Soft jaws

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

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**

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

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

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

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.

DC31k:

Thank you for your detailed comments and the links.