Stuck chuck

Advert

New Replies

Report Bug

Help/FAQs

Stuck chuck

This topic has 27 replies, 14 voices, and was last updated 9 November 2010 at 09:11 by JimmieS.

Viewing 25 posts - 1 through 25 (of 28 total)

1 2 →

Author

Posts
2 November 2010 at 10:12 #5270
Mark Smith 3
Participant
@marksmith3
Advert

2 November 2010 at 10:12 #57988
Mark Smith 3
Participant
@marksmith3
I have recently bought a chinese copy of a Grizzly late mill combo ( I can hear the howls already). I know the are not ideal but it will suffice for my modest engineering needs. My problem is the chuck refuses to unscrew. I have put timber in the jaws only to have it shatter. I am afraid to hit too hard in case I damage the chuck or the spindle. Any suggestions would be welcome as I want to fit a four jaw at some point.

Mark
2 November 2010 at 10:49 #57990
Nicholas Farr
Participant
@nicholasfarr14254
Hi Mark, are you sure its the type that unscrews, or is it the sort that is fixed to a permanent backplate with socket head screws, or camlock.

Regards Nick.

Edited By Nicholas Farr on 02/11/2010 10:55:45
2 November 2010 at 12:54 #58000
Ian S C
Participant
@iansc
I think Nick is correct, and if they are socket head cap screws you might have to shorten the short leg of the Allen key to get between the backplate and the headstock. Ian S C
2 November 2010 at 17:05 #58006
Tony Pratt 1
Participant
@tonypratt1
Hi Mark, can you post a picture?

Tony
2 November 2010 at 18:06 #58009
Mark Smith 3
Participant
@marksmith3
Thanks Guys I hadn’t considered that as I didn’t know such beasts exist. Yes I will post a pick of the chuck. I have taken the mill off as I want to drive it from a separate motor; the dogs on the back of the bevel gear appear to be stripped as they are only nylon.

If it is the case as you suggest that the chuck is held on with screws there is little point in taking it off; I will just use my old lathe for four jaw work.

Mark
5 November 2010 at 04:58 #58188
Mark Smith 3
Participant
@marksmith3
You are right, the chuck is fixed to a permanent back plate with three socket screws. Would it be possible to make an adapter back plate with a spindle type thread to enable the fitting of standard Boxford 3 and 4 jaw chucks? I realise that the chucks will be a bit further from the head stock, but my old Barns lathe has a rather large overhang of the chuck as standard.

Mark

Edited By Mark Smith 3 on 05/11/2010 05:01:00
5 November 2010 at 10:41 #58199
Ian S C
Participant
@iansc
Mark, does the lathe have screw cutting facility, if so you could do it easily, if its like any similar machine to the ones I know its only about a 4″ chuck, and you proberbly don’t want to use much more than that. Ian S C
5 November 2010 at 14:46 #58216
Howard Jones
Participant
@howardjones35282
I also have a stuck chuck.

mine is a pratt-burnerd griptru.

it screws on to the mandrel ok. that aspect isnt stuck

to my knowledge it hasnt been apart in 20 to 25 years. whenever a solvent goes near it it oozes some black scroffulus gunk so I think it is high time it had a cleanout and a relube.

the back plate is held on with 3 socket head cap screws. I can remove these without too much difficulty. trouble is that I cant get the back plate off to get inside the chuck.

I know pretty well what is inside the chuck because I’ve had my ML7’s burnerd apart to see if it was worth keeping.

Could it be anything other than a simple press fit?

how would you get it apart without damaging it?

I’ve considered heating the front of the chuck with a hot air gun to try to expand it off.

….but I’m not quite sure what the geometry of the mechanism is.

I can feel some grot in the scroll as I tighten it and it needs constant centering to be true so it just has to get a clean out.

any better suggestions than my hot air gun?. hitting it with a plastic hammer achieved nothing.
5 November 2010 at 15:01 #58218
JDEng
Participant
@jdeng
Howard,

When you had removed the three capscrews which hold the chuck to the back-plate did you also slacken off and remove the three conical centering screws on the outside diameter of the chuck body? It’s a while since I stripped a Grip-Tru but from memory these three screws control the movement of the chuck body on the back-plate and are connected to both.

Make sure you mark the back-plate and the body so that they go back in the same relationaship.

John.
5 November 2010 at 15:06 #58219
Paul White 3
Participant
@paulwhite3
hello Howard,

I’ve been there, after a good time thinking I realised that the backplate is held to the front section by the adjusting screws (3off).They must be removed before attempting a separation of the chuck halves.

Good luck regards.
5 November 2010 at 15:11 #58221
NJH
Participant
@njh
Hi Howard

I have the mounting and operating instructions for a Griptru however they are too lengthy to post here (Four A4 pages) One point though it does state :-

” IMPORTANT – When dismantling the chuck for cleaning, the micro screws must be removed before attempting to remove the back half of the chuck. ”

These are great chucks and worth treating carefully – quite possible to adjust to .0002″ or better but not much change out of £500 for a new one!!

