Answer :- To fully answer your question would just about fill a book, however, you say the balance is in perfect poise; and the rates vary when watch is on edge. These variations can be caused by many other influences besides a balance that is not in poise. For instance: The hairspring must be perfectly circled to the collet, the overcoil formed so the spring develops equally in all directions and contracts equally in all directions. The regulator pins must be close and the spring perfectly flat. Sharp bends where the spring is fastened to the collet must be avoided and the hairspring pinning point in it's proper position. It should be pinned so if we drew an imaginary line thru the center of the balance when the watch is held with the pendant perpendicular, the spring is pinned on this horizontal line and to develop up over the collet. This may be either to the right or to the left. The balance pivots must be truly cylindrical and both pivots finished flat on end, being careful there is no burr on the edge of pivots. The hole jewels must be equal size and thickness, olive shaped. The corner freedom for jewel pin as it enters and passes out of the fork slot, must be equal on both sides.
The guard pin close but in no case or position should it contact the safety roller. The end shakes in your balance, pallet arbor and escape pinion must also be very close and all three of equal amount. The escapement must be set so there is a safe drop lock and some slide. Ordinarily, if your total lock and slide is equal to 1/5th the width of the pallet stone, you will have a satisfactory escapement. See that the draw, or draft, is ample by slightly lifting the lever from the banking screw and if the lever does not return to the banking screws, it will indicate there is insufficient draft and if that is the case, the guard pin will drag on the safety roller, causing a variation of time in different positions. The roller jewel must be a close fit, well proportioned, by that we mean two fifths of the diameter being cut away, leaving a flat face. A jewel so proportioned will not present a sharp edge as it enters or passes out of the fork. Examining the balance pivots with the ordinary eye loupe does not show the small defects that go to make trouble when timing a watch to positions, we recommend using a microscope, as the least irregularity on the surface of the pivot or it's contour will be detrimental to timekeeping qualities.
Examining the cap jewels carefully for any pit marks from wear and also see they are set perfectly flat. Hone cap jewel is flat and the other cap jewel out of flat, the watch will invariably show a gaining rate when running on the out of flat cap jewel.
To get best results and a most constant rate, a 1 1/4 turn of the balance or, 450 degrees, is desirable. Changing the strength of the mainspring to obtain the proper balance arc is advisable.
Generally watches are adjusted to five positions, namely dial up, dial down, pendant up, pendant right and pendant left. The greatest error between any two positions lies between the pendant up and the pendant down, due to position of pinning point. The sixth position would be pendant down and as the watch is not carried that way, that position is disregarded.
A.P. :- 1 have heard our head watchmaker telling about cutting a contrate wheel for a Swiss watch.
Tell me what make of Swiss watch has contrate wheels, or are they to be found in complicated watches only?
Answer :- A contrate wheel is one that has two sets of teeth, that is, a gear wheel that have a ring of teeth, standing at right angle to the plane of the wheel, while the other set of teeth are on the periphery of the wheel. You will find contrate wheels on all new model American watches and many Swiss models, they are cataloged as Crown wheels or main wheels.