Our wire has been roughed out into the form of a staff, has been hardened and the temper drawn down to the requisite hardness and we are now ready to proceed with our work. As I said before, we have now arrived at a point where many authorities differ, i. e., as to whether the finishing of the staff proper, should be performed while the work is held in the chuck, or whether a wax chuck be substituted. We will take it for granted that you have a true chuck and that you prefer to finish all the lower portion of the staff while held in the chuck.
Before we proceed with our work it will be necessary for us to make some accurate measurements, as we cannot afford to do any guess work by measuring by means of the old staff. I have used a number of different kinds of calipers and measuring instruments for determining the various measurements for a balance staff, but have met with more success with a very simple little tool which I made myself from drawings and description published some years ago in The American Jeweler. This simple little tool is shown in [Fig. 7], and has been of great service to me. It consists of a brass sleeve A, with a projection at one end as shown at B. This sleeve is threaded, and into it is fitted the screw part C, which terminates in a pivot D, which is small enough to enter the smallest jewel. The sleeve I made from a solid piece of brass, turning it down in my lathe and finishing the projection by means of a file. The hole was then drilled and threaded with a standard thread. The screw part C, I made of steel and polished carefully.
Fig. 7.
Fig. 8.
To ascertain the proper height for the roller, place it upon the tool, allowing it to rest upon the leg B, and set the pivot D in the foot jewel. Now adjust, by means of the screw C until the roller is in its proper position in relation to the lever fork. This may be understood better by consulting [Fig. 8], where A is the gauge, C is the roller, E is the lever, F is the plate and G is the potance.
Now in order to locate the proper place to cut the seat for the roller, remove it from the foot of the gauge and apply the gauge to the work as shown in [Fig. 9]. The foot of the gauge resting against the end of the pivot, the taper end of the gauge will locate accurately the position of the roller seat. In order to locate the proper position for the seat for the balance, proceed the same as for the roller, except that the foot of the gauge is lowered until it is brought sufficiently below the plate to allow of the proper clearance as indicated by the dotted lines at H. Now apply the gauge to the new staff, as shown in [Fig. 10], and the taper end will locate the exact position for the balance seat.
Fig. 9.