Hi Folks,

I am truing the chuck jaws on the original 5" OD (Logan #431) 3-jaw chuck for my 10" Logan lathe (SN 6774A). I would like to grind the outsides of the *inside-mount* jaws. To do this, I need to pre-load them against the scroll at some particular position of the jaws, either with a ring, a hose clamp, or... read what I did for the insides of the jaws in my next post.

But what radius should the chucks be ground to? The jaws are so rounded and worn that I can't even easily tell what the radius of curvature is by looking at it, but it's something large, about the OD of the chuck body itself. Is that what it generally is when new? Is there some magic number one typically grinds to? With a large radius in the jaw, it seems I will have 6 points of contact against any part that has a smaller radius. Is this what one wants with the inside-jaws?

Does anyone (Scott Logan?) know to what dimensions the original Logan jaws were ground?

Thanks in advance for the replies.

Dan