As a termination to this chapter, we shall mention the use made at the present day of the recoil lever escapement in repeating watches.  We give a diagram of this construction in Fig. 170.  The lever here is intended to restrain and regulate the motion of the small striking work.  It is pivoted at V and is capable of a very rapid oscillatory motion, the arc of which may, however, be fixed by the stud or stop D, which limits the swing of the fly C.  This fly is of one piece with the lever and, together with the stud D, determines the angular motion of the lever.  If the angle be large that means the path of the fly be long, then the striking train will move slowly; but if the teeth of the escape wheel R can just pass by without causing the lever to describe a supplementary or extended arc, the striking work will run off rapidly.

CHAPTER V.

PUTTING IN A NEW CYLINDER.

Putting in a new cylinder is something most watchmakers fancy they can do, and do well; but still it is a job very few workmen can do and fulfill all the requirements a job of this kind demands under the ever-varying conditions and circumstances presented in repairs of this kind.  It is well to explain somewhat at this point:  Suppose we have five watches taken in with broken cylinders.  Out of this number probably two could be pivoted to advantage and make the watches as good as ever.  As to the pivoting of a cylinder, we will deal with this later on.  The first thing to do is to make an examination of the cylinder, not only to see if it is broken, but also to determine if pivoting is going to bring it out all right.  Let us imagine that some workman has, at some previous time, put in a new cylinder, and instead of putting in one of the proper size he has put one in too large or too small.  Now, in either case he would have to remove a portion of the escape-wheel tooth, that is, shorten the tooth:  because, if the cylinder was too large it would not go in between the teeth, and consequently the teeth would have to be cut or stoned away.  If the cylinder was too small, again the teeth would have to be cut away to allow them to enter the cylinder.  All workmen have traditions, rules some call them, that they go by in relation to the right way to dress a cylinder tooth; some insisting that the toe or point of the tooth is the only place which should be tampered with.  Other workmen insist that the heel of the tooth is the proper place.  Now, with all due consideration, we would say that in ninety-nine cases out of a hundred the proper thing to do is to let the escape-wheel teeth entirely alone.  As we can understand, after a moment’s thought, that it is impossible to have the teeth of the escape wheel too long and have the watch run at all; hence, the idea of stoning a cylinder escape-wheel tooth should not be tolerated.

ESCAPE-WHEEL TEETH vs. CYLINDER.