Polishing the Pivot Holes – Everything’s so Shiny!
Since most of the hard part was completed, I was happy to move on to polishing pivot holes, as it meant the pivots would soon be in them and turning again. Unfortunately, the pivot holes take a little while to clean, though they go much faster if the bushings are done right. To polish a pivot hole, one takes a smooth broach just like the cutting broach
except not faceted, and “burnishes” the inside of pivot holes with oil as though one were burnishing a pivot. With enough pressure and rotation of the hand, the holes will look as good as the pivots, but it gets tiring to do all ten holes (which now include the two
escape pallet pivots). Actually, it’s only hard the first time one does it, and only if the bushings are so loose that they come out during the polishing process. This is especially unfortunate because then one must go back and rebush it. I was terribly glad when none of mine fell out, and neither did any of the previously bushed holes. Having done this with oil on the smooth broach, there was now oil in the holes. To remove it, I used the xylene/mineral spirits mixture to rinse the movement and then used toothpicks to clean out any extra contamination from the holes. If contamination is present, it could react with the lubricating oils used later and cause the clock parts to become sticky and stop. Toothpick cleaning averted a disaster, however, and in no time at all, the holes were bushed and polished and the gears were free to be put back between the plates!
The Escapement – Theory, Practice, and Math
At this point, with the gears in their rightful places within the clock, it was time to calibrate the time keeping by adjusting the escape pallets. Some necessary terms are: entrance/exit pallet, entrance/exit drop, entrance/exit lock, and the lift/lock face of each pallet. The entrance pallet is the side of the pallets that allows teeth to enter between the
pallets, and the exit obviously releases them. Entrance drop is defined by the amount of distance the escape wheel rotates after being let off of the entrance pallet. It is easily visible as the distance between a tooth and the inside edge of the entrance pallet as lock occurs. Conversely, the exit drop is the distance the escape wheel rotates after
being let off of the exit pallet and is visible as the distance
between a tooth and the outside edge of the exit pallet as lock occurs. The entrance/exit lock is the amount of pallet face that “catches” the escape wheel tooth when stopping the
10