Numbers on chuck jaws

If you change out the jaws on the chuck, you want them to go back in the same order and position. The numbering process makes that easy.

But on my Vicmarcs if I remember correctly they won't go together but one way. Since I bought two of them to keep the jaws I use the most in seperate chucks, I haven't taken them apart for some time. But when I did I seem to remember that the jaws were grooved to be oriented as an integral part of the scrolling movement. With that in mind, it would allow you to put the jaws back in the order they must be in for the chuck to operate properly.

I know for sure that is true on a small Taiwanese chuck I have. It won't go together any other way than the way it is numbered and it is because the jaws on it (had it apart a few months ago) are definitely grooved to be part of the scrolling gear mechanism.

Robert

Because the jaws are not identical, and the correct jaw should be in the correct slot for the chuck to work correctly. In specific, the teeth on the back of each jaw are in different locations. Putting the jaws in the wrong slots will cause the chuck to not close on-center.

Chuck jaws are turned as a single piece on a metal lathe, drilled for the screw holes, and *then* cut up. They're marked before they're cut up so that when you "reassemble" them, they're in the same relative positions as when they were made, so that when the jaws close up they fit perfectly.

Otherwise, any error in the cutting is magnified by any misplacement in the jaws, and you end up with imperfect fits.

In theory, you could place the jaws in any position on the chuck, as long as the *relative* position of the jaws remains correct. I.e. move all jaws one spot clockwise and they should still fit. The numbers on the body remind you of which relative positioning is the right one (clockwise vs counterclockwise, usually).

As the others have said, it helps to get good alignment when putting the jaws back in place because they are cut from one piece of steel. You can get an idea of this from the section on my site about making bottoming or "Cole" jaws in wood.

My machine chuck is like that, I didn't think about that option for the Pinnacle chuck. My Supernova is stamped, but the mounting shoes give you the same mount for each jaw. The mounting shoes are all different underneath, though, because of the spiral.

On my machine chuck, the jaws are reversible - but you have two swap #1 and #3 when you reverse them, because of the spiral.

The Pinnacle chuck appears to be the shoe-type, like the Supernova and Oneway chucks, though.

Which is true in my experience with Novas. Having been sent two sets of mismatched, according to the numbers, jaws by KMS, I filed them into a fit rather than go through the complicated return and replace procedure I finally got through multiple inquiries.

Put me ahead of the game, actually. The first sets I got with the chucks were numbered on the face where they could be obscured by crud, the second on the bottom, the third round purchase has dots placed by a punch rather than numbers. Same as the ones I had to fix.

I have to ask this question- Jaws are numbered at the factory when they are cut apart right? Does this mean when I buy another set they will not fit properly?

They're numbered so they fit *each other* within a set. I.e. the four jaws you get in a set originally came from the same physical block of metal, the numbers tell you where they were in the block before they were cut apart. That's all the numbers are for, not for compatibility with other jaw sets or chuck bodies.

Now, if for some reason you bought two of the same size jaw, you'd have to be careful to keep the sets together as sets. You can't swap a #3 jaw from one 50mm set with a #3 jaw from a different 50mm set.