Making a Pallet Arbor

An 18 size Waltham Tracy Appleton model had a broken pivot on the pallet arbor. The usual repair, other than replacing the part if possible, would be to re-pivot the arbor. This involves drilling a hole into the end and fitting a freshly made steel pivot in. I have never had much luck with that in hard steel, so in this case the thing to do was to make a whole new arbor.

After taking detailed dimensions of the original, we start with a rough outline cut out of a rod of hardened steel on the lathe, with a carbide graver.

When we get closer, and both pivot ends are roughly in place, the part is cut off the rod.  Note that there is to be a slight taper to the arbor.  It starts to show here.

Here's a tip...  If you take a razor blade and place its edge against a fine file, and strike it with a hammer.  It turns into a very fine saw.

The key is a very, very sharp graver, and to work very slowly.

Getting closer to the final dimensions we switch to an arkansas stone, and then to a jasper stone.

The final pivots are .2 mm in diameter (two tenths). This has to be exactly right. Too big and the part will bind in the jewels, too small and the extra side shake will disrupt the escapement.

The pivot are finally burnished with a steel burnisher, and polished to a mirror finish.

Here is the completed assembly. The pallet is friction fit (in the staking tool) so thus the slightly tapered shape of the arbor is critical. It can not be adjusted.

The pallet must fit with the right amount of snugness at exactly the right height so that the fork addresses the roller correctly on the balance end, and at the other end the escape wheel teeth come midway on the faces of the pallet jewels.

Finally, the new part in place, a well running watch.