PRACTICAL RECIPES.
=495.= The practical operations of the watchmaker are numerous and of
a very varied character. Detailed instructions in regard to the proper
conduct of a large number of them will be given in this part of the
work, and frequent references will be made to former parts of this
volume, whenever by so doing repetition can be avoided.
The operations herein discussed are often of so dissimilar a nature
that it has been found impossible to classify them in such a manner
that will always ensure the reader finding the information he requires
without waste of time; and any risk of this would seriously impair
the value of such a hand-book as the present. A very full index has
therefore been added, and when seeking for details concerning any
particular operation, this should in all cases be first consulted.
THE PLATE.
=496.= =To Make a Plate.= The sheet of brass having been prepared in
the manner explained in article =103=, roughly rounded and smoothed on
one face, is cemented to the chuck of a lathe. Turn out the other face
of the plate very flat, and make the circumference square.
When using a lathe the face must first be roughed out, and then the
plate is to be cemented to a perforated plate, so that it can be
centered and finished. Smooth the exposed face with a well-set cutter
and turn the inside and outside of the edge; then make sure that the
whole is concentric by a light cut with a cylindrical drill in the
center hole. After removing and cleaning the plate it is set up in the
dogs, and the face that has hitherto been untouched is gently dressed
with the graver.
There will thus be left a narrow ring at the edge that is not touched
by the graver: this may be levelled with a smooth-cut file, and the
whole surface then smoothed as explained in article =171=.
[Illustration: _Fig. 229._]
If a lathe is not available, the plate must be cemented to an arbor of
the form shown at Y, Fig. 229. The heel of this is received in a runner
of the turns, while the point of the opposite runner is received by the
hole in the center of the plate, which is thereby held in close contact
with the plate of Y, the revolution being, of course, produced by a
bow. While the cement is still hot, a stick resting on the T-rest will
serve to ensure the concentricity of the plate until it is set. This
setting may be rendered more rapid by the application of cold water.
Turn out the plate with a hooked graver made of a worn out file,
and, if the upper or under side does not run true, turn the portion
that projects beyond the chuck with a graver, and, when the plate is
removed, face the surface, taking the flat ring produced by the graver
as a guide, and taking care to avoid altering any portion of it.
The smaller sinks can also be made in the same primitive manner, to
which we have only drawn attention for the sake of watchmakers who are
ill-provided with tools. But we would at the same time point out that,
at the present day, there should not be a single one who does not know
how to extemporize a lathe-head.
=497.= =Cocks and Bars.= If it is required to make all the cocks and
bars of a watch, prepare a _false plate_, the thickness of which is a
trifle greater than that of the highest cock or bar; then turn on the
under side a series of sinks to correspond with the thin portions of
the cocks and bars. Cut the several parts out of this plate with a fine
saw, and it only remains to shape their contours with a file.
The same method may be adopted if a number of identical cocks have to
be made at a time.
THE BARREL.
INCLUDING ARBOR, STOPWORK, MAINSPRING, ETC.
=498.= =To Make a Barrel.= Having trued both faces of the brass, and
drilled a central hole rather less than that finally required and
exactly perpendicular to the faces, turn away the brass from the inside
(leaving a considerable excess of metal at the center to form the
shoulder), and form the ring on which the teeth are to be cut, if it
is a going-barrel, in the ordinary lathe on a wax chuck. Then fasten
the plane surface, which must be quite true, to a smooth plate that
is of uniform thickness and has a hole in the center to permit the
passage of the pump-center. Having fixed the plate by the mandrel dogs,
finish with well-set gravers: 1 the inside; 2 the external cylindrical
surface both of the barrel and of the ring left for the teeth; 3
the barrel-cover groove; and 4 with a fine-pointed cutter slightly
enlarge the central hole. By this means it is possible to ensure that
the barrel will turn true and in the flat. Smooth the inside, more
especially the groove, the corner of which must always be carefully
smoothed and polished.
The cutting of the recess in the barrel-cover (of a Swiss or French
watch) that gives freedom to the motion work, as well as the recesses
for the stopwork, will not present any difficulty when the workman is
provided with a lathe with or without a slide-rest.
[Illustration: _Fig. 230._]
When there is no slide-rest, the tool shown at D, Fig. 230, can be used
for making the groove. A strip of metal of rectangular section has a
small cutter clamped in a slot in its surface at a slight inclination.
By releasing the two screws of the clamp, this cutter can be advanced
to any required extent, and in the strip of metal are two or three
slots having different degrees of inclination, so that the one can be
selected that corresponds with the depth of the groove.
=499.= =To Make the Star-Wheel Sink.= This is easy on the lathe, the
requisite degree of eccentricity being given to the barrel-cover by
means of the pump-center.
=500.= =The Cover: Form of the Groove.= As in making the barrel, a
thick ring must be left at the middle of the cover to be afterwards
removed.
[Illustration: _Fig. 231._]
Fig. 231 is an enlarged figure to show the mode in which a cover
is held in its groove. The two are so formed that the cover shall
pass into the recess with the least possible resistance, and yet be
held firmly without a risk of rotation. It is, nevertheless, a good
precaution to fix a pin in the rim so that it shall prevent such an
accident.
=501.= =Barrel Hook.= It is necessary to observe that a certain amount
of caution must be exercised in regard to the barrel hook, for at
least three-quarters of those met with are badly made. A large hook,
projecting far into the barrel, as often occurs, occupies a needless
amount of space, and at times occasions the breaking of the spring.
One that is badly formed or does not project sufficiently allows the
spring to escape. A hook should project rather beyond the thickness of
the spring; if too thick the spring will be weakened at its eye; if too
thin, it is liable to give when the pull of the mainspring is exerted
on it.
The circumference of the barrel must be drilled through exactly midway
between the bottom and the groove, in a direction that is slightly
inclined, so as to resist the pull of the mainspring. A thread is cut
in this hole with a conical tap, arresting its advance just before
the full threads are reached, in order to make sure that the brass
screw to be subsequently inserted shall hold firmly. Then tap the
brass wire from which a hook is to be made. Allowing a length to
project beyond the screw-plate equal to about one and a half times the
thickness of the mainspring, file the two sides flat, round off the
point, inclining it slightly backwards, and form the hook with a fine
screw-head slitting or other suitable file; then remove the wire from
the screw-plate and hold it in a pin vise.
[Illustration: _Fig. 232._]
The angle _a_ (C′, Fig. 232) is now filed down so as not to project
within the barrel; any burr that might interfere with its introduction
is also removed and the hook is then screwed into its place. It will
be easy to ascertain whether the various heights, etc., are correct
before screwing it tight home. Then screw the hook into position so
that it requires the application of some force in doing so and cut off
the external portion level with the surface of the barrel, employing a
sharp cutting file. But if it appears necessary to withdraw the hook
to make any alteration, this should be done before bringing it to the
final position.
Some watchmakers do not take such precautions; they fit a piece of hard
brass wire to the hole, beveling off the end that is to form the hook,
then cut off the wire nearly flush with the outer surface of the drum
and, resting the back of the hook against a piece of steel, give a blow
with the hammer so as to bend the point of the hook. But this method,
although expeditious, is not the best and it does not always succeed.
=502.= =To Repair a Barrel.= When the play or the end shake of the
pivots is considerable, bush the holes with bushings turned on a smooth
taper arbor. They must not be riveted roughly, as there is a danger
of distorting the bushing or of causing the bottom of the barrel to
“cockle.”
If there is any fear that the bushing will be thus distorted or that
the barrel will not run true after the operation, it will be well to
employ large bushings in which the hole is less than that ultimately
required. Then center from the circumference and enlarge the hole, at
the same time truing it.
Some practical watchmakers, if the bottom of the barrel is thin, or if
special solidity is requisite, fear that the bushing may become loose;
they, therefore, enlarge the barrel-hole and make it square; then bush
it with a piece of plain brass, and having centered the barrel by its
circumference in the lathe, drill a central hole.
It is hardly necessary to observe that, when the holes in both barrel
and cover require to be operated upon, a pin should be fixed so as to
prevent the latter from rotating in its groove; so that before finally
removing the barrel from the lathe, the cover can be put in position to
have its center accurately adjusted with a long pointed graver.
=503.= =A Barrel That Does Not Run True.= The remedy for this has just
been indicated: enlarge the holes and rivet in them bushings that are
either plain or have only very small holes. The two holes can then be
accurately centered with a slide-rest and cutter of the requisite form.
[Illustration: _Fig. 233._]
It is a very simple process, and yet there are some workmen who, either
from not possessing a lathe or ignorance as to how it should be used,
set the barrel on a screw arbor, and, after having topped the teeth,
round by hand those teeth which have been touched. This method of
procedure is longer than the former and gives results that are worse;
moreover, since the screw-arbors are rarely themselves true, especially
in regard to the cones, which will be found to have a play on the axis,
it is far better to set the barrel in cement on an arbor of the form C,
Fig. 233, on the center pin of which the barrel-hole fits without play;
the middle of plate C must not be too thickly coated with cement.
=504.= =Barrel Out of Upright.= Several methods may be resorted to for
adjusting a barrel that does not turn flat on its axis. Assume that the
holes are not too large, for it has just been shown that by bushing
the holes and truing them on the lathe, it is always possible to ensure
that a barrel shall be true on its axis.
