Chuck binding

I have a second hand CJ18 which has seen better days. one jaw of the four jaw independent is 'sticky' and I have to work hard to centre the pieces. I have dismantled it as far as I can, cleaned it in de-greaser, greased it and it still sticks.

I can only get as far as removing the jaws and can't see a way to dismantle any further. Is there anything else I can do short of buying a replacement chuck?

I can't see a makers name but:-

Have you tried exchanging the sticky jaw with one of the others, to see if the sticking is down to the jaw or the slot? That at least would tell you the area to look for a fault.

Maurice.

Jaws and slots are often numbered to keep matched items together.

Sounds like one of the jaws is either too tight against the slot or the mating thread. Not sure how it could be fixed but I have a similar problem on a larger four jaw.

Michael W

Just had exactly that with one of a set of soft jaws for my 3 jaw griptru.

Ran the jaw a couple of times in the chuck and the held up to the light to see what part was most polished.

There was a burr on some of the thread edges and also on the groove where it locates in the chuck.

A gentle stoning of the groove, and a rub on some fine wet and dry on a glass plate cured it nicely.

Bill

I would check very carefully for any burrs or bruising on the jaw and its slot, does the screw turn freely with the jaw removed from the slot? I recently bought a 4 jaw self centering chuck which was rather stiff to operate, after a light rub round the slots with a needle file it now moves quite easily and smoothly, we are not talking about removing any serious amount of material here just a very light dressing to clear any burrs or roughness from machining. I think a lot of products are supplied as machined but I think a good machinist should clean all sharp edges to make things more comfortable to handle and stop burrs from compromising the fit of mating parts, this is a job that gets skipped to keep costs down.

Mike

I see Bill posted while I was composing, we seem to be thinking along the same lines.

Edited By Mike Poole on 27/02/2017 16:04:53

The screw might be damaged. Pull the screw retainer out the back of the chuck. Then slide out the screw and inspect it. With the screw out you can determine if the jaw itself is binding. If it is a binding jaw, stone off the high spots.

Often, deburring, (or even slightly relieving the sticky one) the slots in the chuck body will bring about a big improvement. There may even be some bright spots to tell you where to direct your activities.

Howard

The screws are often retained by a plug with a fork in the end to retain the screw, it can be carefully pressed or tapped out with a soft punch. The body is most likely cast iron so the needle file will be effective but the jaws should be hard so a stone or fine abrasive will be required.

Mike

When I've this problem it's always been swarf trapped. Clean out, look for bits of metal imbedded in screw, pick out with a scriber or similar.

Thank you for your replies, I have tried changing the jaws over even 'though they are numbered, it made no difference other than confirming it seems to be the slot. I have dismantled as far as I can again today and for a while the problem seemed to be worse as the jaw seized 14 way in! Taking it out put things back to 'Normal' i.e. binding.

I could see no obvious binding spots on any of the jaws nor anything 'untoward' (to my untrained eye) down the slots.

The worm/screw in the difficult slot is very loose, I surmise that the two part thread on this screw (in which the key fits) has some sort of retaining lug half way down the slot.

I can't see how to get the plug (4 in No. corresponding to the jaws) at the rear of the chuck, out there doesn't appear to be a way.

Thanks again guys, all help gratefully accepted.

To do properly the chuck has to be stripped.

However, you can degrease both jaw and slot once again. Lightly Engineers blue the jaw and see if you can see any obvious areas of rub when you wind it in and out. If its visible a light scrape in the chuck slot may just ease it.

You should me able to see the ends of the fork that the screw is retained by and punch it out with a soft metal drift, it will help to dot mark the position of the plug to assist reassembly.

Mike

"I can't see how to get the plug (4 in No. corresponding to the jaws) at the rear of the chuck, out there doesn't appear to be a way."

See Mike Poole's post above at 16:13:35

Take the jaw out, you will see the screw rests in a fork which is part of the "plug", The only way to get it out is to drive it out using a drift or punch on the end of the fork, or it may be possible to get a narrow punch down beside the fork to bear on the main part.

Its a long time since I had to dismantle one; sometimes they just won't give, but as yours looks clean and non-rusty it may be ok

Thank you all, job for tomorrow.

Worth putting a bit of effort into, a tight chuck is unpleasant to use to say the least. Strip, clean, dress the jaws and slots so you can slide the jaws along with finger pressure, not sloppy but not tight either, refit screws and jaws, check they don't bind anywhere, correct it if they do. Lightly lubricate and reassemble. A couple of hours work can transform a piece of junk into a chuck that's a joy to use. Sometimes, a good clean is all it needs. Dave

I took the chuck apart again and noticed that part of the worm drive was brokef off for about eighty degrees of the circle.

Amadeal sent me a new chuck in 24 hours as that seemed the only solution.

Thank you all again for you help.

John