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Stuck chuck

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Mark Smith 302/11/2010 10:12:38
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175 forum posts
36 photos
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
Nicholas Farr02/11/2010 10:49:06
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3988 forum posts
1799 photos
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

Ian S C02/11/2010 12:54:35
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7468 forum posts
230 photos
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
Tony Pratt 102/11/2010 17:05:05
2319 forum posts
13 photos
Hi Mark, can you post a picture?
Tony
Mark Smith 302/11/2010 18:06:03
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175 forum posts
36 photos
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
Mark Smith 305/11/2010 04:58:42
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175 forum posts
36 photos
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

Ian S C05/11/2010 10:41:22
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7468 forum posts
230 photos
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
Howard Jones05/11/2010 14:46:05
70 forum posts
112 photos
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.
JDEng05/11/2010 15:01:25
27 forum posts
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.
Paul White 305/11/2010 15:06:46
109 forum posts
23 photos
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.
NJH05/11/2010 15:11:04
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2314 forum posts
139 photos
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 
KWIL05/11/2010 16:16:20
3681 forum posts
70 photos
Pratt-Burnerd recommend Molybdenum Disulphide grease for all chuck greasing, which is of course Black. Perhaps this is Howard's "black scroffulus gunk"?
Terryd05/11/2010 16:34:17
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1946 forum posts
179 photos
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
Mark Smith 305/11/2010 17:40:34
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175 forum posts
36 photos
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
Terryd06/11/2010 12:53:14
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1946 forum posts
179 photos
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

Chris Trice06/11/2010 16:12:53
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1376 forum posts
10 photos
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.
Mark Smith 306/11/2010 18:12:50
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175 forum posts
36 photos
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
Terryd07/11/2010 10:41:22
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1946 forum posts
179 photos
Hi Mark,
 
Glad to be of help,
 
Best regards
 
Terry
 
P.S. I wholeheartedly agree with you about the web.
 
T
JimmieS07/11/2010 21:13:41
310 forum posts
1 photos
 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
Mark Smith 308/11/2010 09:38:54
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175 forum posts
36 photos
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
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