To true it without renewing the holes, first try turning the cover
round in its groove by successive short stages, and test its truth each
time; the arbor being clamped in a pair of sliding tongs and a card
held close to the teeth. If, after the entire circumference has been
tested, no point is found that satisfies the requisite conditions, the
edge of the cover must be gently hammered (a piece of silver paper
being first laid on the anvil so as to avoid marking the gilding) on
the side at which the teeth pass farthest from the card and the effect
of the operation must be tested. This hammering should be done very
carefully and little at a time, and if too great a strain is put on the
cover to force it into the groove, some metal must be removed from the
side opposite to that at which the hammering occurred. Hence, if the
one side is too much extended in the first instance, so that a large
amount of metal has to be removed from the opposite side, the operation
is liable to be unnecessarily long and difficult. It is hardly
necessary to observe that we are here referring to the modern form of
going-barrel, in which the cover is on the opposite side to the teeth;
in the older form, where the reverse is the case, the opposite edge of
the cover must be hammered.
Sometimes a barrel that runs true on its arbor is found to incline when
mounted on the plate: such a fault is due either to the barrel holes
being too large or to the sink that receives the ratchet not being
parallel to the plate. This sink must be trued in the lathe while in
position, screwed to the plate of the watch.
[Illustration: _Fig. 234._]
=505.= =To Adjust a Post or Curb in Position.= Make a small punch, a
front and side elevation of which are shown at _p p_, Fig. 234; harden
it and let it down to a yellow temper at the point. Now fix a flattened
ball of lead in the vise, the upper surface of which is so formed that
the portion of the barrel that is to receive the hole for the post may
rest securely. There is no necessity for the entire barrel to rest on
the lead. Place a small piece of mainspring, _q_, within the barrel
against the circumference, where it will be maintained by the punch
_p_, which will also hold the barrel steady on the lead block. Then
give a moderate blow with a heavy hammer on the head of the punch,
forcing its point through the barrel.
A burr will be produced outside the barrel, while there will be a
corresponding depression within, especially in front of the hole. To
secure clean edges, pass a file over the external projection, but only
sufficiently to remove its crest, and, resting the inside of the barrel
on a lead block, drive inwards the metal that projects; then pass the
punch through in a direction opposite to the first and of course with
less force. Remove the burrs and repeat the operation first on one side
and then on the other with gentle blows of the hammer, removing the
punch by hand. Finish with a very fine file, which will entirely remove
any external burr round the hole, and one cut with a slide-rest cutter
in the inside, followed by charcoal and oil.
A watchmaker that has never performed this operation will do well to
experiment with the punch on a small plate of brass, or, still better,
on a worn-out barrel.
To insert the post, coil up the mainspring in the winder so as to be
able to introduce a slightly conical piece of steel or brass between
the two last turns of the spring and near to the hole. Place the post
in position and hold it and the spring while the wedge that keeps the
coils apart is removed. If the opening thus secured was found to be
insufficient, it might be increased by introducing a screwdriver, which
is held down until the post is inserted. The making of this curb, shown
at _b_, Fig. 234, will offer no difficulty.
[Illustration: _Fig. 235._]
=506.= =Stopwork.= If the pitch circles of the finger-piece and
star-wheel of several Geneva stops be measured, it will be seen that
three different proportions may exist (Fig. 235), in which the former
is less than, equal to, and greater than the latter respectively.
When the finger-piece has a greater diameter, as at _d_, it will oppose
an increased resistance to the hand in winding, but the direction of
its pressure against the stop will be much below the center of rotation
of the star-wheel, because the finger is necessarily very short.
When the finger-piece is very small, as at _a_, there will be less
resistance opposed owing to any want of freedom of the star-wheel,
and the pressure against the stop will be more nearly tangential, the
finger being relatively long; but more care will be required in the
construction and, for a given force applied to the key in winding,
there will be a proportionately increased pressure against the
star-wheel axis.
Inconveniences thus increase in proportion as either piece is enlarged
as compared with the other, and the best proportion is secured by
making the two diameters equal, as shown at _c b_.
The stud on which the star-wheel rotates should be cut square or,
preferably, slightly conical downwards.
=507.= =To True a Star-Wheel.= The form of a star-wheel can be adjusted
on the lathe, on the tool shown in Fig. 208, using a cylindrical
mill-cutter and adding a stop so that the branches of the tool are
always brought to the same distance apart.
Star-wheels can be bought of the material dealers, but they are not
always equally divided; indeed, some exist that have been merely
punched in the punching press. Hence it follows that many of them are
characterized by at least one of the following faults: teeth of unequal
length, or with their concavities of unequal form.
[Illustration: _Fig. 236._]
When the teeth are well formed and finished at their ends, but of
unequal length, this arises from the star-wheel having been badly
centered during the operation of cutting; it must then be re-centered.
Take a small brass plate H, Fig. 236, and drill a hole at its center,
with a notch at the edge, _a_, to receive the convex tooth without
shake. Now place the plate in the lathe and turn out a sink to receive
the star-wheel and hold it firmly. The convex tooth will then drop into
the notch and the wheel should project a little above the face of the
plate. Now release one dog, and, having gripped with it one tooth of
the wheel, take a fine-pointed graver and true the central hole and the
sink that receives the screw head, taking care only to remove a small
quantity of metal at a time.
If the workman has not considerable experience in using the lathe and
fears a derangement in releasing and again tightening the dog, he had
better remove the plate, cement the star-wheel in position and replace
it, when it can be re-centered with the pump-center.
=508.= =To Make a Finger-Piece.= After having drifted the square hole
in the center of a steel disc of suitable dimensions, and traced
out a line to mark the circumference of the disc and the end of the
finger, drill two holes a little beyond this line, leaving such a space
between them as to ensure that the base of the finger shall possess
sufficient strength; but these holes should be drilled so far in
towards the center of the disc that freedom is left for the corners of
the star-wheel teeth during its rotation. The head of the finger is at
first left so as to exactly fit the spaces of the wheel without play,
this being subsequently given with a fine file and in the smoothing.
File the circumference all round so as just not to touch the line
traced out; then, putting the disc on an arbor, hold a fine _barrette_
file against the edge, and cause the arbor to oscillate backwards
and forwards, the file coming in contact alternately with each side
of the finger. This smoothing of the rim will materially facilitate
and abridge the final work with the graver. The corner of the rim on
one side of the finger having been finished off with the graver edge,
reverse the arbor between its centers to treat the other corner in a
similar manner. A finger-piece made as here explained will be found to
be very true.
Some watchmakers, when it is possible, finish the circumference after
it has been adjusted on the barrel-arbor itself; but as a rule this is
not necessary.
The slit that receives the pin may be cut as follows: File a square
piece of brass to fit the hole in the finger-piece, cut a notch across
the end with a screw-head file, and insert it in the square hole.
Having centered a flat cutter, the thickness of which is equal to that
of the slit to be cut, on a taper arbor, place this in the lathe;
resting the brass horizontally on the T-rest (which had better be at
the back of the lathe, so that the progress of the operation may be
more easily observed) and present the notch to the cutter.
=509.= It will be understood that the foregoing details relate to the
method to be adopted in making the finger-piece by hand, but it is very
easy to arrange an addition to the ordinary lathe, with or without a
throw, for rounding or truing the circumference with great rapidity.
Having mounted a circular mill-cutter on an arbor in a chuck, as seen
at R, Fig. 233, replace the =T=-rest by an upright that has a shoulder,
and is truly cylindrical, and of a diameter to fit the support without
shake; the finger-piece, D, is fixed to its upper end by a cone and
nut, as in the screw-arbor, or by any other means. A lever _l_ is
adapted to the vertical rod, so that it can be rotated between two
stops on the lathe-bed; such stops are, however, not always needed,
because by employing a thick cutter that is smooth on the face there is
no danger of damage to the finger. At the same time, if there are no
stops, considerable care is requisite in the smoothing and polishing to
prevent the sides of the lap touching the finger. This can be polished
afterwards in a very short time by using a lap that has been turned
on the edge to fit the notch. It is useless to enter into further
particulars, as the little appliance or one of an analogous description
can be easily made.
The apparatus shown in Fig. 195, and described in article =402=, could be
employed for such a purpose.
=510.= =To Make a Clock Barrel.= A strip of soft brass, thicker than
the circumference of the drum is intended to be, is coiled into a
circle rather less in diameter than the required barrel, on a cylinder
of hard wood, either by pressure between the jaws of a vise, or with
a mallet or hammer. The two edges, after being carefully cleaned, are
soldered with silver solder or brazed, while they are held in position
by a piece of binding wire wound round the drum.
Placing this ring on the nose of a beak-iron, harden it by gentle
blows, so as not only to harden the brass, but also to increase the
diameter and make a true cylinder.
Chuck it on a cylinder of hard wood in order to turn the two ends
square, and form the edge that is received in a groove cut in the
bottom of the barrel; the bottom is then soft soldered in position. In
the older barrels that contained very strong springs, it was often the
practice to leave tongues projecting round the drum that entered holes
in the bottom and were riveted on the other side.
The barrel may be cemented to a large wax chuck that has as its center
a short arbor tapped and provided with a washer and nut, or it may be
gripped by its base in the universal head, and the surfaces, etc.,
finished.
Some of the details given in regard to a watch barrel are applicable
here.
The drum is now no longer made by bending a strip of brass, except in
country towns, because brass tubing is always to be obtained in cities
at metal warehouses, which only needs to be cut into rings of the
requisite length.
=511.= =To Make a Barrel-Arbor.= If the metal is in the rough and has
the scale on, it must be cleaned either on the stone or with acid.
