Forkardt three jaw chuck renovation and bell mouth removal

FinnoUgric · Jun 22, 2020

My lathe was delivered with an old Forkardt three jaw chuck. It was shiny outside but one could immediately feel that it was nothing but inside. It had also developed a severe case of bell mouth.
I made a video on how to take this chuck apart, how to lubricate it and how to put it together.
In addition I demonstrate how one can peel off the bellmouth wit a boring bar and a tough insert (Cermet or CBN). I really hate grinding dust in my lathe.

Refurbishing Forkardt Three Jaw Chuck

ballen · Jun 25, 2020

FinnoUgric said:
I made a video on how to take this chuck apart, how to lubricate it and how to put it together. In addition I demonstrate how one can peel off the bellmouth with a boring bar and a tough insert (Cermet or CBN). I really hate grinding dust in my lathe.

I'm surprised the runout was not better after you were done with this. Some years ago I ground the inside jaws of my Logan lathe 3-jaw chuck and they are accurate over the whole range to within 0.02mm TIR.

I'm a fan of your videos. I particularly like the tear-down and reassembly of your Wohlhaupter UPA3.

hobbyman · Jun 25, 2020

I have a ten inch chuck that I got with my large Graziano 508 that I do not use. The jaws have been trued so to speak so much that the points of the jaws are almost 1/4 inch wide. Since the jaws are pretty much junk I am wondering if anyone has tried building up the pints of the jaws with bronze then machining them similarly. It would give me a chuck with soft-marring points.
I was thinking of tigging silicon bronze on while the body of the jaw is in a small pan of water to prevent softening of the rest of the jaw. Anyone tried something like that?

FinnoUgric · Jun 27, 2020

ballen said:
I'm surprised the runout was not better after you were done with this.

It is the scroll that is damaged. This means that the chuck is pretty much history in terms of accuracy.

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