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Stuck Chuck

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Steve Crow06/01/2020 17:38:37
244 forum posts
108 photos

Here are some pictures of my 4 jaw chuck with a rotary table adaptor.

chuck1.jpg

chuck2.jpg

I've never had a problem before but somehow the adaptor has become stuck in the chuck.

I tried holding the adaptor in brass jaws in the vice and turning the chuck but I couldn't get the vice tight enough to grip.

Next I got the biggest, baddest screwdriver and ground the end to fit the slot exactly, put the chuck in the vice - didn't budge.

Even with mole grips on the screwdriver - same result.

chuck3.jpg

I thought of locking nuts on the spindle and turning it off with a spanner but there is just enough thread for one full nut never mind two.

I would rather not damage the adaptor but will if I have to.

Anyone got any ideas?

Cheers

Steve

pgk pgk06/01/2020 17:46:57
1968 forum posts
288 photos

It's not one of those datt things where it happens to have a L hand thread and you've forgotten?

Other obvious options heat or freeze to hope some differential expansion loosens it? A tap on the bottom? Soak the whole thing in penerating oil overnight? Make up a T-handled driver for even more purchase?

pgk

old mart06/01/2020 17:48:10
2193 forum posts
164 photos

Have you got an impact driver, the kind with the 1/2" square drive? Mine has an adaptor which takes flat screwdriver bits up to 1/2" wide.

 

https://www.ebay.co.uk/itm/Kennedy-15-PCE-Impact-Driver-Set-1-2-SQ-DR/112730741550?_trkparms=ispr%3D1&hash=item1a3f469b2e:g:K7oAAOSwkWddgmZF&enc=AQAEAAACQBPxNw%2BVj6nta7CKEs3N0qV88O3O6t24xJzsxyj438jwJM5r6gl2FLday8qB0ZdZkXymx9VMolMoEOj35xGDCfopILu0UTkgMzzSHxCQN5dp6wVK%2BF6qlzi4UG7gyrnL02s8RAU5njp11EtK17CcnT0YyuAhpr317QkSoLefsqRuXkUOSkbugIIq%2BXvXTj7Vr7YAUfP4L3A%2FOXk%2FnISEamK%2FSmyc3IMtJXVO%2BJRCOdO14lNUBWPkpaigLZIr0jx%2B%2Fdf7Fv5Ou3ldDJpjMhHi%2BhT4NpoiVeBPN699KJuLbvmWmzujE1A2QmryHcE8hVkDJFn6kxdVFp1%2FF6SyQBaZy%2Fe2giHOF8QqNkyr%2Fc34boPKeX0o5lVNp4e7SyTDvWfYS6AMOMC%2FTNhU7n1fQGbT1dgQbmtJUQE3PKM8PDQboxaxBJpBseEfxzKLLZP6aCO7hyuSgwUwOxjQ7Kkr8umsAz4Xhp6b5pZWx61%2Ba%2B8tO0RDwNcXRfgbkcbr0Zi0WC9LKcnXE6%2BMpK9R2xDJ%2F73jVbgzVMvUILIx1AYmgDmaZewlj8U1wYPTUCjeqqY6Tbagl%2FkKhLr4zI4BGS48o5l%2F0Y7yYVFfpsQe4m7hhXQlyJwUvGF5vHLqc1NDg0zPYElsw5%2Fx6EGrAXYATC3bEr9kN0K7WkEbePZPribiamqjg8j8eZRJ7L9DIeDr0rLczJYRDPGXx3F%2F2TfODi8o0as2iKk%2FHwEr2OHxIFv4eKSf5uP11aqrGuhBPFHuEp5hQaDWQw%3D%3D&checksum=112730741550f8563f1753b0446792ca5b271601950c&enc=AQAEAAACQBPxNw%2BVj6nta7CKEs3N0qV88O3O6t24xJzsxyj438jwJM5r6gl2FLday8qB0ZdZkXymx9VMolMoEOj35xGDCfopILu0UTkgMzzSHxCQN5dp6wVK%2BF6qlzi4UG7gyrnL02s8RAU5njp11EtK17CcnT0YyuAhpr317QkSoLefsqRuXkUOSkbugIIq%2BXvXTj7Vr7YAUfP4L3A%2FOXk%2FnISEamK%2FSmyc3IMtJXVO%2BJRCOdO14lNUBWPkpaigLZIr0jx%2B%2Fdf7Fv5Ou3ldDJpjMhHi%2BhT4NpoiVeBPN699KJuLbvmWmzujE1A2QmryHcE8hVkDJFn6kxdVFp1%2FF6SyQBaZy%2Fe2giHOF8QqNkyr%2Fc34boPKeX0o5lVNp4e7SyTDvWfYS6AMOMC%2FTNhU7n1fQGbT1dgQbmtJUQE3PKM8PDQboxaxBJpBseEfxzKLLZP6aCO7hyuSgwUwOxjQ7Kkr8umsAz4Xhp6b5pZWx61%2Ba%2B8tO0RDwNcXRfgbkcbr0Zi0WC9LKcnXE6%2BMpK9R2xDJ%2F73jVbgzVMvUILIx1AYmgDmaZewlj8U1wYPTUCjeqqY6Tbagl%2FkKhLr4zI4BGS48o5l%2F0Y7yYVFfpsQe4m7hhXQlyJwUvGF5vHLqc1NDg0zPYElsw5%2Fx6EGrAXYATC3bEr9kN0K7WkEbePZPribiamqjg8j8eZRJ7L9DIeDr0rLczJYRDPGXx3F%2F2TfODi8o0as2iKk%2FHwEr2OHxIFv4eKSf5uP11aqrGuhBPFHuEp5hQaDWQw%3D%3D&checksum=112730741550f8563f1753b0446792ca5b271601950c