The following method of procedure has been proved in practice to be
expeditious:
When the arbor has been turned to shape with the graver, smoothed, and
almost polished, it is placed in the barrel and should rotate when in
position, but with considerable friction. Then make the two squares as
explained below (=513=); and, after smoothing that which receives the
finger-piece, set this latter in position on the arbor and see that
it does not descend quite to the shoulder. Then replace it by a worn
out finger-piece, or by a copper disc that is cut so as to allow of
the insertion of the pin in exactly the same position as is required
by the finger-piece to be definitively used. It is then easy to drill
the pin-hole from either side of the square and to smooth it with a
fine broach. Each time that the arbor has to be inserted in the barrel,
great care must be taken to remove any burr, as it might damage the
barrel holes.
Before hardening the arbor, cut in it two grooves of moderate depth at
the points at which the ends must be broken off. Such a practice has
two advantages: 1. The two waste points of the arbor can be removed
and each end partly formed without employing a file, an arrangement
whereby it is possible to maintain in the arbor a maximum of hardness,
at least at the winding end. 2. If the arbor is distorted, it will not
be in the body, but from the points at which these cuts are made. If
any distortion occurs, the blow-pipe jet can be directed on the points,
which are then removed with a file before the final polishing.
=512.= To harden the arbor, place it in an iron tube and surround
it with powdered charcoal which is pressed down, having previously
been well dried. When the whole has been heated to the requisite
temperature, throw it into water, and, if the precautions already
explained under hardening are adopted, the arbor will be found to be
smooth and clean and without either scales or blisters on its surface.
Clean and polish it; this latter operation will give the proper freedom
to the pivots, although it often happens that a touch with a broach is
required in the two holes.
[Illustration: _Fig. 237._]
The bevelled groove within the ratchet teeth is polished by rotating
the arbor while a small steel plate, perforated at its center and of
the form shown in plan and section at Z, Fig. 237, is held by the hand
against the groove. The shoulders can be easily and rapidly polished in
the tool represented in Fig. 44.
[Illustration: _Fig. 238._]
=513.= =To Make the Squares. To Make Drifts.= The tool shown in Fig.
238 is used. On the plate P, which is at right angles to the foot S,
is fixed a frame that carries two hard steel rollers, _c_ and _d_, the
edges of which are extended to form a guide.
A bent finger _b_ is hinged on a screw on the side of the plate, and
has a hole _j_ drilled in it, which is continued for a short distance
into the plate P.
The following is the method of using the appliance: Fix to the arbor
a disc, indicated by dotted lines, in the circumference of which are
four equidistant notches to receive the nose of the finger _b_. The rod
S takes the place of the =T=-rest and the arbor is placed between the
centers of the lathe. As S can be raised or lowered to any position
and the runners can be moved laterally, it is easy to bring the point
at which the square should commence to correspond with the line _n
n_. The finger _b_ having been inserted in one of the notches of the
division-plate, reduce the arbor with the file L. Move _b_ to the next
notch, and repeat the operation, and so on with the other two sides.
If there is any danger of the finger not maintaining a sufficiently
firm hold of the plate, a tight-fitting pin can be inserted in the hole
_j_.
At first the arbor should be filed away less than is actually required,
and the only adjustment necessary to ensure this is the raising of S
to a suitable height. No difficulty need be experienced in this, but,
if any doubt is entertained, a screw may be supported from the bed of
the lathe, terminating in a rod that passes through the plate P, as
indicated at _t_ for example, thus securing perfect regularity in the
upward and downward motion of the system.
If a tapered square is required, it will be sufficient to slightly
incline the frame by means of two screws _v i_, placed near its
left-hand edge with their ends resting on the plate P.
=514.= =To Drill Exactly Through the Center of the Arbor.= Of course,
if the old arbor-nut is available, it will afford the best guide
for performing this operation, and, if the arbor is tapped, such a
hole will not be required. But when neither of these conditions is
satisfied, the workman will have two slight difficulties to overcome:
the drilling of the arbor and its nut exactly in the center and
parallel to the plane of the ratchet. By adopting the following method,
he can easily satisfy these conditions:
[Illustration: _Fig. 239._]
=515.= Take a brass disc D, Fig. 239, turned smooth on its two faces.
Enlarge its central hole until the barrel-arbor enters it to such a
distance that a blow of a mallet will drive it up against the ratchet
where it should hold firmly. This disc is chucked on the lathe and a
groove is formed that passes exactly through the center. Ascertain by
means of a douzieme or a thickness gauge whether the thickness of the
disc, measuring from the bottom of the groove to the under side, is
equal to the space between the shoulder of the arbor that corresponds
to the outside edge of the barrel hole, and the point at which the hole
should be drilled. If the thickness is excessive, diminish it from the
under side; if, on the other hand, it is not sufficient, fit some thin
discs on the arbor, and then force the brass disc to the position thus
determined upon. It is hardly necessary to add that when this is done,
holes must be drilled to some depth on either side of the arbor, using
a drill that does not shake about in the groove although quite free and
inclining slightly downwards so that the hole shall not be above the
point determined upon, namely, the bottom of the groove. Continue the
drilling until the two holes meet, the drill being maintained, during
this part of the operation, parallel to the face of the ratchet.
[Illustration: _Fig. 240._]
=516.= If the workman is not provided with a tool for cutting the
groove exactly in the axis of the disc, the accuracy that is so
essential can be ensured as follows: A brass rod G, Fig. 240, is
divided into four at the end as near the center as possible by means of
a fine saw or a file that only cuts with its edge, which will be used
to form the groove. Set the rod G in the lathe, a center of the form
_f_ being inserted at _b_ where the slits cross, and turn down the rod
G _b_, although only a little metal should need to be removed, until
it enters the hole in the brass disc and projects a short distance on
the other side. It then only remains to insert in one of the notches
of G _b_ the cutting file or the saw previously used, to form a groove
on the surface of the disc that passes exactly through its center; it
is to be remembered that the saw, etc., must only cut with its edge,
and should enter the notch with a very slight friction, sufficient to
indicate that it fits without play.
=517.= =The Arbor-Nut.= The usual practice is to make the diameter of
the nut equal to one-third that of the inside of the barrel. With thick
springs of but slight flexibility it must be larger so as to avoid
overstraining the innermost coil, and, conversely, with a very thin
spring it is diminished, rendering the employment of a longer spring
possible. When the nut is too small the spring must be made long, and,
by setting up the stopwork, a coil of the spring can be maintained
always on the nut.
=518.= _To drill the nut along a diameter._ By means of the rod G, Fig.
240, draw a straight line to indicate a diameter of the nut. This line
will serve as a guide for marking two points opposite to one another on
the circumference, round which a circle has previously been traced with
a graver. The points should be marked so deeply as to ensure that the
drill does not displace itself in the initial stages of the drilling;
with a little caution, and using a glass, very little difficulty will
be experienced in ensuring that the points are in a right line. One of
the two following methods may be employed for drilling the nut:
[Illustration: _Fig. 241._]
1. Prepare a brass block of the form shown at _f p f′_, Fig. 241, the
space A being cut away, and the end _p_ provided with large-headed
screws, shown at _v_, _v_, in the plan. The two faces, _f_, _f′_, must
be parallel to each other, and at right angles with the face _p_, a
condition which can be easily satisfied by means of the lathe, the face
_f′_, for example, being turned towards the headstock, and the dogs
introduced into the space A; the opposite face _f_ is then trued with
the slide rest. In the vertical face _a a_ make a round hole, through
which a pointed center passes, being pressed forward by a spiral or
other spring, and the point corresponding exactly with the line _a a_
traced on the face of the brass; of course the axis of this center must
be at right angles to the same line. A small block may be inserted
within the space A to prevent any flexure of the arms.
An inspection of the figure will make clear the manner in which this
little tool is to be used. Having fixed the nut on the face _p_ by the
screws _v v_, so that the two points on its circumference coincide with
the line _a a_, the whole is placed in the drilling tool with the dogs
pressing either on the upper external face or in the space A. After the
block is fixed, ascertain by rotating the uprighting spindle that its
point coincides in all positions with the top mark on the edge of the
nut, and drill as usual. Drill one side, invert the block, and proceed
in a similar manner to drill the other.
The little appliance above described might be simplified by being made
of the form shown at E, which would require to be reversed when the
second hole is about to be drilled.
=519.= =To Polish the Inclined Faces of Ratchet Teeth.= Set the ratchet
in slow rotation by means of the foot-wheel, and bring a strip of
spring covered with coarse rouge and oil against it from the side,
resting the strip on the =T=-rest. In a very short time the teeth will
be rounded and polished. This process is similar to that adopted at the
present day for polishing the inclines of cylinder escape wheels in the
lathe. The position of the polishing spring and its inclination must be
determined upon by trial, so as to make sure that the entire surface of
the tooth is acted on.
[Illustration: _Fig. 242._]
=520.= Another method is to make a small boxwood lap, and arrange it
as shown at M, Fig. 242, so that, when caused to revolve on its axis,
which may be more or less inclined, it is brought into contact with the
ratchet wheel with its axis, as indicated by the figure. The teeth will
cut into the wood, and trace out a helix, as seen at M′, and the lap,
passing successively into the ratchet teeth, will cause it to revolve
rapidly. When the groove is deep enough, apply some coarse polishing
rouge to the surface of the drum; after a few rotations the faces will
be found to be polished.
