Expert: Martin Meyer - 3/15/2009

Question
The ST 89 movements have a F/S adjustment access on the dial face. When using the key to regulate the time, the linkage transfers the key adjustment to a vertical screw that changes the effective length of the suspension rod. This vertical screw has a threaded bracket (approx 1" long and visible/accessible from the rear of the movement) with a slot, that is/can be clamped solid by a steel screw. When is this bracket to be adjusted/moved and must the screw/bracket be loosened when adjusting F/S? When is it meant to be tightened?

Answer
Hi Russ,

I know of no situation in which this screw would be tightened all the way down. It would seem that a shoulder screw would be the correct choice in this application, but I can't remember if I have ever seen an 89 with such a screw. The screw should be tightened enough that the domed washer under it holds the bracket firmly, but does not lock it. When tightened to this degree, there is no need to loosen the screw when adjusting the rating unit. The screw simply mounts the bracket while allowing it to slide up or down when the rating arbor is turned, and tightening it would be a setup issue, and not an adjustment to be made from time to time by the clock's owner.  http://www.clockmasteronline.com