A Treatise on Staff Making and Pivoting | Page 5

the level. An ascent of a liquid,
due to capillarity, also takes place, where the liquid is placed between
two separate bodies, as oil placed between two pieces of flat glass. If
the plates are parallel to one another and perpendicular to the surface of
the liquid it will ascend to the same height between the plates, as shown
at c in Fig. 6. If the plates were united at the back like a book and
spread somewhat at the front, the oil would ascend the higher as the
two sides approach one another, as shown at d, Fig. 6. If a drop is
placed somewhat away from the intersecting point, of the glasses, as
shown at m it will, if not too far away, gradually work its way to the
junction, providing the glasses are level. If, however, the glasses are
inclined to a certain extent, the drop will remain stationary, since it is
drawn in one direction by gravity and in the other by capillarity. When
a drop of oil is placed between two surfaces, both of which are convex,
or one convex and the other plain, as shown at g, it will collect at the
point n, at which the surfaces nearest approach one another. We now
see very clearly why the hole jewel is made convex on the side towards
the end-stone and concave on the side towards the pivot.
[Illustration: Fig. 6.]
Particular pains should be taken to polish those portions of the pivots
which actually enter the jewel hole and to see that all marks of the
graver be thoroughly removed, because if any grooves, no matter how
small, are left, they act as minute capillary tubes to convey the oil.
If the hole jewel be of the proper shape, the end-stone not too far from
the hole jewel and too much oil is not applied at one time, the oil will
not spread nor run down the staff, but a small portion will be retained at
the acting surface of pivot and jewel, and this supply will be gradually
fed to these parts from the reservoir between the jewel and end-stone,
by the action of capillarity.

Having examined into the requirements of the pivot and its jewel and
having gained an insight into what their forms should be, we are the
better able to perform that portion of the work in an intelligent manner.
CHAPTER III.
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