The arbor and lap may be arranged in either of two ways.
Mount the lap between the centers that carry the cutter in a
wheel-cutting engine and support the barrel-arbor opposite to it in a
vertical direction between the chuck and the bent arm or “gallows” used
to fix a wheel while cutting its teeth.
A watchmaker who is not provided with this tool must chuck the lap in
the lathe, then mount the barrel-arbor in such a carrier as is shown
at _p p_, Fig. 242, and, resting its base on the =T=-rest, hold the
ratchet against the lap, determining the most suitable height and
inclination by trial; this, he will find, can be easily done.
=521.= =To Polish the Circular Groove in the Ratchet.= It takes a
long time to accomplish this by using first, an iron polisher with
oilstone dust, then one of copper with rouge and oil. The operation
can be performed more expeditiously by using an iron runner, as shown
at B, Fig. 243. The end is rounded to correspond with the groove; and
the hole, which is indicated by dotted lines, should be large and
funnel-shaped, so as to avoid contact with the corners of the winding
square when a see-saw motion is given to B in the polishing.
[Illustration: _Fig. 243._]
The arbor being cemented to a chuck in a lathe, hold the end _o_,
charged with oilstone dust or rouge, in the groove, and, while the
arbor revolves, rotate the spindle B in the hand, at the same time
giving it a see-saw motion as above mentioned. A very little practice
will be required to do this.
=522.= =Repairing a Barrel-Arbor.= Cement the arbor _a a_, Fig. 244,
to the lathe chuck, turn down the ratchet, removing its teeth and thus
diminishing its diameter by about a third, as shown at _n n_; then
reduce the thickness to a half, turning it down on the side next to
the winding square, and continue this square down to the flat disc that
remains, taking care that no shoulder is left at the angle between the
two. The arbor is now in a condition to receive the new ratchet which
has to be fitted.
[Illustration: _Fig. 244._]
Adjust a flat ratchet _r r_ like those used on the barrel-arbor of
a fusee watch, which must be of the thickness and diameter of the
original ratchet, so that it exactly fits the winding square; turn a
sink in it, as shown by the dotted line, to receive the disc already
formed; and, if the hole fits the winding square freely but without
play, and this square is carried down to the disc, the dust cap _c c_
will maintain the ratchet in its position as effectually as though it
formed one with the arbor.
By adopting the above method, which does not occupy much time, it is
often possible to avoid making a new arbor when all but the ratchet is
sound; and if this portion should again wear out, the necessary repair
is still further simplified.
We are assured that arbors repaired in the above manner showed no signs
of wear after fifteen years, except that the square in the ratchet was
a trifle enlarged, though not sufficiently to interfere in any way with
the efficiency; moreover, in modern watches, the winding square is
generally long, so that the ratchet can be left somewhat thicker at the
center and a corresponding sink cut in the under side of the dust cap
to receive it.
=523.= =To True a Barrel-Arbor that is Coned Inwards or too Large.=
Cement the arbor firmly to a chuck as shown at C, Fig. 245. With care
it will be easy to make the part _e_ run true. As a rule, but very
little metal requires to be removed to make _e_ cylindrical or conical
in any desired direction, and it will generally be sufficient to finish
by polishing with an iron polisher and oilstone dust or coarse rouge
and oil. Use a narrow polisher that only bears on the end of _e_,
giving it a double movement, straight forward and in a half circle
towards one side; or else use a broader polisher, supporting it on the
=T=-rest. By inclining this, the iron can be prevented from touching
_e_, except near its extremity. It is unnecessary to add that when
the arbor has been made cylindrical or coned in a given direction a
suitable polisher, bearing on the entire length of _e_, can be used.
[Illustration: _Fig. 245._]
Either of the two following methods can be adopted in the place of that
above explained: Support the winding square end of the barrel-arbor in
an eccentric runner; let the opposite end run in a small coned hole
in the end of a steel runner, which must be polished and hardened so
as to prevent the corners of the square that receives the stop-finger
from wearing it away; now apply coarse rouge until the fault no longer
exists and follow with fine rouge to complete the polishing.
If not provided with an eccentric runner, it will be sufficient to take
a tight-fitting key, drive it on with a blow of a hammer and file a
point at the tapped end so as to be in the axis of the barrel-arbor.
Having attached a ferrule to this key, place the whole between the
runners and proceed as explained above.
=524.= =To Renew a Worn Winding Square.= The best plan is to make an
entirely new arbor; but when this cannot be done, as, for example,
on the ground of expense, the following method of repair may be
attempted: Direct the blow-pipe flame on to the square while holding
the body of the arbor in a pair of pliers, so as to prevent its
being over-heated; and round off the corners of the square, leaving
the diameter no greater than is necessary for strength, and tap it
with a screw-plate. Now drill a hole at the end of a piece of round
steel of somewhat greater diameter than the original square, and form
an internal screw by means of a tap made in the same hole of the
screw-plate as was used for the arbor; the end of the tap should be
tapered and with good cutting edges.
If the arbor is the full length allowed by the case, reduce the length
slightly and screw on the small steel spindle, tapped to the right
depth. It must not be screwed quite down to the ratchet, although
intended ultimately to come into actual contact. After having thus
tested it, form the square, which will naturally be rather larger than
the original, and cut a deep groove with the graver at the point where
the square is to be broken off, but, before breaking it, harden and let
down to a blue or violet temper; then smooth, polish, and screw finally
on to the arbor. If this last operation does not result in the square
breaking away, grip the spindle in a vise, and, taking the square in a
pair of long-nosed pliers, break it with a sharp blow. It only remains
to finish off the end in a screw-head tool.
THE MAINSPRING.
=525.= A free and uniform action of the mainspring is one of
the primary conditions that have to be satisfied for ensuring a
continuously good rate.
=526.= _To make the eye in a Mainspring._ Every watchmaker knows that
this is commonly done by means of a mainspring punch; but in its
absence a hole can be made by hammering a pointed punch one or more
times through the end of the spring after it has been softened, and,
after filing away the projecting metal, the hole is broached out or
enlarged with the point of a graver and finished with a rat-tail file,
taking care that the corners are rounded off so as to avoid the risk of
cracks.
=527.= _To reduce the height of a Mainspring._ This and the following
method are only to be resorted to when a new spring cannot be obtained.
Introduce the spring into a barrel of less height than itself and wear
the steel away by rubbing it on a hard surface charged with oilstone
dust, keeping it constantly rotated between the fingers. When the
reduction is sufficient remove the spring and draw-file it, so as to
round off the two edges; then clean the entire surface.
=528.= _Selecting a Mainspring: Adapting it to a Fusee._ The spring
that is characterized by the most uniform uncoiling and the least
difference between the force exerted when fully and only partially
wound up will generally secure the most constant rate. In selecting one
for a going-barrel watch, or in adapting to a fusee, the adjusting rod,
shown in Fig. 246, and described in article =530=, is used.
THE FUSEE.
=529.= At the outset, we would state the three characteristic
properties of a fusee that have led to its adoption and retention in
high-class watches and marine chronometers: 1, it equalizes the motive
force; 2, it enables us to use a _tapered_ mainspring, in which the
uncoiling takes place in the most advantageous manner possible; and, 3,
it secures a longer period of going.
[Illustration: _Fig. 246._]
=530.= =To Adjust a Fusee to Its Mainspring.= Set the barrel and fusee
in position in the frame, with the mainspring and chain carefully
hooked in their places, and the former set up about half a turn, and
grip the fusee square in the clamp, _d n_, of the adjusting rod, shown
in Fig. 246; then wind up the mainspring by rotating this lever with
the hand until arrested by the stopwork. Now slide the weight _m_,
which is held by friction and a light spring, along the rod until a
point is reached at which the lever just neutralizes the force of the
mainspring, so that the whole rests in equilibrium when left to itself.
Rotate the rod backwards by half turns at a time. If equilibrium is
maintained to the end, the fusee is well adjusted. But when this is not
the case, it will be found that the weight of the lever is too great
or too small; showing that the radius of the fusee is either too small
or too great. Adjust the lever so that it balances with the radius of
the fusee, which is thus shown to be most deficient, and at all other
points along the thread of the fusee more metal must be removed to an
extent indicated by the experiment.
When not provided with a fusee engine, it is a common practice to use
the ordinary lathe, and an equaling file smoothed on its two faces; or
a templet might be adapted to the =T=-rest of such lathe.
If the irregularity observed is but slight, it is advisable not to
touch the fusee; because, in the great majority of cases, an equipoise
can be arrived at by altering the degree to which the spring is set up.
Thus, if the weight is too heavy for the lower coils of the spring, set
it up more, so as to increase its tension; in the converse case, of
course, it must be let down. By trying several springs, especially if
they are of different manufacture, it will very often be found possible
to secure a sufficient degree of uniformity without there being any
occasion to re-cut the fusee.
CHAIN.
=531.= =To Ease a Chain.= When the links are rusty or not sufficiently
supple, the chain should be placed in oil and left there for some hours
at least. Round off the edge of a boxwood block, cut a groove across
this edge, and clamp the block in a vise; then place the chain like a
saddle in the groove, so that it hangs down on either side. Applying
oil liberally to the wood, take an end of the chain in each hand, and
pull it backwards and forwards in the groove, renewing the supply of
oil at intervals. When perfectly flexible, the chain must be cleaned
with benzine, or, after soaping, wash it in water and leave for some
minutes in alcohol. After being dried, it is dipped in fine oil and
dried in a clean linen rag free from fluff, pressing the rag against
the edge. A chain treated in this manner will be found to remain supple
for a long time, and it will not be liable to rust.
