In chapter IV I called attention to the right and wrong way of holding
the graver while using the extreme point, and also the correct manner of
applying the graver in turning conical pivots. I also called attention to
the fact that it was well to only use the point of the graver where
positively necessary, as in the back slope of the pivot, etc. In turning
the seat for the balance, as indicated at A, Fig. 15, the graver A, Fig.
1, or a similar one as shown at B, Fig. 15, should be used. The slope at
C should now be turned. In turning the pivot and seat for the roller, you
should leave them slightly larger than required, to allow for the
grinding and polishing which is to follow. No definite amount can be left
for this purpose, because the amount left for polishing depends entirely
on how smoothly your turning has been done. If it has been done
indifferently, you may have to allow considerable for grinding and
polishing before all the graver marks are removed, while, on the
contrary, if the work has been performed with care, very little will have
to be removed. Avoid the use of the pivot file by performing your work
properly to start with.
[Illustration: _Fig. 15._]
[Illustration: _Fig. 16._]
For grinding, bell-metal or soft iron slips are desirable, and the
grinding is effected by means of oil stone powder and oil. Two slips of
metal similar in shape to A and B, Fig. 16, are easily made, and will be
found very useful. A is for square pivots, etc., while B is used for
conical pivots. These slips should be dressed with a dead smooth file,
the filing to be done crosswise, to hold the oil stone powder and oil.
During the operation of grinding, the lathe should be run at a high speed
and the slips applied to the work lightly, squarely and carefully. The
polishing is effected by means of diamantine and alcohol. After the work
is brought to a smooth gray surface, slips of boxwood of the shape shown
in Fig. 16 should be substituted for the metal slips. Oil stone slips are
sometimes used in lieu of metal ones, but they soon get out of shape and
are troublesome to care for on this account. All things considered, there
is nothing better for polishing than a slip or file made of agate, say
one inch long, one-quarter inch wide and one-eighth inch thick. A slip of
this kind can be obtained from any lapidary, and after grinding with
emery and water until the surface has a very fine grain, it should be
mounted by fastening with cement into a brass socket and this is then
inserted into a small wooden handle, as shown in Fig. 17. The agate slip
should be ground to about the shape of B, Fig. 16, so that one side can
be used for square corners and the other for conical pivots. The final
polish can soon be imparted by means of a small boxwood slip, or
flattened peg-wood, and diamantine and alcohol. Never try to bring out
the final polish until you are satisfied that all graver marks have been
ground out, otherwise you will simply have to go all over the work again.
[Illustration: _Fig. 17._]
When the staff is finished from the lower pivot to the seat of the
balance, the upper part should be roughed out nearly to size and then cut
off preparatory to finishing the top part.
Attention was previously called to the fact that the majority of
watchmakers prefer to finish all the lower portion of the staff first,
notwithstanding the fact that there are numerous advantages to be gained
by proceeding to first finish up the upper portion. We have now reached
the point where the wax chuck must be used, and perhaps these advantages
may be now more clearly defined. In order that the two procedures may be
more distinctly shown, illustrations of both methods are here given.
Fig. 18 shows the popular method, the lower portion of the staff being
all completed and fastened by means of wax, in the wax chuck. Fig. 19
shows the opposite course of procedure. In both illustrations the lines
indicate the amount of wax applied to hold the work. It will be noted
that in Fig. 18 the hub of the staff is enclosed in the wax very much as
a cork is fitted into a bottle, while in Fig. 19 the hub is reversed,
just as a cork would appear were the larger portion within the bottle and
the smaller portion protruding through the neck. A study of the diagram
will readily show that in Fig. 19 the staff is held more rigidly in place
and that a greater bulk of the work is enclosed in the wax than in Fig.
18, although there is less wax used in the former than in the latter.
[Illustration: _Fig. 18._]
[Illustration: _Fig. 19._]
Before proceeding to set the staff in the wax, it is necessary to make
some measurements to determine its full length. Remove both cap jewels
and screw the balance cock in place. Examine the cock and see if it has
at any time been bent up or down or punched to raise or lower it. If so,
rectify the error by straightening it and then put it in place. Now with
a degree gauge, or calipers, proceed to take the distance between the
outer surfaces of the hole jewels and shorten the staff to the required
length. Do not remove too much, but leave the staff a little long rather
than cut it too short, as the length can be shortened later.
[Illustration: _Fig. 20._]
[Illustration: _Fig. 21._]
A very handy tool for the purpose of making these length measurements can
be constructed by adding a stop screw to the common double calipers as
shown in Fig. 20. The improvement consists in the fact that they can be
opened to remove from the work and closed again at exactly the same
place, so that an accurate measurement can be made. The all-important
point in the use of wax chucks is to get a perfect center. If you are not
careful you are liable to leave a small projection in the center as shown
at A, Fig. 21. The ordinary wax chuck cannot be unscrewed from the
spindle and restored to its proper place again with anything like a
certainty of its being exactly true, and if you insist on doing this
there is no remedy left but finding a new center each time. It will be
found more satisfactory and economical in the long run to have a
permanent chuck for a wax chuck and you will then have no necessity for
removing the brass chuck.
The center, or cone for the reception of the pivot, should be turned out
with the graver at an angle of about 60 deg. and such a graver as is shown at
B, Fig. 1, will answer admirably for this purpose. After you have
carefully centered your wax chuck, place a small alcohol lamp under the
chuck and heat it until the wax will just become fluid and yet not be hot
enough to burn the wax. Revolve the lathe slowly and insert the staff so
that the pivot rests squarely and firmly in the center. Now re-heat the
chuck carefully in order that the wax may adhere firmly to the staff,
keeping the lathe revolving meanwhile, but not so fast that the wax will
be drawn from the center, and at the same time apply the forefinger to
the end of the staff, as shown in Figs. 18 and 19, and gently press it
squarely into place in the wax chuck. The lines in Figs. 18 and 19
designate about the right amount of wax after the work is ready, but it
is well to add a little more than is shown in those figures, and you
should be careful to keep the wax of equal bulk all around, or when it
cools it will have a tendency to draw the staff to one side. Now remove
the lamp and keep the lathe revolving until the wax is quite cool, when
it should be removed, by means of a graver, down to the dimensions
designated by the lines in Figs. 18 and 19. When this is accomplished
re-heat a little, but only enough to make it soft, but not liquid, and
placing a sharpened peg-wood on the tool rest proceed to the final truing
up, by resting the pointed end against the hub.