Edited By old mart on 06/01/2020 17:57:03

Edited By old mart on 06/01/2020 17:58:12

Mick B106/01/2020 18:09:56
1767 forum posts
91 photos

Maybe you need an even bigger, badder screwdriver with a shorter shank, or an adjustable spanner on a piece of steel flat ground to fit the slot over its full width or near ?

Howard Lewis06/01/2020 18:12:13
3757 forum posts
3 photos

Even better if you could hold a hexagon shank screwdriver bit (Make one? ) in a socket in an air Impact gun. It might eventually hammer loose.

Once separated, begins the hunt for WHY?

Followed by the means to prevent a repeat!

Howard

DiogenesII06/01/2020 18:13:36
146 forum posts
56 photos

Old Mart got there first +1 for impact driver.

duncan webster06/01/2020 18:22:33
avatar
2839 forum posts
43 photos

Try warming the chuck before you get too violent. If you've got a nut that fits the thread saw though half way on a point, so that when you put it in the vice the nut will close up on the thread, that will help to prevent damage to the thread, and the mass of the vice will tend to keep the threaded bit cool.

Steve Crow06/01/2020 19:12:55
244 forum posts
108 photos

Thank you all.

I like the impact driver idea (already considered it) but I'm reluctant to buy a set for a one off job.

I only have a kitchen table workshop and limited workshop time so I don't want to get bogged down with making a tool for a one off job.

I really like Duncan's split nut suggestion. I don't have any nuts to fit but the thread in question is 3/8 UNC. Brass manifold nuts are readily available in this size. These seem to be a bit longer and thicker than standard nuts and might provide a bit more grip on the thread. But maybe brass nuts would be less friction than steel on steel? Any observations welcome.

Alternatively, I can squeeze on a half nut and 2/3 of another half nut and try the locked nut method?

At the end of the day, a new adaptor is about £10 so destructive options are not the end of the world.

not done it yet06/01/2020 19:56:21
5124 forum posts
20 photos

The structure of the part would be good. If you are trying to loosen the chuck, while being clamped on both sides will need considerable force - and it may just slip at that point.

If the screw inside the chuck is simply threaded into the rear piece, they did not make that slot that length for no good reason!

Make a wide blade to fit the whole length of the slot and then apply a turning force - in the correct direction. Two adjustables would suffice. Preferably one being of the ‘mole wrench’ type. Securing the chuck in a vise is likely better than holding the rear thread until loosened.

Ian P06/01/2020 21:03:38
avatar
2437 forum posts
101 photos

I am not familiar with Sherline lathes but it seems odd that its mandrel has a 3/8" UNC internal thread rather than the conventional male thread and register for the chuck/faceplate etc.

In any event does the screw with a slotted head actually have a shoulder at some point or does it just like a large grub screw that converts the UNC to the chuck thread?

I know the above does not solve the problem, but AIUI (or dont understand it) what it the screw stuck against?

Ian P

I missed the rotary table mention. Still not sure if there are two different threads on the adapter thing

Edited By Ian P on 06/01/2020 21:07:15

stephen goodbody06/01/2020 21:21:56
56 forum posts
40 photos

Hi there,

Are you are able to drill a hole for a 'tommy bar' into the side of the adapter, say 5/16" dia x 1" deep?

If so then, by removing two of the chuck's jaws, you should be able to grip the chuck in a bench vice using the remaining chuck jaws (the front face of the chuck will be lying flat on the top of the vice). Then insert a bar - an Allen Key may do - in the drilled hole and clout the bar (gently at first) to remove the adapter.

Good luck,

Steve

JohnF06/01/2020 22:56:12
avatar
1026 forum posts
143 photos

Steve, not sure just what kit you have available, access to a pillar drill would be useful but you do say it is on a rotary table fitting so assume you have a small mill which may suffice ?

