is very safe, whereas, with the conditions reversed in favor of the impulse action, the intersection at
k
is more delicate. We have now seen enough to appreciate the fact that we favor one action at the expense of another.
By having a lifting angle on pallet and tooth of 8½°, a locking angle of 1½°, and a run of ½°, we will have an angular movement of the fork of 8½ + 1½ + ½ = 10½°.
Writers generally only consider the movement of the fork from drop to drop on the pallets, but we will be thoroughly practical in the matter. With a total motion of the fork of 10½° (
JAW
, [Fig. 15]), one-half, or 5¼° will be performed on each side of the line of centers. We are at liberty to choose any impulse angle which we may prefer; 3 to 1 is a good proportion for an ordinary well-made watch. By employing it, the angle
XA′Y
would be equal to 31½°. The radius
A′X