Micromechanics and Watchmaking: Bushings

This week we started by working on bushing a worn barrel bridge. I had some practice last week turning and installing a bushing in the center wheels lower hole as its jewel had cracked. After some trial and error I found a very effective way to turn bushings and centering holes accurately.

The first step here was to center the bridge in the face plate. Once this was accomplished I was able to take a high speed steel graver and open up the hole to a larger and even diameter which would then be centered properly.

Next I found a bronze bushing of roughly the correct dimensions and fitted it onto the lathe using a 1dg taper on a brass rod. Once it is secured on the taper, I used the slide rest and carbide cutter to bring the diameter to the correct dimension followed by facing the part off until it was the correct thickness.

Once this was finished the only step before installing it in the plate was to get the bushing's hole around the proper dimension. I did this using a cutting broach while the bushing was held in my pin vise.

Finally the bushing is pressed into the plate and a smoothing broach is used to bring the bushing's hole to the final dimension while also nicely polishing the inside of the hole.

All in all it was a fun task to complete, and I'm getting very good at turning out bushings quickly. It will be a nice skill to have as backup if I ever need to do any refurbishment work in the future.