Grinding the small 4" 618/101. Chuck Jaws

LX Kid

LX Kid

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Finally got around to checking the run out on my Craftsman 101 small 4" 3-jaw chuck. My chuck run out was .006" and knew I had to grind the jaws. The thru hole is so small I had to come up with a way to pull the jaws tight enough to be able to get my pencil grinder in the hole. I used safety wire pulling the jaw as tight as possible so there was no play. After grinding my jaws the run out is now less than .001". I am cutting some large 3/4"X 9" door hinge pins and there is .003"to .005" difference between chuck and live center. There is no noticeable play in my live center and doing a left hand cut. I've gotta find a cross slide follower for the long things on my little lathe.
 

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The way you did the grinding is not the proper way, it may have worked this time, but the jaws need to be restrained in the other direction; there have been many posts on the subject on this forum regarding procedure; I did it with a small chuck years ago by using a carbide drill to drill a small hole in the face of the chuck jaw, inserting pins and clamping down on a narrow tubing ring.
 
benmychree said:
The way you did the grinding is not the proper way, it may have worked this time, but the jaws need to be restrained in the other direction; there have been many posts on the subject on this forum regarding procedure; I did it with a small chuck years ago by using a carbide drill to drill a small hole in the face of the chuck jaw, inserting pins and clamping down on a narrow tubing ring.
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Yes your absolutely correct. There was no way that I could find something to insert inside the jaws, and then tighten down, and still be able to get my grinder pencil inside. Yes I did take a chance but luck was with me! It's a new chuck and I never even thought about doing as you suggested with the pins. Thanks
 
benmychree said:
The way you did the grinding is not the proper way, it may have worked this time, but the jaws need to be restrained in the other direction; there have been many posts on the subject on this forum regarding procedure; I did it with a small chuck years ago by using a carbide drill to drill a small hole in the face of the chuck jaw, inserting pins and clamping down on a narrow tubing ring.
Click to expand...
I did the same with the small holes and pins.
I would recommend going another direction. the holes require absolutely precise drilling.
I have seen others create 3 pieces that lay flat on the chuck and as the jaws close it pulls them in, and locks the jaws. The pieces need to be the exact same size... not a problem glue them together with hot glue, machine them, file or grind them to size, the heat to separate, and use them.

Look around, as John said it's been documented over and over here.
 
Other folks have made a plate with a center hole and 3 other holes that the jaws fit through to allow grinding, a search of the subject should show how to go about it. Strange that a new chuck would run out so much; chucks with wear to the scroll would not respond to the method you used. as the inside/outside chucking would be different.
 
woodchucker said:
I did the same with the small holes and pins.
I would recommend going another direction. the holes require absolutely precise drilling.
I have seen others create 3 pieces that lay flat on the chuck and as the jaws close it pulls them in, and locks the jaws. The pieces need to be the exact same size... not a problem glue them together with hot glue, machine them, file or grind them to size, the heat to separate, and use them.

Look around, as John said it's been documented over and over here.
Click to expand...
Precise drilling is not necessary as the ring chucked on equalizes the force and all jaws have equal tension on them.
 
"Not so lucky after all!" Checked my runout and back to square one. My runout is now .006" coming out of the chunk and .004" coming out of the spindle nose! Maybe my 74 year old lathe just don't want to cooperate anymore like it was still a kid. LoL Maybe I check runout again after letting it run about 30 minutes and see if cold and heat have an effect.
 
I wonder if your lathe's wear situation makes the finish grind tapered, that may account for the problem.
 
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