The most difficult part of replacing a clock movement for most people, is just measuring the length of the hand shaft. These two measurements are the most important measurements you have to take. You check the overall length of the hand shaft (A) and the length of the threaded part (B), where the hex nut goes. It’s really not difficult to do. Clock movements are normally attached to a clock dial or other surface from the back side. The thickness of whatever the movement is mounted to will determine the shaft length needed. To check this, you must have the clock movement removed from the clock case. Remove the clock hands and check for a small brass nut that would be under the hour hand and holds the movement in place. Turn it counter clock wise and this should release the clock movement from the clock case. A pair of needle nose pliers usually works well here. Occasionally, you may see a clock movement that is secured from the back with screws, and does not have a brass nut on the clock dial. If this is the case, then removing the screws on the back of the movement should release it from the case. For example, if your clock has a thin metal dial (1/16” ?) that is mounted to a ¼” plywood base, then the thickness the hand shaft has to go through is ¼” + 1/16” = 5/16”. It’s usually a good idea the make sure that the threaded part of the shaft is 1/8” longer than the thickness is. This extra 1/8” is used to secure the movement in place with a brass washer and hex nut. […]