=532.= =Riveting a Hook, Etc.= When riveting either a hook or link to a
chain, it is very necessary that the end of the rivet be cut or filed
quite square; for, otherwise, the blow of the hammer will bend the
rivet, so that the chain will not be square on the barrel, neither will
the riveting be firm.
WHEELS.
=533.= =To Rough Out a Wheel.= The sheet brass having been prepared
in the manner indicated in article =103=, one face is smoothed with a
file, followed by oilstone dust; the plate is then set up in the lathe,
to true the other face with the slide rest. On the smoothed face trace
out the rim and the crossings. These latter can best be marked out on
the dividing plate, or _grammaire_, already explained in article =343=.
[Illustration: _Fig. 247._]
After drilling the small holes, _a_, _c_, etc., Fig. 247, at the
corners, cement the wheel to a plate that is perforated to permit the
use of the pump center, and remove the metal between the crossings by
first turning the sinks indicated by the shaded disc _s_ with the slide
rest, and subsequently cut the groove _i i_. Now center the wheel in
the lathe, and trace the arcs _a c_ with a fine graver, moving the
face-plate backwards and forwards in the manner referred to in article
=364=.
Remove the wheel from the plate, and finish off the spaces with a
file. Two files will be needed for forming the angles; one a flat
barrette file, with the corner beveled off and smoothed to nearly a
right angle, to go against the rim of the wheel; and the other a taper
file, with faces of the same curvature as the inside of the rim, its
two edges being inclined at rather more than a right angle and smoothed
carefully. If these simple precautions are not taken, there is a risk
of cutting through the arms or making them too narrow.
Many of the details in the following article, although specially
relating to a balance, will be found applicable to the construction of
other wheels.
=534.= =To Make a Plain Balance.= The round plate of which the balance
is to be made must be hammered with the greatest possible care, and
of a thickness but little greater than that of the finished balance
(=103=). Smooth one face and cement it either to a perforated plate
through which the pump center can reach the balance (if the universal
head is to be used), or on the chuck of an ordinary lathe, or on
the wax chuck C, Fig. 233. Hollow the middle portion with the slide
rest cutter or hook tool, according to the kind of lathe used; but,
whichever it be, it must be very well set, and only remove a small
portion at a time. The application of an excessive pressure will
produce a kind of rolling action, which will induce a tendency in
the arms to bend. Remove the metal between the rim and boss until
its thickness is diminished by about a third; smooth this surface
carefully, finishing with a piece of charcoal. The disc is now ready
for crossing out.
Place it on the dividing plate (see article =343=) to mark out the
three arms, and remove the metal between them, either in the lathe, as
explained above, or by drilling a series of holes parallel to the arms
and rim. These holes should be so arranged that they can be enlarged
with a fine-pointed graver (while the balance rests on a flat wooden
block or is cemented to it), and a turn with a sharp edged broach, or
the passage of a thin rat-tail file should be sufficient to separate
the useless metal. As a rule, the series of holes is drilled with the
disc held against a wooden block, but the burrs produced on the under
side by the drill prevent it from being maintained flat, unless they
are removed after each hole is drilled, and this might occasion a
distortion of the disc. It would, perhaps, be better to cement the
rough balance to a sheet of zinc; the color of the shavings would
suffice to indicate whether the hole was through.
The arms and rim must be made smooth and even with nicely formed
crossing files, the edges of which are smoothed to the most convenient
angle, as already indicated.
In filing the crossings the balance should rest against a small block
in the vise, and they are rounded while resting in a groove at the edge
of a similar block, specially shaped for the purpose. This block is
also useful as a support in finishing the angles between crossings and
rim.
The under face of the balance is smoothed with oilstone dust; and the
arms by drawing the polisher along them while the balance rests on a
flat block; it is then cleaned and fitted on a very true arbor, as
A, Fig. 233. This should pass through the center hole of the balance
without play after a broach has slightly enlarged it, and the balance
is clamped by a cap and three screws, _j_. It only remains to set the
arbor in the lathe and polish the rim, first turning it to a half
oval if desired. In the latter case the rim, after being smoothed, is
polished first with coarse rouge on hard pith, and subsequently with
fine rouge on softer pith.
=535.= If the arms of a balance are found to be too long, so that
they curve, the rim must be lengthened by hammering with the greatest
possible care; the inside and outside of it must then be trued on an
arbor of the form A.
The boss at the center will be found thicker than is desirable; its
height can be reduced with the balance merely adjusted on a smooth
taper arbor, but it is necessary to observe that the balance and
arbor must not be adjusted to each other by pressing or by rotating
the balance with the rim held in the fingers. It must be pushed on or
off the arbor by applying pressure at the center of the boss on one
side or the other with a piece of hard wood resting firmly against the
=T=-rest, while you cause the arbor to rotate.
Instead of the form of arbor shown at A, a screw arbor might be used,
with its cone pressing against a cap, but the balance must always be
carefully adjusted on the arbor, and this latter must run perfectly
true.
=536.= =To Make a Number of Identical Wheels.= If it is desired to
make a number of brass wheels of the same size and shape, the workman
will find it much to his advantage to employ the punching machine.
By adopting the following method he can make his own punches and
bed-plates.
[Illustration: _Fig. 248._]
With a view to secure same length in the matrices that are used
for forming the crossings, without augmenting the difficulty of
construction, proceed thus: Each of the pieces V, V, Fig. 248, consists
of two parts: 1. The star-piece, _a c b d_, of three, four, five or
six arms, according to the number of crossings of the wheel. 2. The
collar, V. The star-piece is of the same length as the collar, and is
made in the wheel-cutting engine in the same manner as the leaves of
a pinion. The punches, of which one is shown at P, are fitted by hand
to the recesses of the star-piece, and then cemented in position; the
whole is then chucked in the lathe and turned as one piece, so that
its diameter is slightly greater than the interior of the collar. Now
harden the star-piece, and temper it to a blue color. When cold harden
the collar V _v_, and temper it to the same degree, but, while expanded
by the heat in tempering, introduce the cold star-piece and drive it
home. By proceeding in this manner, no subsequent hand fitting will be
required. V _n_ must not be hardened.
Tools for punching the crossings of wheels are sometimes made on this
system in which the disc of brass is fixed to a support that can be
made to revolve by quarters of a revolution at a time, and a single
punch serves to remove the metal by four separate operations. But as a
rule it is better to use four punches together.
=537.= =To Repair Wheels.= When the teeth of a wheel are damaged, the
only possible remedy is to provide a new one. If, however, a single
tooth is broken, the following method can be adopted, on an emergency,
for inserting a new one:
[Illustration: _Fig. 249._]
=538.= _To insert a new tooth in a wheel._ Cut a small notch in the
rim of the wheel, shown at _a_, Fig. 249, which should be dovetailed
if possible, and the two sides spread out slightly from the upper
towards the under side, as indicated at _c c_. Cut a small piece of
well-hammered brass, of the form B, so that the part _d d_ fits exactly
into the notch in the rim. Now invert the wheel and grip it near to
_a_ in a pair of long-nosed pliers, which must be held in the vise.
Moisten the inner faces of the notch with soldering fluid and, placing
B in position, put particles of solder round its edge; holding the
lamp beneath the nose of the pliers, the solder will presently melt,
and a drop of the fluid should be added to facilitate its running into
the joint. Cool the wheel and wash thoroughly, first with water and
subsequently with alcohol.
It only remains to file both faces smooth and level with the rim of the
wheel; then shape the tooth carefully.
By introducing B from the side opposite to that which is visible in
the watch, and sloping the faces _d d_, to a less degree than _a_, the
inverted wheel will present a recess to receive the solder; so that, on
looking at the upper surface, at which the edges fit very closely, the
joint will be scarcely visible.
=539.= _To true a wheel._ When the teeth are found to be in good
condition, but the wheel does not run true, or one or more of its
arms are strained, the fault can be corrected, in a case of absolute
necessity, as follows:
Remove the pinion from its wheel. Enlarge the central hole in the lathe
and rivet or solder in it a brass ring that is slightly thicker than
the wheel, and perforated with a smaller hole than that required for
the riveting. Now center the wheel from its circumference; increase the
central hole with the slide-rest cutter, and turn down the two faces
of the ring level with the wheel. Rivet the pinion in its place, after
testing the truth of its riveting neck, when the wheel should be found
to turn both true and flat.
If the wheel under repair is likely to be subjected to much force, at
least two small notches should be left in the enlarged hole in the
wheel to receive corresponding projections in the brass ring.
=540.= If the _crossings of a wheel are broken_ and the wheel cannot
be replaced, it must be chucked in the lathe and the arms turned out
with a graver, the inner edge of the rim being at the same time turned
circular, and a step turned on this edge where the metal is to be left
of half its original thickness.
Take another wheel of the same size and thickness, or a plain disc, and
turn it of the same diameter as the outer ridge of the step; reduce its
thickness at the edge by one-half and a disc will thus be obtained with
a ridge round the edge corresponding exactly with that of the wheel,
and the one will fit in the other. They are, of course, soldered in
this position, care being taken to prevent the solder from reaching the
teeth, and the old wheel will thus be provided with a new interior.
If the disc is made to fit closely on the upper side, a wedge-shaped
ring being left to receive the solder in the manner explained in
article =537=, the joint will be scarcely perceptible on the exposed
face, even with a glass.
