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4-jaw chuck jaws....

My four jaw works well, but......

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Bob Stevenson29/04/2020 20:20:08
579 forum posts
7 photos

When I aquired my little WM180 a couple of years back I was quite well pleased as it's a nice little machine and ideal for my clock-making exploits. For the money it was very good in most areas and came with two decent chucks among other items......

The 4-jaw is well done, neat, accurate and nice to use apart from the over vicious bite of the jaws. During the last two years I have steadily gained a draw full of bits of copper pipe and slips of drink can to protect work pieces which otherwise are always damaged by even light jaw pressure. Many times I have been tempted to remove the jaws and smooth off the sharp corners on the grindstone but have always failed at the last moment!...not really sure why!

Clearly I need 'soft jaws' but before I get to work, does anyone have any very clever tips, ideas, designs or other thoughts that would help to make the thing more workpiece friendly?

Clive Brown 129/04/2020 20:55:46
807 forum posts
39 photos

I think you are right to be cautious about putting the jaws to a grinding wheel, but a light "stoning" by hand might remove possible burrs on the gripping face of the jaws.

Apart from this, a supply of small brass packing pieces is useful but a difficulty with using these is that they fall out very readily whilst adjusting the chuck one jaw at a time. An improvement is to make a second chuck-key so 2 opposite jaws can be moved together thus avoiding the packing falling out. This also greatly speeds up centering of the work. This key doesn't have to be very robust.

BTW, soft jaws are usually for self-centering scroll chucks.

Edited By Clive Brown 1 on 29/04/2020 20:57:27

Bob Stevenson29/04/2020 21:18:32
579 forum posts
7 photos

Yes, 'soft' jaws are pretty much self defeating on a 4-jaw. I am considering cutting channels both sides of the jaws to take copper shims with the edges pushed into the channels,....but, someone here may have a much better idea (?)

old mart29/04/2020 21:18:50
3728 forum posts
233 photos

The jaws were probably ground with a very small wheel, which results in the sharp edges touching first on anything of larger diameter than the grinding wheel. Assuming the four jaw is independent, removing the edges would not be likely to spoil tis accuracy. I would put a sheet of 1000 paper on a flat surface with a square sided block on it. Then I would give each jaw in turn one light stroke longitudinally resting against the block. Try to make each stroke of each jaw as equal as possible, using a fresh part of the paper for each. Wash the jaws before re fitting them. It would be a good idea to keep each jaw in its original slot. This might be too slight to notice any improvement, but better safe than sorry.

Tony Pratt 129/04/2020 21:22:52
1934 forum posts
12 photos

By all means give the jaws a light stoning, also drinks can packing is much too thin to resist the pressure of a 4 jaw chuck use something thicker.

Tony

Brian Wood30/04/2020 09:34:22
2549 forum posts
39 photos

Bob,

I have in the past wound a couple of turns of masking tape round the workpiece to soften the bite. Like you, I have all sorts of odd ends of split copper pipe but these tend to get mangled and bent after being pushed over different sizes of job.

I agree with Clive Brown and endorse some light stoning on the jaws, especially the edges.

Regards Brian

DC31k30/04/2020 09:45:00
662 forum posts
2 photos
Posted by Clive Brown 1 on 29/04/2020 20:55:46:

...a supply of small brass packing pieces is useful but a difficulty with using these is that they fall out very readily...

See:

https://www.youtube.com/watch?v=_PuSl_PyMNI

and

https://www.homemadetools.net/forum/copper-soft-jaw-faces-lathe-chuck-66424

for how to overcome this.

Ed Duffner30/04/2020 10:41:31
834 forum posts
94 photos

How about a collet chuck? ...or turn between centers with a drive dog?

Ed.

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