Drilling Chuck Jaws

D

dbassing

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Hi all,
I have an old Buck adjust-tru chuck that has bell mouthed one piece jaws. I am planning on grinding the jaws with a tool post grinder and I am trying to create a way to preload the jaws so they are in compression when I do the grinding. My idea is to machine a .250" hole in the flat of each jaw. I will insert a .250" dowel pin so that it sticks up above the surface about 1/4". I will fabricate a 1/4" thick "washer" so that I can tighten the jaws against the outside diameter, with the inside diameter large enough to give clearance for the grinding operation. I set a jaw into my mill ( Clausing 8520) and tried using a .250 carbide 2 flute center cutting end mill. Spindle speed 600. Not able to cut. So I installed a smaller diameter end mill, increased the spindle speed and still no luck. I am thinking that I should drill a pilot hole first and finish with an end mill to the correct diameter. Any thoughts on what kind of drill bit would work or any other ideas?
Thanks,
David
 
We used to bore soft jaws. We made and hardened washers in increments to mount beyond where we were boring. Are you through boring ? If not, place a thick washer, it can be soft, as far back as possible, tighten down and grind. If they are stepped jaws, make a big washer and clamp down on it with some of the larger diameter cutouts and thru grind.
 
never tried it but just watched a video of a fellow who put a bar in the chuck and tightened it up and BLUE LOCK| TITE the jaws and then ground jaw, broke the locktite and was working fine.
 
Some chucks have jaws with radial relief deeper in the chuck, in the center hole. A tube or piece of round stock can often fit in there and you can clamp on it while you grind. Please do not continue trying to drill the hard jaws. Nothing good will come of it. Consider that where the jaws are located when you grind them will likely be the only diameter where you will have minimum runout. Scrolls cannot be precision throughout their full extent, by their design, and also from use and abuse, so you might also want to think about the diameter you want to grind them at.
 
Hi all,
Thanks for all the replies and ideas and especially to Kernbigo. Such a simple solution that I don't know why I did not think of it. This is why this group is the best.
I had some aluminum that I milled to the same size and chucked them onto the lathe jaws and bored them for clearance for the grinding stone. After tightening the jaws I wired them on as a safety measure and all went very well.IMG_0630.jpg
Here is a pic showing dressing the grinding stone.IMG_0632.jpg
Thanks,
David
 
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