In repairing delicate wheels in any way it is a good precaution to
cement the rim to the edge of a hole in a brass plate, so that only the
arms or other part to be operated upon is exposed.
=541.= =To Make a Stem-Wind Wheel.= We will suppose that the old wheel
is available as a pattern; if it is not, the several dimensions must be
ascertained by calculation in accordance with the laws of depths.
[Illustration: _Fig. 250._]
Prepare a thick plate, and drill a central hole, fitting a steel pin
into it as shown at _o d_, Fig. 250. The diameter of _d_ must be
exactly the same as that of the pump-center in the universal head. Fit
the wheel-blank R to the pin _o_ without play, and cement it to the
plate. Remove the pump-center and insert _d_ in its place, clamping
the plate P firmly against the face-plate by the dogs. By using
well-sharpened gravers or cutters, the wheel may be rapidly shaped.
The pin might be forced in from the under side to the level of that
face of the plate; and if it were perforated as shown by the dotted
lines, it might be centered by means of the pump. Or the plate P might
be made circular and centered from its circumference.
=542.= To cut the teeth on the circumference the wheel need only be
fixed on the chuck of the wheel-cutting engine as usual by means of the
steel cone. The crown teeth are cut while the wheel is firmly cemented
to a pin-chuck like that used in turning it.
Other keyless wheels can be made on the same principle, and such
modifications as may be necessary experience will suggest. Sufficient
information in regard to wheel-cutting has already been given in =397=
and following articles.
PINIONS.
=543.= =To Make a Pinion.= At the present day pinions of all sizes can
be obtained of the material dealers, so that it is very seldom that a
watchmaker is obliged to make one for himself.
In an emergency, however, he can adopt the following method for making
one out of the ordinary drawn steel; but it should be added that, in
all probability, some practice will be needed before success is arrived
at. Cut a length of steel wire of suitable diameter about two-thirds as
long as the files that are to be used for shaping the teeth. Turn it
down to form the axis, leaving a block near each end equal in length to
the required pinion, as if three pinions were to be made on the same
staff. Then cut and round leaves on all, keeping the file always in
contact with a leaf of each pinion. By proceeding thus the sides and
roundings of the leaves will be maintained parallel to the axis, and
there will be no risk of the pinion being barrel-shaped, as is nearly
always the case when a short pinion is held in the fingers or rested on
a block in the vise.
Proceed in the same manner in smoothing and polishing, using pieces of
some close-grained wood, such as walnut.
It is much easier to make the pinion of the required form by means of
a revolving cutter in the lathe, if the workman is not provided with a
special tool for the purpose: the arrangement of the lathe is described
in article =402=.
In some factories the leaves are cut in two operations: a cutter with
plain fine saw teeth divides the circumference into the requisite
number of equal parts, the leaves being subsequently made of the
correct shape by a special cutter, the method of making which has
already been very fully explained in articles =417-435=.
=544.= =To Determine the Size of a Pinion.= The following table is
usually employed for this purpose. See also =562= and the following
articles.
To give the approximate diameter of a pinion, the pinion caliper should
include:
For 16 leaves, 6 full teeth; that is to say, measuring the distance
between the two external faces;
” 15 ” rather less than 6 teeth, or 5 teeth, and just beyond
the point of the sixth;
” 14 ” 6 teeth, measuring at the points.
” 12 ” 5 teeth, measuring at the points (or rather 4½ teeth);
for a clock-wheel, 5 full teeth;
” 10 ” 4 full teeth;
for a clock-wheel, 4 _squared_ teeth;
For 9 leaves rather less than 4 full teeth, or 3 full teeth to the
point of the fourth;
” 8 ” 4 teeth, measured at the points, minus a quarter of a
space;
” 7 ” rather less than 3 full teeth;
for a clock-wheel, 3 full teeth, plus a quarter of
a space;
” 6 ” 3 teeth, measured at the points, or rather more;
for a clock-wheel, 3 full teeth.
It is important to notice that these measures can only be regarded as
a first approximation, and it is only by actual trial in a depth-tool
that we can be certain that a pinion is correctly sized. By taking the
measures in a micrometer, or other accurately divided gauge provided
with a vernier, the work of selecting will be much abridged; but how
long will it be before the generality of watchmakers will make use of
these convenient appliances? The well-known wheel and pinion sector,
although convenient, is not equal to them in point of accuracy, and is
affected by an error in measuring a chord, not a true diameter of the
wheel or pinion.
=545.= =To Increase or Decrease a Pinion.= The pitch circle of a pinion
may be increased by reducing the thickness of the leaves in such a
manner that their flat faces are continued further on to the rounding;
conversely, a pinion may be decreased by carrying this rounding farther
down towards the base of the leaf.
=546.= =To Decrease a Pinion Without Removing the Wheel.= Some
watchmakers recommend that the wheel be removed from the pinion,
and, after the necessary reduction has been effected and the leaves
re-polished, again riveted on the pinion-neck. Very few workmen,
however, can do this well, so that after the operation the wheel is
seldom found to run true. If a new pinion cannot be procured, the old
one must be reduced.
When a pinion that is too large is replaced by one that is smaller, it
is necessary to take care that the hole in the wheel is well centered
and not too large; in either of these cases it must be enlarged and
bushed after being centered by the circumference.
=547.= =To Polish Pinion Leaves Mechanically.= It was formerly the
custom to polish the leaves of a pinion, holding it on a block or
between two fingers and traversing a strip of metal with oilstone dust
backwards and forwards in each space for the smoothing, and a similar
strip of walnut wood (with rouge) for polishing.
This method has long been abandoned in factories, where all pinions are
polished in a machine.
We will proceed to explain a simple arrangement for polishing pinions
in the ordinary lathe, but it is advisable first to describe one form
of tool that is actually in use on the large scale for this purpose.
The two only differ in their dimensions.
=548.= _Pinion-polishing Machine._ A frame B B, Fig. 251, supports
at its upper end an =H=-shaped piece, of the same form as the
cutter-holder in an ordinary wheel-cutting engine; but the arbor,
instead of carrying a cutter, is provided with a wooden drum R. On the
base of the frame is a plate P, which can be fixed by the screw E,
and carries a second plate _p_ to serve as a bed for the slide, which
supports the pinion to be polished freely between two brackets _a_,
_a_. The plate _p_ can be set a little oblique and clamped by the screw
_v_.
[Illustration: _Fig. 251._]
The machine acts as follows: Present a corner of a pinion-leaf to the
circumference of R (which is caused to revolve by a cord passing round
the pulley _n n_), the axis of the pinion being not quite at right
angles with that of the drum, in order that the groove formed in the
soft wood may resemble the thread of a screw, and so cause the pinion
to revolve. When the groove is of sufficient depth, apply rouge if
operating on a small pinion, and emery for a large one: after a few
turns of R, the slide carrying the pinion being at the same time moved
backwards and forwards, the pinion will be found to be polished. A
better surface can be obtained by using flour emery.
The steel wheels of keyless work can be polished in the same manner.
=549.= The spindle of the screw E passes through a rectangular slot in
B in order that the slide and its support can be moved parallel to the
axis of R.
The grain of the wood must be at right angles to the axis of rotation
of the drum, and a wood that is non-fibrous is preferable. It must
evidently not be too hard, and, if too soft, the thread formed on its
circumference will get rough, and often will suddenly change position.
When the entire surface has been worn it must be re-turned smooth and
cylindrical. The larger a roller is, the quicker it will polish and
the less it will wear. Moreover, it will render a proportionately less
amount of motion of the slide necessary. The root of the walnut tree is
especially sought after, but, when this cannot be obtained, other woods
can be used.
In factories where clock pinions are made, thin discs are employed
in place of the drums. They are at least a decimetre (4 inches) in
diameter, and very narrow at the edge, and can be re-turned with a
graver when worn without being removed from the tool, if a =T=-rest be
fixed in some convenient position.
The screw _d_ is for limiting the descent of the drum, but some workmen
prefer to dispense with it, and, instead, hold the frame C C in the
hand, pressing it gently against the pinion. They urge that the wood
is never of the same degree of hardness round its circumference, and
therefore must of necessity wear irregularly; by holding C C in the
hand the pressure on the pinion can be more evenly adjusted, as it is
possible to feel at once whether the drum is polishing or scratching.
The inclination of the slide to a plane at right angles to the axis
of R is measured by the pitch of the screw formed on the drum. But in
practice no special precautions are taken, and it is only necessary to
incline the slide slightly to the right or left, until the pinion is
found to revolve freely.
The drum may be from two to three inches in diameter, and, in order to
ensure the same degree of hardness throughout the entire circumference,
it is a good plan to make the drum of a series of wedges cut so that
the grain in all radiates from the center. Beautiful polished surfaces
are obtained in this manner.
[Illustration: _Fig. 252._]
=550.= _To polish a pinion in the ordinary lathe._ Various methods may
be adopted, but the following is one of the commonest:
Support the pinion between the two centers _b_, _d_, of the
pinion-carrier shown in Fig. 252, the form of which will be evident
without explanation. Rest this carrier by the portion M against the
=T=-rest, pressing it against the drum at the same time with one
finger. Rotating the drum first by hand, make the pinion cut a groove
varying the inclination until it is found to be correct, and, when
sufficiently deep, charge with polishing material, and rotate it with
wheel, at the same time moving the pinion-carrier backwards and
forwards endwise. A little experience will give the requisite skill.
