The Play of Pivots
Saunier gives the following rules for the play of escapement pivots: In the cylinder escapement, about one-sixth the diameter of the pivot; in the duplex escapement, about one-tenth the diameter of the pivot; in the lever escapement, about one-eighth the diameter of the pivot. A large hole causes the pitching of the depths to vary with position, and a deficient play renders the escapement more sensitive to thickening of the oil. There is less inconvenience when the play is somewhat in excess than when it is deficient. In determining the play of train wheel pivots, proceed as follows: Allow the train to run down, and if it does so noisily, or by jerks, it may be assumed that some of the depths are bad, in consequence either of the teeth being badly formed, or the holes too large, etc. To test the latter point, cause the wheels to revolve alternately in opposite directions by applying a finger to the barrel or center wheel teeth, at the same time noting the movement of each pivot in turn, in its hole. A little practice will soon enable the workman to judge whether the play is correct. The running down of the train will also indicate whether any pivots are bent. It is important that the center pivots project beyond the holes in the plate and bridge.