|188 forum posts|
I have an independent 4 jaw chuck sitting on my workbench not being used. It looks vintage and has no maker's name. The jaws "fit" and appear to be from a set (all marked 171) but I am unable to say if they are original.
The problem with this chuck is the jaws do not close parallel with each other. A superficial glance suggests bell-mouthing through wear but on closer inspection the inner faces of the chuck jaws show they are in excellent condition - they still show the original machining.
The "slides" in the chuck body look good as do the screws. The jaws have minimal slop in their respective slides.
I could make a ring to hold all 4 jaws in position and then grind their internal faces. I have previously done this with a 3 jaw scroll chuck but never needed nor thought I would need to do this with an independent chuck.
Any suggestions before I attempt a fix?
|188 forum posts|
Another thing I should mention is the jaws are numbered 1, 2, 3 and 4. The chuck is similarly marked with centre-punched dots.
|Oily Rag||14/04/2021 10:28:06|
416 forum posts
Do(es) the slotted screw(s) in the face just attach the rear adaptor plate or is the body of the chuck a 2 piece construction? If it is two piece, will it allow you to strip it out and measure the accuracy of the jaw tenons.
Looks like it has had a component held in the very end of the jaws and been over tightened (with a pipe on the chuck handle?). Common problem with unskilled operators attempting to 'true' work up.
|Michael Gilligan||14/04/2021 10:31:51|
18080 forum posts
I wonder if it has been previously used for holding short insertion-lengths very tightly
... is it possible that just the first ’step’ is distorted ?
Edit: Martin beat me to it
Edited By Michael Gilligan on 14/04/2021 10:32:39
20637 forum posts
Just because the inner face of the jaws are in god nick does not mean it has not had a hard life, could well have done a lot of work with the jaws the other way round, nicks in the face of the jaws confirm that and worn the slots.
It all looks very worn, rounded and pitted, the "machine marks" could even be where someone else has had a go at it rather than being original which would probably have been ground anyway
|larry phelan 1||14/04/2021 12:24:45|
|1031 forum posts|
4 jaw independent chuck, or self centring chuck ?
5505 forum posts
The jaws, and body, could be distorted rather than worn, ie bent. To regrind using the usual clover-leaf plate could be fiddly with independent jaws, trying to get them all in exact alignment. Much easier on a self-centreing 3-jaw. So a common alternative is to regrind them square on a surface grinder with jaws clamped to a suitable angle plate etc. But could be done in the lathe with some fiddling. I suppose you don't have to do them all together like a three jaw. You could do them one at a time.
Ive done it with a couple of equally ancient and abused looking three jaws and very happy with the result.
Edited By Hopper on 14/04/2021 13:11:36
|Roger Best||14/04/2021 14:11:57|
|243 forum posts|
Strip it down and get a square onto those jaws, you can't fix what you can't measure.
I suspect that they will need re-machining, the best method will depend on what you have access to.
|Michael Gilligan||14/04/2021 14:16:18|
18080 forum posts
|Pete Rimmer||14/04/2021 19:43:39|
|979 forum posts|
Take the jaws out and lat the chuck face down on a surface plate. I bet it will rock like a boat.
More often than not bell-mouthed jaws is actually bent chuck face IMO.
|Dave Halford||14/04/2021 19:53:23|
|1507 forum posts|
I had one like that, more commonly known as a door stop.
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.