Chuck Jaw Terminology Question

[Wreck™Wreck]

I see what you mean, but if the radius of curvature of the workpiece exceeds that of the bite only those inner two corners will make contact. Think about gripping hex stock with those jaws.

Holding hex stock in a 3 jaw chuck is one of the easiest things that you will ever do, the chances of spinning that are roughly zero (-:

 

[Bill C.]

The grind marks remind me of a vertical grinder like a very small Blanchard. You could chuck up a perfectly round shaft that would fit inside the spindle area and regrind the jaws. I recall awhile back that approach was mentioned. I never did it. I had more trouble getting a few old chucks to run concentric.

Good luck with your chuck.

 

[Bill C.]

quality,price, expectations

I was surprised, a few years ago, that some manufacture's standards allow their new chucks would have run out.

 

[Wreck™Wreck]

I was surprised, a few years ago, that some manufacture's standards allow their new chucks would have run out.

ALL manufacturers scroll chucks have run out, every one.

 

[John Hasler]

Holding hex stock in a 3 jaw chuck is one of the easiest things that you will ever do, the chances of spinning that are roughly zero (-:

Of course it won't spin, but with the jaws ground like that it will be gripped only those long points on the inner ridge nearest the face of the chuck. The outer part of the jaw will make no contact at all.

 

[David VanNorman]

The scroll teeth on the back of the jaw will tell you which way they are to go. I do have a chuck that the jaws will go either way.

 

[markba633csi]

The issue for me is that the two teeth on each step are not in the same plane. Not equidistant from the spindle axis. Whoever performed the final grinding took off too much material off the outer teeth compared to the inner ones. The outer tooth on each jaw doesn't touch the workpiece at all, which will lead to a serious lack of gripping force.
The Shars branded picture is what I was expecting, but I'm getting the impression from Shars that they may have made hundreds of defective jaw sets like this and won't be able to supply anything better. I'll keep you all posted tho.
I may end up buying the 340$ Pratt-Burnerd from the UK after all..

 

[Tony Wells]

I agree with Ken. If you look closely at virtually all the non-contact "edge break" grinds, none of them are particularly consistent. This would give the appearance than the cylindrical portion of the grind was messed up, but I don't believe it is. Can you try a small precision square, or Jo block in the corner? Something to see if it really is misground. That side chamfer in particular, and I suspect all of the non-critical ones were done freehand.

 

[John Hasler]

The issue for me is that the two teeth on each step are not in the same plane. Not equidistant from the spindle axis.

I think that they probably are equidistant from the spin axis: they are ground cylindrically. That only matters if the work is round and of a diameter equal to or less that that of the cylinder the tooth was ground on, though.

 

[RJSakowski]

Looking at the photos, the jaws can be made right with some careful grinding. While you shouldn't have to do repair work on a new chuck, it will make it usable.

It is disconcerting at how many items purchased in recent years have to be reworked before use. And its not just Chinese products. I have had similar experiences with Made in USA products.

Bob