If you message me I can arrange to get a copy of the 4 pages to you

Regards

Norman
5 November 2010 at 16:16 #58224
KWIL
Participant
@kwil
Pratt-Burnerd recommend Molybdenum Disulphide grease for all chuck greasing, which is of course Black. Perhaps this is Howard’s “black scroffulus gunk”?
5 November 2010 at 16:34 #58225
Terryd
Participant
@terryd72465
Posted by Mark Smith 3 on 02/11/2010 10:12:38:

I have recently bought a chinese copy of a Grizzly late mill combo ( I can hear the howls already)………

Mark

Hi Mark,

Sorry to be the bearer of bad news, But the Grizzly machines are mostly of Chinese origins. So effectively the Grizzly is a copy of your Chinese lathe. What model Grizzly is yours equivalent to?

By the way, Chinese machines ain’t bad if you set ’em up right.

Terry
5 November 2010 at 17:40 #58226
Mark Smith 3
Participant
@marksmith3
Thanks, Ian and Terry. Yes, Ian, it is a screw cutting lathe, now I need to find some suitable steel to make an adapter plate. This should be interesting with my modest engineering skills, but I should learn a thing or two along the way.

Terry, the grizzly model my lathe looks like isG4015Z
6 November 2010 at 12:53 #58285
Terryd
Participant
@terryd72465
Hi mark,

It is a Chinese lathe The Grizzly that is) There is a good manual on the Grizzly site which may help you. Look Here.

Terry

Edited By Terryd on 06/11/2010 12:53:54
6 November 2010 at 16:12 #58293
Chris Trice
Participant
@christrice43267
NJH, I’d be very interested in your generous offer. I bought effectively a brand new Griptru that’s been sitting in the brown paper for years. You can find me at sfx_films @ ntlworld.com (remove gaps). Many thanks in advance.
6 November 2010 at 18:12 #58299
Mark Smith 3
Participant
@marksmith3
Thanks Terry that is brilliant. My Lathe must be a Grizzly as it is exactly the same. A manual is exactly what I want. Isn’t the web a wonderful thing.

Mark
7 November 2010 at 10:41 #58331
Terryd
Participant
@terryd72465
Hi Mark,

Glad to be of help,

Best regards

Terry

P.S. I wholeheartedly agree with you about the web.

T
7 November 2010 at 21:13 #58383
JimmieS
Participant
@jimmies
I have been given a 3 jaw chuck, the jaws of which are stuck half opened. Using the key without excessive force I can only move the jaws very slightly in either direction. I understand it was used for wood turning and assume the scroll has got clogged with dust. Any advice on how to cure this problem would be very much appreciate.

Jim
8 November 2010 at 09:38 #58413
Mark Smith 3
Participant
@marksmith3
Terry, thanks to you I have repaired the lathe drive. The manual showed a dog clutch that slides between the lathe drive and the mill drive. After some sweating and swearing I dismantled it and put it in my old lathe where a few turns with emery cloth cleaned and improved the clearance, now it works perfectly. The gear is not damaged as I first thought.

Apparently a four jaw chuck and adapter plate is available for this machine.

Jim, I think you have no choice but dismantle the chuck and clean it.

Mark
8 November 2010 at 19:02 #58448
JimmieS
Participant
@jimmies
Hi Mark

My problem is I can not move the jaws far enough to dismantle it. Any ideas?

Jim
8 November 2010 at 21:24 #58454
Keith Long
Participant
@keithlong89920
Hi Jim

I’d try giving it a soaking/flushing in a solvent like paraffin or white spirit combined with applying “gentle” pressure on the jaw screws as hopefully you get some of the rubbish loosened. You may find that have to take the jaws inwards rather than outwards at first but hopefully as you get the muck out you should find that you can get more movement and more effective washing.

Keith
8 November 2010 at 22:37 #58461
JimmieS
Participant
@jimmies
Hi Keith

Many thanks for your advice. Will give it a go.

Jim
8 November 2010 at 22:58 #58465
John Olsen
Participant
@johnolsen79199
Doesn’t there have to be some way to take things apart to get at the scroll? (You did say three jaw, this would not apply to an independent chuck of course.) If it is a conventional chuck I would have thought that the back plate would have screws holding it on, and by undoing those the scroll should be accessable through the back. If it is one of the smaller ones, like the lever operated Unimat ones, there is a circlip on the back around the boss that screws onto the mandrel nose. But for any three jaw self centreing chuck, there has to be some way in which the manufacturer installed the scroll. Drill chucks are pressed together and I suppose it is possible that someone has made a lathe chuck like that too.

But if it does prove impossible to get at the scroll from the back, then the soaking approach sounds like the best idea.

regards

John
Author

Posts