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Soft jaws

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Steve Neighbour03/08/2022 10:19:20
120 forum posts
1 photos

If any of you watch 'Blondie Hacks' on YT - she made some copper soft jaw 'covers' which work really well.

They are quick and easy to make - I used a piece of copper sheet, and cut a template to suit, folded to shape so that they simply 'clip' onto ea jaw.

https://youtu.be/9YSRT1MZ3jY

obviously nowhere as good as a set of purpose 'machined' ones - horses for courses !!

Steve

Paul Lousick03/08/2022 11:59:32
2078 forum posts
728 photos

Protective jaw covers are OK to prevent marking the part if run-out is not critical in a 3-jaw chuck. For an accurate mounting if the jaws are worn or not an adjustable chuck are machinable soft jaws.

Youtube video showing how to bore the soft jaws to suit your job using a jaw spider **LINK**

DC31k03/08/2022 17:34:56
727 forum posts
2 photos
Posted by ega on 03/08/2022 09:45:31:

The precise construction is not clear, to me at least, from the Myford leaflet

The photo below the Myford leaflet explains it very well. The groove in the hexagon locates in the tongue on the base jaw. The flat of the hexagon (which is perpendicular to the groove) locates on the step in the jaw, the back side of the cross-groove milled in the jaw.

It relies on the pressure from the work pushing the soft jaw against the step, so only five out of six degrees of restraint are provided, so you could not grip the inside of a tube with the jaws, but for normal, external gripping, it should be highly repeatable.

The concept is 50% of a traditonal tenon-and-groove two-piece jaw setup. See for example,

https://www.chestermachinetools.com/product/3-jaw-self-centering-2-piece-jaw-chucks-plainback/

https://rdbarrett.co.uk/product/soft-top-jaws-for-bison-2-piece-jaw-chucks-american-cross-tenant-by-bison/

For information, this type of jaw is made to ASA B5.8 or IS 15248 2002 or ISO 3442 (and the dimensions in the international versions are direct metric conversions of the original imperial units).

Have a look at 11:47 onwards here: https://www.youtube.com/watch?v=JplJAxX3buA

steamdave05/08/2022 20:02:37
521 forum posts
45 photos

Just to show that I do follow up on the answers to my questions. Well, some of them!

soft jaws.jpg

These are my soft jaws. 2-1/4" Ali hex. The holes are .700" and the jaws are locked in place by M3 cap screws with the heads reduced in diameter a few thou. The front faces have deliberately not been faced.

Dave
The Emerald Isle

old mart07/08/2022 15:06:49
3912 forum posts
268 photos

That is a good design to use with standard jaws, Dave. I suggest you drill and tap at least 2 more locking holes, up to 6 if you want, so the jaws can be rotated when the first position gets used up.

ega07/08/2022 15:30:50
2567 forum posts
203 photos

DC31k:

Thank you for your detailed comments and the links.

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