A Treatise on Staff Making and Pivoting | Page 3

rolling the blank upon the bench. If it does not come out clean, or if
soap is not used, it may be brightened by again inserting in the lathe
and bringing it in contact with a piece of fine emery paper or cloth.
[Illustration: Fig. 2.]
I draw the temper in the following manner: Place some fine brass
filings in a boiling-out cup or bluing pan and lay the blank upon these
filings, holding the pan over the flame of an alcohol lamp until the
blank assumes a dark purple color, which it will reach when the heat
gets to about 500° F. This I consider the right hardness for a balance
staff, as it is not too hard to work well under the graver nor too soft for
the pivots. At this degree of hardness steel will assume an exquisite
polish if properly treated. Another method of tempering is to place the
staff on a piece of sheet iron or copper (say 1 inch wide by 4 long),
having previously bent it into a small angle, for the reception of the
staff, as shown in Fig. 3. This piece of metal, when nicely fitted into a
file handle, will answer all the purposes of the bluing pan and presents
quite a neat appearance. Having placed the blank in the angle, lay on it

a piece of yellow wax about the size of a bean, and heat it over your
lamp until the wax takes fire and burns. Blow out the flame and allow
the staff to cool, and it will be found to be of about the right hardness.
[Illustration: Fig. 3.]
We have now arrived at an important station in staff making, a junction,
we may term it, where many lines branch off from the main road. At
this particular spot is where authorities differ. I have no hesitation in
saying that at this particular point the split chuck should be removed
from the lathe head and carefully placed in the chuck box and the
cement chuck put in its place. I believe that all of the remaining work
upon a staff should be executed while it is held in a cement chuck. On
the other hand I have seen good workmen who turned and finished all
the lower part of a staff while in a split chuck, cut it off and turned and
finished the upper part in a cement chuck. All I have got to say is that
they had more confidence in the truth of their chucks than I have in
mine. I have even read of watchmakers who made the entire staff in a
split chuck, but I must confess I am somewhat curious to examine a
staff made in that way, and must have the privilege of examining it
before I will admit that a true staff can be so made.
We will suppose that the workman has a moderately true chuck, and
that he prefers to turn and finish all the lower portions in this way. Of
course the directions for using a cement chuck on the upper part of a
staff are equally applicable to the lower. Before going further I think it
advisable to consider the requirements of a pivot, but will reserve this
for another chapter.
CHAPTER II.
The chief requirements of a pivot are that it shall be round and well
polished. Avoid the burnish file at all hazards; it will not leave the pivot
round, for the pressure is unequal at various points in the revolution. A
pivot that was not perfectly round might act fairly well in a jewel hole
that was round, but unfortunately the greater proportion of jewel holes
are not as they should be, and we must therefore take every precaution

to guard against untrue pivots. Let us examine just what the effect will
be if an imperfect pivot is fitted into an unround hole jewel, and to
demonstrate its action more clearly let us exaggerate the defects.
Suppose we pick a perfectly round jewel and insert into the opening a
three-cornered piece of steel wire, in shape somewhat resembling the
taper of a triangular file. We find that this triangular piece of steel will
turn in the jewel with the same ease that the most perfect cylindrical
pivot will. Now suppose we change the jewel for one that is out of
round and repeat the experiment. We now find that the triangular steel
soon finds the hollow spots in the jewel hole and comes to a stand-still
as it is inserted in the hole. The action of a pivot that is not true, when
in contact with a jewel whose hole is out of round, is very similar,
though in a less marked degree. If the pivot inclines toward the
elliptical and the jewel