shooter
GeneT wrote:If you own a lathe, you *need* to own a 4-jaw chuck. It's not overkill, if you use the lathe you'll use that chuck again, and again... A 3-jaw on the other hand is just a convenience.wolf wrote:Good advices so far
But sins its for a one part job buying a 4 chuck might be overkill
GsT
The other option is to find a 3 jaw adjustable chuck ($$$).
Then get or build a nice steady rest,taper attachment,5C Collet closer,5C collets,large diameter live center,clamp type knurl tool,aloris tool post,some good flip tip tooling and your all set!
Agreed the Set Tru style chucks are the way to go with 3 jaws.
Another option if you wanna spend big bucks is get one of the ones Cushman makes. I think it's called a combination chuck.
It has 4 jaws but has two chuck key holes. One allows the jaws to be adjusted independently and the other works the jaws like a regular 3 jaw self centering chuck. We have one and it's real fast to use as a 4 jaw.
Another option if you wanna spend big bucks is get one of the ones Cushman makes. I think it's called a combination chuck.
It has 4 jaws but has two chuck key holes. One allows the jaws to be adjusted independently and the other works the jaws like a regular 3 jaw self centering chuck. We have one and it's real fast to use as a 4 jaw.
Tornado Technologies
Mailing Address:
22115 NW Imbrie Drive #181
Hillsboro OR 97124
PH: (503)690-8000
Web: www.tornado-technologies.com
Mailing Address:
22115 NW Imbrie Drive #181
Hillsboro OR 97124
PH: (503)690-8000
Web: www.tornado-technologies.com
Even a set-true 3-jaw isn't a substitute for a 4-jaw because they still can't hold work eccentrically or hold square shapes. They are a great bit of tooling if you have the spare cash laying around. Once you've got everything you've listed you'll be all set - set to start collecting more stuff for your shop, it's never really done...cal50 wrote:
The other option is to find a 3 jaw adjustable chuck ($$$).
Then get or build a nice steady rest,taper attachment,5C Collet closer,5C collets,large diameter live center,clamp type knurl tool,aloris tool post,some good flip tip tooling and your all set!
AAA: I have a set-tru PBA 6-jaw that cost a bundle, I don't even want to guess what something is snazzy as the Cushman you're describing costs.
50 BMG Site:
www.hevanet.com/50shooter
www.hevanet.com/50shooter
DRO
I wish I had a DRO on my Bridgeport and Lathe .. Only thing I have a DRO on is my EDM...
a DRO on a bench mill .. you da man ..
We have them on all of the lathes at work and I don't realise how spoiled I am until I go out in the garage and have to setup 2" travel indicators for everything.
I keep looking on Ebay for them but keep getting out bid.
Nice to see other peoples shops...
a DRO on a bench mill .. you da man ..
We have them on all of the lathes at work and I don't realise how spoiled I am until I go out in the garage and have to setup 2" travel indicators for everything.
I keep looking on Ebay for them but keep getting out bid.
Nice to see other peoples shops...
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featherblue
- Silent But Deadly
- Posts: 325
- Joined: Thu Aug 28, 2008 4:56 pm
- Location: Crackerville, Northern Nevada
Another option is to get or make a set of soft jaws for the three jaw (scroll) chuck. Then bore these in the machine to your tube OD.
Soft jaws are cheap and available in steel and aluminum. We keep several sets around because they save time on setups.
Soft jaws are cheap and available in steel and aluminum. We keep several sets around because they save time on setups.
Do you love your country?
Will you fight to keep it?
If answers are yes, better be prepared . . .
Will you fight to keep it?
If answers are yes, better be prepared . . .
I moved my jaws around to every position imagineable and it go a little better not much.
Cut several pieces and my measured them all come out with less than a thou runout.
Mike, I'm going to be sending my bbl to you next week to get threaded. My only concern on my can is the end that is threaded that mounts to the bbl, that is why I'm being a little anal about my lathe runout. I aligned my centers when I got the lathe running, about .001 on a 16" piece of round stock, I'm ok with that.
Checked runout on spindle, chuck mount, every where I could get the indicator in and everything was .001 or less.
Four jaw is shipped, will see what I can do with that when it gets here. Not in a big hurry to screw things up. Thanks for the good tips and hints. Where be a good place to get soft jaws??
Cut several pieces and my measured them all come out with less than a thou runout.
Mike, I'm going to be sending my bbl to you next week to get threaded. My only concern on my can is the end that is threaded that mounts to the bbl, that is why I'm being a little anal about my lathe runout. I aligned my centers when I got the lathe running, about .001 on a 16" piece of round stock, I'm ok with that.
Checked runout on spindle, chuck mount, every where I could get the indicator in and everything was .001 or less.
Four jaw is shipped, will see what I can do with that when it gets here. Not in a big hurry to screw things up. Thanks for the good tips and hints. Where be a good place to get soft jaws??