Metal finishing Q&As since 1989

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How to form a ball on the end of a stamping

Hi, Clive Prew here. We're reproducing an old-style carburetor from the 1930's and could do with some help with one of the parts. The choke lever was originally stamped to shape then some form of cold-forming (forging) process was used to form a ball on the end of the lever arm. I suspect the stamping incorporated some extra metal (maybe a T-shape?) on the end of the arm to provide some extra metal there to move around and form the ball. You can see the marks on the original part where the arm has been hit by the die to form the ball and change the profile leading up to it from rectangular (stamped) to tapered round.

Does anyone know who could do this kind of operation. I've had no luck.

Any advice gratefully received. I'm in England but will go anywhere to get this done.

Thanks for listening.

Clive Prew Corporate Communication
Automotive aftermarket - Ipswich, Suffolk, England
2004

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I have never owned a car that old, but I did have a lot in the late 60's. As I recall, the carburetors were often made from aluminum or zinc and I suspect they were cast. The lines you can see could be split lines from the mould. Try asking a metal caster - there used to be a few around Birmingham and Coventry, but I don't know about now. Alternatively, ask some of the vintage car restoration clubs where they get their work done.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2004