If the pinion is not held at a sufficient inclination it will scrape
and will not revolve. If too much inclined, only the roundings of the
leaves will be polished, the sides being left untouched. A well-formed
groove will last for a long time.
=551.= =To Tighten a Cannon Pinion.= If it is simply slack it will be
sufficient to increase the diameter of the set-hands arbor as described
in article =336=. But if the cannon pinion is in the habit of working off
this arbor when setting the hands, the arbor can be tapered a little
downwards; or proceed as follows:
[Illustration: _Fig. 253._]
Drill a hole in the square that receives the minute hand in the
position shown at _a_, Fig. 253, and also indicated by dotted lines at
_c s_; now turn a groove round the arbor, also shown by dotted lines,
at the point _n_, to correspond with the hole _a_. Insert a pin in this
hole, filing it off smooth with the surface at the side at which it
enters, and nearly level at the other side, to be hammered over just
sufficiently to prevent the pin from working its way out. The cannon
pinion will now be found to turn with the requisite degree of friction,
and without any tendency to work up. It will last all the longer if
both the pin and the groove in which it works are polished.
SET-HANDS SQUARE.
=552.= =To Make a Set-Hands Nut.= This is a small square nut pinned to
the pivot of a solid cannon pinion that projects beyond the top-plate
in some watches after passing through a hollow center pinion. This
construction has been latterly discontinued, but it may be well to
explain the mode in which such a nut can be renewed when necessary.
[Illustration: _Fig. 254._]
Take a rod of soft steel of a diameter half as large again as that
of the square to be made. Drill a hole along its axis rather less in
diameter than the set-hands arbor and cut off the ends a little longer
than the square is required to be. Put this nut on an arbor and turn it
flat on each end (although still a little long) and truly cylindrical.
Having inserted a loose fitting coned brass wire of oval section into
the nut, hold it on its side on an anvil. With a sharp blow of the
hammer cause the cylinder to assume an oval form, so that the round
hole is as seen at A, Fig. 254, this being the section of the end of
the set-hands arbor itself. If the work has been carefully performed up
to this point, the steel nut should now pass a short distance on to the
arbor on applying a moderate pressure, and it will suffice to slightly
alter the form of this latter in order to ensure a perfect fit. As
there should be no shake, it is advisable that this adjustment be made
after the nut is hardened.
File the two faces _d_ and _f_ parallel to each other and to the axis
of the oval, reducing the total thickness very nearly to the amount
ultimately required, then holding the nut in the pincers by these two
faces firmly, but without scratching them (or it may be held by a rod
fitted to the oval hole), form the square, removing all the metal that
is beyond the two vertical lines in the figure. Then set it on an oval
arbor and turn the corners down to the exact diameter required; pass
the graver over the two ends so as to adjust the length. It will then
be easy to finish off the square and round the lower end, holding
the nut on a steel rod in a pin-vise. Drill the hole for a pin after
marking its two ends on the nut as explained in article =518=, then,
holding the nut so that it rests on its lower face, form a recess with
a chamfering tool held in its axis; the form of this can be modified if
required with the rounded end of a rod and oilstone dust.
Harden the square and temper it to a blue color; then smooth its faces
and ends, and fit the square to the set-hands arbor. The hole for the
pin must now be made through this arbor, taking care not to allow the
square to rise out of its place during the operation. It only remains
to polish the recess formed in the nut with a rod rounded at one end
and rotated with a ferrule, and finish off the corners with a burnisher
and rouge; the lower end is finished in the same manner as the head of
a screw.
=553.= We have here considered the case of a new arbor, but, if fitting
a nut to one that is already drilled, proceed as follows: Make the nut
rather longer than necessary and drill a hole higher than the point
at which measurement shows it ought to be; then remove metal from the
lower face until the two holes coincide. The work is simplified if the
nut be made of the correct height at once and, instead of drilling a
hole, a slit be formed as in the head of a screw, the bottom of which
must correspond with the lower edge of the hole in the arbor.
=554.= =To fit the Set-hands Arbor to the Center or cannon pinion.=
We have pointed out in article =364=, the objections to hammering the
set-hands arbor so as to secure sufficient friction to make it hold
in either of the pinions through which it passes in the ordinary form
of watch. Tracing a spiral line on its surface is not much better, as
the metal thus caused to project soon wears off. A better method is
explained in article =337=, but, when only a slight increase of diameter
is needed, the following will suffice:
Roll the arbor on a hard flat wood surface with a file of medium cut,
applying considerable pressure so that the arbor is forced against the
file. If the pressure is sufficient and maintained long enough, a dead
rough surface will be formed on it which will increase its diameter so
that it will retain a small quantity of oil. It is well to roughen the
surface rather more than necessary, subsequently passing a burnisher
lightly over it until the arbor fits the pinion with sufficient
friction.
As to the making of a set-hands arbor, it will present no difficulty to
a watchmaker of even average skill in turning and filing.
PIVOTS.
=555.= =The Play Of Pivots.= It may be accepted as an approximate rule
that the play of escapement pivots in their holes should be as follows:
In the cylinder escapement, about one-sixth the diameter of pivot.
In the duplex escapement, about one-tenth the diameter of pivot.
In the lever escapement, about one-eighth the diameter of pivot.
A large hole causes the pitching of the depths to vary with position,
and a deficient play renders the escapement more sensitive to
thickening of the oil.
The depth of a pivot-hole or the length of its cylindrical acting
surface may be taken to vary inversely with its hardness. Thus a ruby
hole is made less deep than one of brass.
=556.= =To Replace the Pivot of a Hollow Pinion.= It often happens that
the pivot of a hollow center pinion is so deeply cut that it cannot
be re-polished, in consequence of the careless manner in which too
many examiners finish the center holes (=461=). If the pinion itself
is found to be still in good condition, it can be made serviceable as
follows:
Cement the pinion, with its wheel attached, firmly to the chuck of
a lathe after having removed the two worn pivots, and, when it is
accurately centered, increase the hole by means of a drill that is a
trifle larger than the original pivots (see article =282=); in the hole
thus enlarged and carefully smoothed insert a close fitting steel tube
that has been hardened and tempered to a blue color, which must be
smoothed and run true. The portion of this tube that projects on either
side is then adjusted to the proper length, and it only remains to
polish the pivots.
If only one pivot requires renewal, ascertain whether there would be
sufficient hold with the hole enlarged through half its length, and
proceed as already explained.
We have assumed that the shoulders of the original pivots can be made
to serve again, but it often happens that the shoulders do not possess
sufficient substance, in consequence of the hollows being cut too
deep. In such a case it is hardly necessary to observe that the hole
must be drilled larger, so that, after the tube has been adjusted, new
shoulders can be turned on it.
=557.= =To Redress a Bent Pivot.= For this purpose some workmen merely
use a pair of pliers or tweezers; others place the pivot in a slot of
the Jacot tool, and press on it with a burnisher that has little or no
cut, at the same time causing the staff to rotate. Either of the two
following methods may be adopted:
Drill a number of straight holes in a plate exactly at right angles to
its surface. Now introduce the pivot into a hole that it fits with very
little play, and redress it by causing the staff to rotate, at the same
time holding the plate in the hand. Caution is necessary since there is
some risk of bending the pivot too far.
=558.= =Pivoting a Cylinder, etc.= This operation will not present
any difficulty if the several heights are properly taken. See also
the articles on Beaupuy files (=240=), and on compasses for measuring
heights, etc. (=243=).
=559.= =Polishing Pivots in the Lathe.= Pivots are as a rule polished
by metal polishers provided with suitable materials, and held in
the hand; in Fig. 255, however, is given the design of a machine by
which this work can be accomplished when the pivoting is done in the
chuck-lathe, the pivot itself being free and unsupported by a runner.
[Illustration: _Fig. 255._]
The bed P of the instrument carries a wheel R which engages with a
pinion on the axis of the polishing lap _m_. The wheel R is mounted on
a clock stud passing through a slot and fixed by a nut, so that the
pitching of the two mobiles may be modified; motion is communicated
to the lap by simply placing the finger against the teeth of R. The
bed can move in a vertical plane, being pivoted on two screws, _v_,
_v_, and the block that receives the points of these is riveted to the
disc _d d_, which can be made to rotate, with friction, on the second
disc _n n_. This latter is riveted to a plate _e_ fixed at the end of a
cylindrical rod F.
It will be evident that if the rod F is inserted in the =T=-rest
support, the plate P extending towards the back of the lathe, this
plate can be raised or lowered, and moved towards the right and left,
so that the flat face of the lap can always be brought in contact with
the pivot that is to be polished. This latter is caused to rotate by a
foot-wheel while one hand holds the raised plate by the button _a_, and
a finger of the other hand is applied to the teeth of R, causing the
lap to rotate.
The upward motion of P may be limited by the edge of the top _s_ of the
button _s k_, which is tapped so as to rotate with stiff friction on
the pillar H. The stop _l_ is to prevent the polisher from traveling
too far towards the left and thus removing too much from the shoulder
that is to be polished. The screw _x_, giving motion to the slide _y_,
is for securing parallelism between the pivot and the surface of the
lap, according as the former is cylindrical or conical in shape.
For fine pivots it is advisable to introduce an additional wheel and
pinion. The finger will then be better able to appreciate the degree of
resistance opposed, and, owing to the increased velocity, it will be
useless to use oilstone dust, but rouge can be applied directly after
the turning. At _e_ is a steady-pin for maintaining the position of the
instrument.
