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View Full Version : Fixing my 3 jaw chuck with a reamer ?



TR
12-08-2010, 07:58 PM
So my new expensive 3 jaw d1-4 chuck has a TIR of 0.30mm. The jaws are hardend. What if I try and correct the runout by using a reamer. Reamer goes in the tail stock, spin up the chuck and slowly ream. Stupid idea ? Any suggestions ?

PeteM
12-08-2010, 08:11 PM
Good way to ruin a reamer. Bad way to reduce runout in a chuck.

First thing to do is check the runout at several different diameters of stock. Make sure the jaws are clean and free of burrs when you do this. Check using perfectly round stock. The scroll will always vary a bit.

Various sources of runout include the mounting, the scroll, and the jaws. You're not going to do much about a bad scroll (big differences in runout and location at different diameters) beyond returning the chuck.

If it's out the same at every diameter, or even just the diameter you do most of your work at, it might be either the mounting or the jaws. If your chuck body has a lot of TIR, it might be the mounting. This is corrected by opening up the bolt holes between mounting plate and chuck a bit, plus the recess, and carefully nudging things back in place to get near zero TIR at a diameter you commonly turn at. Then tighten it all up, checking the indicator as you go. You've basically made your chuck a really inconvenient "Adjust-Tru" or maybe "Adjust-once-and-check-now-and-then" in this process.

If it's the jaws, they can be ground in place. Probably other threads on that if you do a search.

A.K. Boomer
12-08-2010, 08:12 PM
First off you need to verify its not in the scroll --- try a 1/4" piece of stock - a 1/2" a 1" and so on and mark the chuck where the deviation takes place on the low or high side,,,
if consistent then you might try something to true it up but a reamer is not the tool for the job as the three jaw is an interruption that would reek havoc with the reamer flutes,

Rig a little dremmel grinder and also keep in mind the jaws have to be loaded with something and kept under pressure during the grind --- its a hat trick as you have to load the jaws exactly where needed to be ground, someone might chime in with a how too - if not I'll try to post in the monyatta...

macona
12-08-2010, 08:12 PM
Ohhh... Baaadddd idea.

Unless you like ruined chuck jaws and pieces of reamers flying towards you.

macona
12-08-2010, 08:14 PM
This is the way to do it:

http://i65.photobucket.com/albums/h228/macona/Monarch%2010EE/DSC03790.jpg

http://i65.photobucket.com/albums/h228/macona/Monarch%2010EE/DSC03795.jpg

rklopp
12-08-2010, 08:26 PM
I've trued Pratt-Burnerd jaws using a carbid boring bar. The jaws are not that hard. Just keep the RPMs low and use decent feed but light depth of cut. Be sure to preload the jaws somehow.

The Artful Bodger
12-08-2010, 08:28 PM
TR, if the chuck is new I would be wary of grinding the jaws, and I am sure a reamer would be a disaster, until all other causes have been eliminated.

I am a fairly raw newbee and I dont even know the TIR on my chuck so I assume there is some and work accordingly, when using the three jaw and concentricity is important I try to do all the processes without removing from the chuck. If it is a new piece I try to plan the job so that the last action is to cut the part from the stub of scrap that stays in the chuck. From what I can gather this is the best way to handle inaccuracies in a 3 jaw.

Otherwise, for instance making changes to an existing part, I use my 4 jaw (while thinking how nice it would be to have two lathes so I did not have to heave the heavy chuck around).

John

J Tiers
12-08-2010, 09:12 PM
No idea if your chuck can benefit... the newer the chuck the less I'd think so.

I'd reserve grinding for a chuck that is bell-mouthed.... but you must suit yourself.

Here is how I have done it. I use a dremel or toolpost grinder to do the actual grinding. Depends what is available at the time. You need to "spark out" really well. Idea is from Rich Carlstedt.

http://img.photobucket.com/albums/0803/jstanley/chuckgrind.jpg

Drill some holes in the jaws with a carbide drill, and set the ring.... puts a load on the chuck virtually identical to actual clamping load.

A.K. Boomer
12-08-2010, 10:19 PM
That's thinkin, good Idea JT and Rich, and nice jig Macona...

vpt
12-09-2010, 08:21 AM
Just did mine as well not long ago. I should have dressed the stone first but it came out fine anyhow.

http://img258.imageshack.us/img258/8301/jawgrind002.jpg

http://img413.imageshack.us/img413/9627/jawgrind001.jpg

http://img340.imageshack.us/img340/5387/jawgrind003.jpg

moe1942
12-09-2010, 08:42 AM
How do you know it is your chuck causing run out??

RKW
12-09-2010, 10:49 AM
Grinding is the best (and only?) way to remove material that is hardened to any degree of precision. It would most certainly ruin any reamer.

But isn't it nearly pointless to try to get the perfect 3-jaw? That's the real reason for the 4-jaw anyway so that existing material/parts can be centered as-needed.

vpt
12-09-2010, 12:38 PM
Some like thier most used 3 jaw chuck to be as close as it can be.

Another thing to check is what the runout differences are using each keyhole. My 3 jaw has three keyholes and I found using the one marked 0 had the least amount of runout at least for that one size stock.

topct
12-09-2010, 04:57 PM
A three jaw chuck should never be tightened onto the work piece using one keyhole.

I was taught to start with just a snug on the first hole I put the key into and then tighten a little more at the next hole and continuing on around the chuck.

macona
12-09-2010, 06:10 PM
Grinding is the best (and only?) way to remove material that is hardened to any degree of precision. It would most certainly ruin any reamer.

But isn't it nearly pointless to try to get the perfect 3-jaw? That's the real reason for the 4-jaw anyway so that existing material/parts can be centered as-needed.

