Is my Atlas 3-jaw chuck bad?

U

UtTex

H-M Supporter - Silver Member
H-M Supporter - Silver Member
Joined
Feb 19, 2024
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I've only just begun using my Atlas Craftsman 12" (101.07383). Since I'm a total newbie, I'm not sure if my suspicions are correct. It seems to me that the Atlas 3-jaw chuck (AB-435) should grip the workpiece equally along the entire axial length of each jaw. However, when chucking in a piece of round stock, I noticed some daylight between the part and the end of the jaws. I double-checked to make sure it wasn't a problem with the stock being tapered by chucking an endmill; it looked the same. I used a feeler gauge to measure the gap at approximately .007", .005", & .004" on the three jaws and could get the .0015" gauge to slide in almost even to the chuck face on the worst one. I haven't taken the jaws out to check for flatness yet, but the gap appears to be a uniform angle away from the centerline of the bore.

So, is this normal? Is it a common aberration? Can it be repaired? Thanks.
 
Pretty common for smaller, less expensive chucks that have been used by people who think that tighter is better. The crossbars on the chuck wrenches used to tighten these chucks often are bent from using a cheater pipe.

It is possible, and accepted practice, to regrind the clamping surfaces to make them straight again. Here is a Youtube video of how one guy resurfaced his jaws. He was trying to reduce runout, but the same process will correct your "flared" jaws.

 
Thanks, Provincial. I will give the boring bar a try once I'm a bit more practiced on the lathe. I have a 4-jaw and another (larger) 3-jaw I can use until then.
 
The chuck is worn. Even if you grind the jaws, it won't restore the chuck to like-new condition
For hobby use it may be ok though
 
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