Expert: Michael Radi - 2/18/2010

Question
QUESTION: I am working on a New Haven movement.  The clock runs and strikes for a few days then the strike side stops working.  I have identified the problem as the time mainspring unwinds it eventually makes contact with the lifting lever.  When this occurs the lifting level will not drop far enough to release the warning stop pin.

I noticed that the on the strike side of the back plate there is a pin that the spring butts up against as it unwinds and keeps it away from strike side parts.  On the movement side there is a hole for such a pin (which would push the spring toward the outside of the clock and keep it away from the lifting lever).  How do you replace this pin?

Thank you,
Milan

ANSWER: The original pin was punched into the plate. It's a rivet with a long tip. To use this method to replace it, you will need to take the plates apart. That means totally disassembling the movement and putting it back together when you are done. You will also need a staking block.
You start with a piece of round stock with a larger diameter than the hole. The staking block hole should be slightly larger than the rod. Put the rod in a drill chuck or lathe, spin it and file down the diameter so that it fits firmly in the hole. Cut the rod so it goes through the plate and staking block and bottoms out on the work bench with about 1/8" sticking up through the movement plate. Tap that part of the rod with a hammer, flattening it out and filling the hole with the rod material. Finally, cut the rod to the proper length to stop the mainspring from unwinding into the works.

---------- FOLLOW-UP ----------

QUESTION: What kind of stock do I use?

Thank you

Answer
I did not specify that because I'm not totally sure. Aluminum might not hold, Brass might work but a steel that is mild enough to mill and shape with a hammer is probably what was originally used. A hardened steel might be able to be de-tempered enough by heating to red hot and the let cool down slowly.