Expert: Martin Meyer - 11/25/2009

Question
We have a Seth Thomas Westminster Chime (8 day ??) mantel clock that runs about 5 min slow per day. It has a German made movement (Hermle I think). I have studied your answers and pictures on-line and see the 3 prong part that should be adjusted in the direction of the + sign. How far should I have to move it to adjust for 5 min? I moved it a little with no apparent effect. Thanks in advance for your answer.
David

Answer
Hi David,

This is really a matter of trial and error; the Hermle Service Manual gives no formula for regulation. You should start with a fully wound mainspring. An insufficiently wound clock will always run slow. Start by moving the regulating unit a few notches, keep a record of how much you adjusted and how much the resulting error was. There are cases, particularly in older movements, where a movement may run slow even when adjusted to the maximum. In these cases, an additional adjustment is made by removing some of the very small disks that run around the outer surface of the balance wheel. This is a delicate operation, and should be done by a professional clock repairer.  http://www.clockmasteronline.com