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.
[Illustration: _Fig. 7._]
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.
[Illustration: _Fig. 8._]
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.
[Illustration: _Fig. 9._]
[Illustration: _Fig. 10._]
As previously stated, I have taken it for granted that you preferred to
finish all the lower portion of the staff while the work was held in the
chuck. I have assumed that you prefer to work in this way because I have
noted the fact that nine watchmakers out of every ten start with, and
first finish up, the lower portion of the staff. Where this method of
working originated I do not know, but it always has the appearance to me
of "placing the cart before the horse." I do not pretend to say that a
true staff cannot be made in this way, but it certainly is not the most
convenient nor advisable. We all know that the heaviest part of the staff
is from the roller seat to the end of the top pivot. Now it seems to me
that it is the most natural thing in the world for a mechanic to desire
to turn the greater bulk of his work before reversing it. Now if the
workman has been educated to turn indifferently with right or left hand,
it may make little difference, as far as the actual turning is concerned,
whether he starts to work at the upper or lower end of the staff, but
unfortunately there are few among us who are so skilled as to use the
graver with equal facility with either hand, and it is therefore an
advantage to start with the upper end, as you can thus finish a greater
portion of the work more readily. You can readily see that when you come
to reverse your staff and use the wax chuck, that by starting at the top
of staff your wax has a much larger surface of metal to cling to, and
again the shape of the balance seat is such as to secure the work firmly
in the wax, while if the reverse method is employed, the larger portion
of the balance seat is exposed and the staff is more liable to loosen
from the motion of the lathe and pressure of the graver and polishers.