MODERN METHODS
IN
HOROLOGY.
be drawn at the outer end for a short distance. The width of the spring should be as great as it is possible to use, and allow clearance between the bottom and cap, 1-10 of a millimeter being sufficient in nearly all cases. A very quick way to test the old spring to see if it was the proper width is to break off a very short piece about 10 millimeters long and place it against the inside of the barrel. If the cap is not countersunk the spring should be as wide as the distance
Fig.
6.
from the shoulder the cap rests against to the bottom, allowing a very small amount for freedom. If the head is countersunk like Inany Swiss watches, we can use a spring as wide as the distance from the shoulder to the bottom, the recess in the cap being sufficient for the necessary clearance or free-
dom. In placing the spring in the barrel, some good main spring winder should be used, as when put in by hand they are often so badly bent that a good portion of the power is expended by the pressure against the top and bottom of the barrel, causing excessive friction, and consequently poor motion to the 164