Fig. 12.
Each division on the gauge represents 1/2500 of an inch, which is all that we require. The diameter that the pivot should be, can be ascertained by inserting a round pivot broach into the jewel and taking the measurement with the pivot gauge, and then making the necessary deduction for side shake. Slip the jewel on the broach as far as it will go, as shown in [Fig. 12], and then with the pivot gauge, take the size of the broach, as close up to the jewel as you can measure, and the taper of the broach will be about right for the side shake of the pivot. If, however, you prefer to make the measurement still more accurate, you can do so by dipping the broach into rouge before slipping on the jewel and then remove the jewel and the place which is occupied on the broach can be plainly discerned and the exact measurement taken and an allowance of 1/2500 of an inch made for the side shake. Another method, and one which is particularly applicable to Swiss watches, where the jewel is burnished into the cock or plate, is to first slip on to the broach a small flat piece of cork and as the broach enters the jewel the cork is forced farther on to the broach, and when the jewel is removed it marks the place on the broach which its inner side occupied, and the measurement can then be taken with the gauge. If care is used in the selection of a broach, that it be as nearly perfect in round and taper as possible, by a little experiment you can soon ascertain just what part of the length of the broach corresponds to one degree on the gauge and by a repetition of the experiment the broach can then be divided accurately, by very minute rings turned with a fine-pointed graver, into sections, each representing one degree, or 1/2500 of an inch, and the measurement will thus be simplified greatly.
Fig. 13.
As before stated, much depends upon the condition of your gravers and the manner of using them. It is of the utmost importance that they be kept sharp, and as soon as they begin to show the slightest sign of losing their keenness, you should sharpen them. The proper shape for balance pivots was shown in [Fig. 4]. Now let us examine into the best positions for holding the gravers. In [Fig. 13] two ways of holding the graver are shown, A representing the right and B representing the wrong way. If the graver is applied to the work as shown at A, it will cut a clean shaving, while if applied as shown at B it will simply scrape the side of the pivot and ruin the point of the graver without materially forwarding the work. Again, the holding of the graver as indicated at A has its advantages, because the force of the cut is towards the hand holding it, and should it catch from any cause the jar of the obstruction will be conveyed immediately to the hand, and it will naturally give and no harm will be done. If, on the other hand, the graver should meet with an obstruction while held in the position indicated at B, the force of the cut will be in the direction of the arrow, downward and toward the rest, and the rest being unlike the hand, or rather being rigid, it cannot give, and the result is that the work, or graver, or both, are ruined. In [Fig. 14] two other methods of holding the graver are shown. The general roughing out of a staff should be done with the graver held about as shown at A, [Fig. 13]; but in finishing, the graver should be held so that the cut is made diagonally, as indicated at A, [Fig. 14]. It is rather dificult to explain in print just how the graver should be held, but a little experiment will suffice to teach the proper position. The best indication that a graver is doing its work properly, is the fact that the chips come away in long spiral coils. Aim to see how light a cut you can make rather than how heavy. Never use force in removing the material, but depend entirely upon the keenness of the cutting edges. Never use the point of the graver, except where you are compelled to, but rather use the right or left hand cutting edges. By following out this rule you will find that your work, when left by the graver, requires little or no finishing up, except at the pivots.
Fig. 14.
At B, [Fig. 14], is shown the correct manner of applying the graver when turning a pivot. Hold the graver nearly on a line with the axis of the lathe and catching a chip at the extreme end of the pivot with the back edge of the graver, push slightly forward and at the same time roll the graver towards you and it will give the pivot the desired conical form. By keeping the graver on a line with the length of the pivot, all the force applied is simply exerted in the direction of the chuck, and does not tend to spring the pivot, as it would were the extreme point applied, as in [Fig. 13]. When we come to such places as the shoulder of the back slope, the seat for the roller, balance, etc., we must necessarily use the point of the graver.