Hex Soft Jaws

These are some simple soft jaws for holding thin pieces in the chuck. They were based on a design described in Model Engineers' Workshop magazine, issue 224. For the size of the chuck on the M250, I worked out I needed 50 mm AF hex bar to make these! I searched around on ebay for 50 mm AF mild steel bar but none was readily available, so I set up a saved search for 50 mm hex bar and a short bar of brass hex bar appeared. It's probably a bit ridiculous to make the jaws out of brass, but the bar was cheaper (including postage) than any suppliers I'd found of mild steel in this size (mostly because the suppliers I'd found for mild steel assumed you were buying very large quantities).

This image shows a bit more detail of how they're constructed. The surface finish is a bit poor as they've been used a few times and various witness marks are visible from that use. They are (currently) 13 mm thick; they'll gradually reduce in thickness as they are used, but I have enough brass for another set when they're too thin to be usable any more. The hole in the middle is 24 mm and there are three M3 threaded holes used to clamp the jaws in any of three orientations to the chuck. Hopefully this will further extend their usage.

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I've found them invaluable for holding thin parts in a consistent location; the photo at the top of the page shows them being used to hold a knurled adjuster screw I made for my home-made BXA tool holders. Facing the adjuster screws all to the same length was trivial with this set-up.