new life for old chuck

[old martParticipant @oldmart]

When we were given the Atlas 12 x 24 lathe, it had with it a very poor 5″ Pratt chuck and I discarded it after removing the backplate. Forgotten for years, I happened to find where it had been dumped and thought about the possibilities of getting it working again. The original hard jaws had been cut down and steel tops welded on and my first thought was to replace them with a set of better ones. We have loads of 5″ Pratt Burnerd jaws, but unfortunately although the teeth pitch matched the rest didn’t. I have photographed some of the proceedings, but didn’ think of taking pictures of the jaws before they were milled. There was enough left to make them simple tenon with 6mm screw holes. I used a 40mm shell mill with 4 APMT11 inserts and the welded and case hardened jaws used up both ends of a set of inserts taking the tops down to a starting height. The tenon slots were done with a 6mm solid carbide Totem endmill and they have ended up about 3.3mm deep and 10mm wide. The 5mm holes for tapping were drilled with a solid carbide stubb drill about 14mm deep. Tapping was definitely tougher than mild steel, but full threads are about 11mm deep now. The tops have yet to be made, I will use aluminium. I also shortened the inner ends of the jaws by about 6mm Which also meant loosing the end scroll teeth, but there are still 6 left and they do feed into the chuck correctly.

 

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