Elgin Grade 97, Cannon Pinion Adjustment

These parts are from a grade 97, key-wind, key-set Elgin pocket watch.  It's a big one, 18 size, with 7 jewels.  This one was made about 1888.

The problem was that the cannon pinion was broken.  In this photo we see the minute wheel at the left and the hour wheel at the right.  The cannon pinion is the lower part, in steel.  The hour wheel slides over the cannon pinion, and the cannon pinion fits by friction on the shaft of the center wheel.

The minute hand rides directly on the cannon pinion.  The hour hand rides on the hour wheel.  To set the watch, a watch key fits on the square end of the cannon pinion, and the hands are directly turned.  When this is done, the cannon pinion slips on the center shaft.  That's why it's just friction tight.

The cannon pinion shown here is the best replacement I could find around the shop.  These key-wind cannon pinions are relatively scarce.  The problem is that it's outer surface on this one was in rough shape, and it wasa hair too big for the hour wheel to fit smoothly.  Working on the outside of the cannon pinion is tricky.  It's walls are thin, and there's no good way to chuck the thing into the lathe.

The first step then is to make a little shaft of steel that the cannon pinion can fit tight onto.

Looking good...  Tight enough to support the part without damaging it.  The outer surface can be worked until the hour wheel fits nice and easy.

This is the hour wheel trial fit onto the cannon pinion.

This sort of work has to be done very slowly.  For one thing, it's easy to damage the cannon pinion as the outer walls are thin.  Also, if too much material is removed, you can't exactly put it back, and again the part would be ruined.

Here are the parts in place on the dial side of the movement.