Choosing The Correct Clock Movement Shaft Size When Making a Clock
Clock movements are available in a wide range of sizes. There are a few important measurements you will need to have when ordering a clock movement, to ensure you get the right one to fit your application.
You’ll want to make sure that the clock movements thread length is long enough to fit through the thickness of the material you are mounting the movement to (clock dial material could be a simple clock face or decorative items like a wood plaque).
The threaded portion of the shaft (post) should come out of the mounting surface with about an 1/8” of length left for the mounting hardware. (Note: Some push on style clock movements will not have a threaded shaft.)
When using a glass front on your clock keep in mind the total shaft length (total post length). You’ll want to make sure there is enough room underneath the glass to fit the total shaft length including its minute hand cap nut or if you’re adding a second hand.
The post mounting hole of your clock dial (or mounting material) needs to have a large enough diameter to fit the shaft of the clock movement through it.
Measuring the Shaft When Replacing a Broken Quartz Clock Movement
The easiest and most accurate way to measure the shaft length on a clock movement is to use the depth gauge on a digital caliper. A ruler can also be used to measure the shaft length, if you do use a ruler to measure the shaft size make sure the ruler starts at 0, many rulers have their zero point a bit away from the end of the ruler.
Once you have found your measuring device measure from the top of the post/shaft down to the movement housing. This will give you the movements total shaft length, which will be needed when ordering a replacement clock movement.
If you are reusing your existing clock hands, you should confirm that the new movements shaft for both the hour and minute hand are the same size and shape as your existing hands mounting diameter.
For an overview of quartz clock movement parts and assembly see our article Quartz Clock Parts and Assembly Diagram.