I virtually never use the 4 jaw, only when I need to hold something square. Otherwise its a 6 jaw adjust tru. But then that is virtually a 4 jaw adjustment wise but I have found that it holds concentric well over the range.

TR
12-09-2010, 06:22 PM
I contacted the manufacture. Positive response. They want me to run some checks on my spindle. I will do so tonight. My measured run out with a precision test bar is 0.02330 inches. Run out should be 0.0002 inches on this chuck.

challenger
12-09-2010, 08:53 PM
I have a question, if I may, about the desired outcome. My lathe has a L0 3-jaw chuck and the removable jaws are not in line with the fixed jaws. Is this common? It is on my ancient Sheldon EXL and it came with the lathe when I bought it 10+ years ago. If i slide a bar into the chuck it will stop at the fixed jaws after clearing the removable jaws. I would guess the removable set is maybe .05 larger than the fixed set. These are not soft jaws. The are reversible and look identical to the ones in the photo. Any advice on if I should be concerned and if so would I have to grind them and have the stone penetrate from the outside of the removable set through to the fixed set?
Thanks
Howard
Hampstead, NC

J Tiers
12-09-2010, 08:59 PM
A three jaw chuck should never be tightened onto the work piece using one keyhole.

I was taught to start with just a snug on the first hole I put the key into and then tighten a little more at the next hole and continuing on around the chuck.

Well, on both of mine, I suppose I could tighten it, then spin it a full turn and tighten the ONE pinion again.......

Not all chucks have multiple pinions.

A.K. Boomer
12-09-2010, 10:44 PM
If its a single then its a single and that's all you can do but I do agree with Toptc about distributing the load on the pinons and therefore centering the internals of the chuck, its not only an "every little bit helps"
It's a great way to achieve maximum torque for larger parts that you don't want coming loose.

huntinguy
12-09-2010, 11:09 PM
just for kicks and grins. Mount it in each of the three positions and see if that makes a diffrence.

Clean and clean again before each mounting.

J Tiers
12-09-2010, 11:23 PM
If its a single then its a single and that's all you can do but I do agree with Toptc about distributing the load on the pinons and therefore centering the internals of the chuck, its not only an "every little bit helps"


At least one of the chucks in question is an older Buck adjust-tru. Lots of good chucks don't have three pinions, it isn't necessarily a "second best" system.

gwilson
12-09-2010, 11:47 PM
I also stuff paper towels into the chuck just beyond where the grinding stops,to keep abrasive dust out of the chuck.

Juergenwt
12-10-2010, 01:23 AM
J Tiers- if you have to do it-that is the right way.
Macone- if you did not pre-load it's no good. Hard to see on the picture.

vpt
12-10-2010, 08:48 AM
A three jaw chuck should never be tightened onto the work piece using one keyhole.

I was taught to start with just a snug on the first hole I put the key into and then tighten a little more at the next hole and continuing on around the chuck.



I do that with drill chucks but never felt the need with the lathe chuck. I normally only use the one keyhole now because I know that is the one that is most accurate.

One of the reasons I think I don't feel the need for it is my little 10" atlas doesn't have enough power to tear work out of chucks. I have my motor belt set up to lift the motor and slip the belt under excessive load before other worse stuff would happen.

Mcgyver
12-10-2010, 10:26 AM
I contacted the manufacture. Positive response. They want me to run some checks on my spindle. I will do so tonight. My measured run out with a precision test bar is 0.02330 inches. Run out should be 0.0002 inches on this chuck.

:confused:

you've got a 3 jaw supposed to be good to 2 tenths - what make/model?

TR
12-10-2010, 12:16 PM
Good news no measurably spindle runout.

http://i663.photobucket.com/albums/uu354/topari/DSCN3732Medium.jpg

http://i663.photobucket.com/albums/uu354/topari/DSCN3730Medium.jpg

http://i663.photobucket.com/albums/uu354/topari/DSCN3729Medium.jpg

http://i663.photobucket.com/albums/uu354/topari/DSCN3728Medium.jpg

gwilson
12-10-2010, 01:15 PM
Try another test bar. It is surprising how many nicely ground objects aren't really true. Plus,you are testing a fair distance from the chuck. I generally use the ground end of an end mill to test a chuck. I have bars that look good,like the one in your picture,but they just aren't perfectly round or straight,somehow.

macona
12-10-2010, 01:17 PM
You are measuring wrong. You need to measure off the taper of the nose and the ground internal taper of the spindle nose. Thats where it matters (This is coming from the service manager from Monarch) The front flat has nothing to do with anything and the main flat has more significance.

But is your chuck mounted correctly? Can you fit a shim between the chuck and the back face of the camlock when it is secure?

Get yourself a DTI. The plunger indicators are only so useful. I have not used one in a very long time. Also use the balled tip.

macona
12-10-2010, 01:27 PM
J Tiers- if you have to do it-that is the right way.
Macone- if you did not pre-load it's no good. Hard to see on the picture.

You can see the ring for preload in the back of the jaws on the 6 jaw and on the master jaws on the 3 jaw.

I also took the shop vac and connected it to the other end of the spindle so dust was sucked away from the ways out the back. Worked real well.

Juergenwt
12-10-2010, 01:43 PM
Thank you Macona. I did forget one very important step.After re-grinding you should take out the jaws, clamp each one separately in a precision too makers vise or against an angle plate. Indicate the lowest point of the ground radius. Than grind out the radius until you hit the bottom of the radius and end up with a flat surface on the jaw. Use your indicator. You could set it to a planer gauge. Unless you do this you will end up with a ground radius on the jaw that will clamp true as long as the dia you are clamping is smaller or the same size as the ground dia. If the clamped dia is larger than the ground dia you will run into a problem because you are now holding your part with the sharp edge of the radius ground on the jaw. It will get bad real fast. Bin there-done that. Juergen