[46.]Causes of Variation Between Dial Up and Dial Down.
Variations between dial up and dial down may be due to one or more of the following causes which have been arranged in two groups, the first group consisting of the most frequent and common causes, while the second group consists of causes equally detrimental but less common.
Group No. 1
1. Dirt or thick oil in one or both balance jewels.
2. Burred or marred balance pivots.
3. End of one balance pivot flat or rough and opposite pivot polished.
4. Ends of both balance pivots polished but not same form.
5. Balance pivot bent.
6. Hairspring rubbing balance arm or stud.
7. Hairspring concave or convex in form instead of perfectly level.
8. Over coil rubbing under balance cock.
9. Over coil rubbing center wheel. (Some watches).
Group No. 2
10. Balance pivots fitted too close in jewels.
11. One pivot having excessive side shake and the opposite close fitting.
12. Escape or pallet pivots bent or damaged.
13. Balance end stone pitted or badly out of flat.
14. Over coil rubbing outside coil, at point where it curves over spring.
15. Balance arm or screw touching pallet bridge.
16. Balance screw out too far, touching bridge or train wheel.
17. Safety roller rubbing dial plate or jewel setting.
18. Fork rubbing impulse roller.
19. Guard pin rubbing edge of safety roller.
20. Roller jewel long and rubs guard pin.
[47.]Short Motion Generally Indicates Where to Find Trouble.
Any of the above irregularities will cause a variation in motion between dial up and dial down and invariably the trouble will be found on the side which has the shorter motion. For instance, a pivot that is flat or rough on the end will cause a shorter motion, when it is down, than will the opposite pivot when it is down, provided that its end is slightly rounded and highly polished. The same is true when the oil is gummy or dirty in one jewel and the opposite jewel is clean and freshly oiled.
Capped escape or pallet pivots when flat or rough on one end have the same effect to a lesser degree.
It is never proper to make the end of a pivot flat or rough and thereby shorten and equalize the motion. Neither should the ends of both balance pivots be flattened at any time. On the contrary, the ends of pivots should always be slightly rounded and highly polished: there is no logical reason for having them otherwise.