Anyway what I would try is first make a screwdriver from an allen key then with this in the pillar drill chuck use a split nut to grip the screwed adaptor in your well tightened vice and using the drill quill to apply downward pressure to the screwdriver thus preventing it slipping out of the slot and armed with a spanner you should be able to release the screw - providing the thread/nut do not slip.

Good luck John

Michael Gilligan06/01/2020 23:27:35
avatar
16620 forum posts
723 photos
Posted by Ian P on 06/01/2020 21:03:38:

I am not familiar with Sherline lathes but it seems odd that its mandrel has a 3/8" UNC internal thread rather than the conventional male thread and register for the chuck/faceplate etc.

In any event does the screw with a slotted head actually have a shoulder at some point or does it just like a large grub screw that converts the UNC to the chuck thread?

I know the above does not solve the problem, but AIUI (or dont understand it) what it the screw stuck against?

Ian P

I missed the rotary table mention. Still not sure if there are two different threads on the adapter thing

Edited By Ian P on 06/01/2020 21:07:15

.

This should make it clearer, Ian : **LINK**

https://www.sherline.com/product/chuck-adapters-rotary-table/

MichaelG.

Bandersnatch07/01/2020 01:44:58
avatar
1719 forum posts
60 photos
Posted by Steve Crow on 06/01/2020 19:12:55:

I like the impact driver idea (already considered it) but I'm reluctant to buy a set for a one off job.

That's how I built up my workshop tool collection .... they all started as "one-off jobs".

Ian P07/01/2020 08:48:55
avatar
2437 forum posts
101 photos

Thanks Michael, your link shows what that the adapter larger diameter thread fits the chuck body.

I now assume that the chuck thread has a shoulder or restriction (where the thread runs into the smaller tapping diameter) otherwise the adapter would pass right through the chuck body. If not what is it jammed against?

Ian P

Michael Gilligan07/01/2020 10:42:22
avatar
16620 forum posts
723 photos
Posted by Ian P on 07/01/2020 08:48:55:

[…]

If not what is it jammed against?

.

Just ‘thinking aloud’ here, because I am not sure of the constructional details ... but:

Two screw threads of the same hand, but different pitches, can act together to form a very fine-pitch combination.

... the adjuster used on Norris planes being an example.

In the case of two relatively large diameter discs [the chuck and the plate] being screwed together by such threads, the clamping force and friction could be enormous.

MichaelG.

JohnF07/01/2020 10:47:14
avatar
1026 forum posts
143 photos
Posted by JohnF on 06/01/2020 22:56:12:

Steve, not sure just what kit you have available, access to a pillar drill would be useful but you do say it is on a rotary table fitting so assume you have a small mill which may suffice ?

Anyway what I would try is first make a screwdriver from an allen key then with this in the pillar drill chuck use a split nut to grip the screwed adaptor in your well tightened vice and using the drill quill to apply downward pressure to the screwdriver thus preventing it slipping out of the slot and armed with a spanner you should be able to release the screw - providing the thread/nut do not slip.

Good luck John

Thanks MichaelG that shows the system used so regarding my post please ignore the section shown above relating to the split nut ! I had assumed the adaptor was a two piece arrangement ! I have used the drill press arrangement to remove VERY tight slowed screws with great success and no marring of the screw head/slot.

John

edit - you will of course have to clamp the chuck body to the table

Edited By JohnF on 07/01/2020 10:48:45

Michael Gilligan07/01/2020 11:12:24
avatar
16620 forum posts
723 photos
Posted by Steve Crow on 06/01/2020 17:38:37:

Here are some pictures of my 4 jaw chuck with a rotary table adaptor.

chuck1.jpg

chuck2.jpg

I've never had a problem before but somehow the adaptor has become stuck in the chuck.

[…]

.

dont know ... My ‘differential thread’ idea is probably dead

From the ‘Adapters’ page, I quote “The adapter screws into the 3/8-16 threaded center hole of the table.”

And Steve’s chuck is clearly marked 3/4-16 ... so they’re the same pitch blush

MichaelG.

.

Edit: I presume this to be the chuck in question:

https://www.sherline.com/product/4-jaw-independent-chuck/#instructions

Edited By Michael Gilligan on 07/01/2020 11:15:54

Neil Wyatt07/01/2020 11:21:53
avatar
Moderator
18316 forum posts
718 photos
77 articles
Posted by old mart on 06/01/2020 17:48:10:

Have you got an impact driver, the kind with the 1/2" square drive? Mine has an adaptor which takes flat screwdriver bits up to 1/2" wide.

**LINK**

Edited By old mart on 06/01/2020 17:58:12

You can delete everything after and including the question mark. If you don't, every time someone clicks then it is sending a comprehensive little chunk of out of date information ("trkparms=" short for "tracking parameters" about you and your browsing history to eBay.

Neil

Ian P07/01/2020 11:25:08
avatar
2437 forum posts
101 photos

I would still like to know why a headless screw can jam in the parallel (through?) thread of the chuck.

Ian P

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