Setting Up An Escapement
By JACOB L. HAGELOW JR.
If taken step by step escapement work will not only be found easy but also quite fascinating. First, examine the pivots on the balance staff, pallet and escape wheel. See that they are straight and well polished.
The end shakes and side shakes on same must be very close. After this has been done check the roller jewel and see that it fits the fork slot properly. It should have about .01 mm to .02 mm clearance for free action, allowing the roller jewel to enter and leave the fork slot. The roller jewel is now set upright and square and in line with the crescent as shown in Figure 1.
Now to adjust what is commonly referred to as corner freedom. This is accomplished by turning the banking screws so that the roller jewel "'ill clear the corner of the fork slot as it enters and leaves by about one degree. (On a pocket watch approximately .002 of an inch.) See Figure 2. Banking pins are placed in a watch to hold the lever in the proper position to receive the roller jewel, when the lever is up against the banking pin. They also determine the angular motion of the lever, and the angular motion of the lever determines the strength of the lock. The more corner freedom given to an escapement the heavier will be the lock ,,,,hen we set the stones. The closer the corner freedom, the lighter will be the lock.
Having taken care of the roller jewel, corner freedom and guard pin action the setting of the pallet stones is in order. These are most commonly referred to as the receiving stone and the discharge stone. The receiving stone or the one that receives the tooth first has the lesser angle, and the discharge stone the greater angle. In setting the stones place the pallet in a pallet warmer upside down. This will insure the stones being flush with the top of the pallet. Set stones in place and heat sufficiently to cause shellac to flow. In order to check the pallet stones to see that they are set properly, place pallet into the watch and give the main spring a few turns of power. By leading the lever from one side to the other with a pair of tweezers we can check the drop lock, and slide. As the escape tooth drops off one stone and on to the other, the lever should be a slight distance away from the banking pin. (See Figure 4). The distance that the lever travels after the drop to the bank determines the slide. If there is too much slide on one stone, it is easily corrected by moving the opposite stone out of the pallet and in to the escape wheel. If there is no slide or not enough slide the opposite stone must be moved back in to the pallet. The drop lock, and slide should not exceed more than 1/4 to 1/5 the width of the pallet stones.
After this work has been completed be sure to clean off any and all excess shellac that may be found on the roller jewel or pallet stones. This to be done with a nickel shellac scraper.