BUSHING PIVOT HOLES, ETC.
=560.= Every watchmaker knows how to proceed in adjusting an ordinary
perforated bushing or stopping. We would make a few remarks on the
subject of bushings generally.
The tapped bushing is very firm, but, in order that it may be well
centered, it is essential that its thread fits exactly the tube of the
tool (=322=), and that the pointed rod is exactly central. A turned
bushing, especially when a broach can be passed into it after it is in
position, is more easily made central (see article =342=).
When bushing holes that are rather large with solid bushings, after
the hole has been marked with the pointer it must be drilled with a
small drill, a larger one being subsequently passed through, so as to
increase it. Otherwise there is great danger of the hole turning to one
side.
If a hole, such as that of the center wheel, is bushed with a
perforated bushing, it will often be found to incline towards the
barrel or fusee, so that the hole is displaced. Such an inconvenience
may be avoided by using a bushing with a hole smaller than is
ultimately required, afterwards enlarging it with the plate centered in
the lathe.
=561.= =Riveting of Bushings.= Some watchmakers have found considerable
advantage in replacing the sudden and irregular impacts of a hammer
by gradual pressure, without shock, obtained by a small press worked
by hand on the principle of a punching machine. With a well made
bushing, the flat end of which is slightly rounded, and the inside
of the hole in the plate finished with a rat-tail rather than with a
cross file, it is found that the riveting is always perfect. Others
employ an ordinary pair of sliding tongs, the noses of which are
drilled to receive two punches, one flat and the other rounded, as in
the mainspring punch. Three pairs of punches suffice for all sizes of
bushings, and the same tool can be used for closing up screw-holes, etc.
[Illustration: _Fig. 256._]
=562.= =Movable Bushings.= These are for use in regulator clocks
and others of large dimensions, and a few words must suffice for
their description. They are the invention of M. Alleaume, and will
be understood from Fig. 256. It is always desirable, with a view to
prevent wear, that when metal pivot-holes are used, the pivot should
bear on a length equal to about three times its diameter; but for such
a condition to be satisfied, it is essential that the axes of both
holes and pivots be absolutely parallel. The figures will at once
show in what manner such parallelism is secured. C C is the plate, in
section, in which a hole is made of the form indicated by the lines
that bound the cross-hatchings. The movable bushing A is held against
a shoulder, and prevented from rotating by a screw, the point of which
enters a small hole in the bushing. The pivot of B passes into A, and
this latter is capable of such slight motion as will insure contact
between the surfaces throughout their length.
DEPTHS.
=563.= =To Secure a Good Depth.= The least skillful of watchmakers
can, without much difficulty, place a wheel in the depthing tool in
conjunction with a pinion, and change this latter until the two are
found to run easily together. But there are comparatively few that are
sufficiently acquainted with the subject of depths to be able to select
a pinion whose proportions are such as to satisfy the greatest number
of the conditions to be fulfilled by a good depth.
This unsatisfactory state of things is due in great measure to the
employment, without any correction, of tables of the sizes of pinions
(=544=), according to which these sizes are determined by a measurement
on the teeth of the wheel, taken with a pinion caliper. This method,
although sufficient for ascertaining the size approximately, and even
for securing a depth that runs more or less easily, cannot be accepted
as an unvarying rule.
Far from resting on any mathematical law, as ignorant men urge in their
attempt to instruct others, it is only true for a particular number and
form of tooth in regard to the wheel, and a definite thickness of leaf
and shape of the rounding in regard to the pinion. It ceases to be true
if applied to other numbers of teeth, or to pinions that have their
leaves thicker or thinner, or the roundings different from those of the
pinion first determined upon.
=564.= _Theoretical and practical depths._ The fundamental principle
of every depth is as follows: To determine what curvature should be
given to the teeth of the wheel which drives, in order that the tooth
that follows (whether its side be straight or formed according to a
pre-determined curve) shall be driven in such a manner as to secure the
best transmission of force, a transmission which is in part influenced
by the uses to be made of the machine.
=565.= Teeth formed like the involute of a circle have very marked
advantages, but they cannot be adopted in practice, especially in the
case of the leaves of pinions. The epicycloid can be realized very
approximately in the teeth of wheels in horology, and such teeth can
be used in conjunction with pinion leaves having straight faces, the
construction of which does not present any difficulty. This explains
why the epicycloidal form has been adopted by watchmakers; but,
although it is more easily drawn than the majority of other curves,
there are still some obstacles in the way of its general application,
mainly dependent on industrial requirements. The difficulty is usually
got over by forming the tooth according to a circular arc, nearly
identical with the epicycloidal curve, see articles (=440-42=).
=566.= When two mobiles are of the _same diameter_, the theoretical
depth will be characterized by having teeth and spaces of equal width;
but, since in practice the friction with such an arrangement would be
excessive, owing to its taking place on both sides of the tooth, the
teeth of the wheel that are driven are so far reduced in thickness as
to secure the necessary freedom.
=567.= When the two mobiles are very highly numbered, the lead is
short, so that the tooth of the wheel may be a trifle broader or
narrower than the space without inconvenience.
But when using pinions of low number (from 6 to 10 leaves), this is not
the case. In proportion as the width of the wheel tooth is reduced,
its ogive becomes shorter, and the most advantageous portion of the
lead (that beyond the line of centers) becomes less. And, besides this,
account must be taken of the slipping towards the end of the lead, and
the reduction in the difference between the geometrical and the total
diameters of the wheel.
=568.= To secure a good depth with low numbered pinions, the leaves
should not be more than half the thickness of the space. If they are
thicker than this, it may be found necessary to reduce the width of
the wheel teeth, when the pitching is insufficient; but the most
serious objection lies in the fact that the pitch circle of the
pinion will be diminished in diameter. Let there be two pinions with
circular roundings and of the same total diameter, but having leaves of
different thicknesses—that with the leaves thick will be found to be
too small, etc.
=569.= =To Calculate the Vibrations of a Pendulum or Balance.= Multiply
together the numbers of teeth of the wheels, starting with the one that
carries the minute hand (which therefore makes one revolution in an
hour), but exclude the escape-wheel.
Multiply together the numbers of leaves of the pinions, commencing with
the one that engages with the center-wheel.
If the first product be divided by the second, the number obtained
gives the _number of revolutions_ of the escape-wheel in an hour.
Multiply this figure by _twice the number_ of teeth of the
escape-wheel, and the product is the _number of single vibrations
performed by the balance or pendulum in one hour_.
ON THE APPLICATION OF THE GEOMETRICAL LAWS OF DEPTHS TO PRACTICE.
=570.= It has been urged that when the geometrical forms of the leaves
and teeth, as given in scientific treatise, are accurately carried
out in practice, the depths are found to be unsatisfactory and liable
to cause occasional stoppage; and these facts are brought forward as
evidence that theory and practice are at variance.
On the contrary, theory and practice are in perfect accord: the
apparent disagreement arises from an error in the application of the
geometrical laws.
In copying the theoretical forms of the teeth of wheels and leaves
of pinions, it would be necessary to ascertain that they were
mathematically exact, and this is impracticable. Two conditions must be
borne in mind:
1. Theory shows that the mobile which drives should be made a trifle
larger than the geometrical size, so as to counteract imperfections in
the workmanship.
2. A pinion is _never_ made of the exact mathematical proportions,
in consequence of the processes that have to be adopted for cutting,
polishing, centering, etc. If a number of pinions be taken, and
if the several dimensions of each be determined by means of a
micrometer measuring to hundredths of a millimeter (or from two to
three-thousandths of an inch), differences that are, comparatively
speaking, large will be found in the diameters, measuring between
corresponding leaves; in the thickness of leaves; in the diameters
of the circles at which the roundings join the straight faces, and
the general truth of the pinion will nearly always leave something to
be desired. It should be added that these faults will be more marked
according as the leaves have been more quickly made.
The teeth of wheels will be found to be characterized by similar
faults, although they are less marked.
=571.= It follows from these facts that, in watches and timepieces, the
_pinion is always a little smaller_ than theory would require; thus the
epicycloid should be struck with a somewhat smaller generating circle,
and the ogive of the tooth will be proportionately reduced.
The _practical conclusion_ at which we arrive, then, is as follows: As
it is impossible to secure absolute perfection in the teeth of small
horological mechanisms, their ogives must be slightly more rounded at
the points than the designs given in scientific treatises indicate,
since these latter are drawn exactly in accordance with the geometrical
laws.
These remarks are of the greatest possible importance to the
manufacturers of both watches and timepieces; they point to the fact
that not only the ogives of all wheel teeth should be lower than theory
indicates, but also that, in commoner work, they must be still lower,
according as the pinions are of more inferior quality.
=572.= =To Alter a Stem Winding Pinion Depth.= The depth of the Stem
Winding Wheel and Pinion often occasions considerable inconvenience,
and its adjustment requires to be accurately made: when the depth is
too deep, its alteration is easy, as the roundings of the pinion leaves
can be reduced, or the stud or other piece that carries the winding
wheel can have its base a little reduced on one side, so as to set the
wheel a trifle out of upright (but so slightly as not to be perceptible
to the eye, and taking care that the teeth remain on a level with those
of the barrel-arbor wheel). A shallow depth is somewhat more difficult
to correct. If a sufficient change cannot be made by altering the
support of the winding wheel, one of the following methods must be
resorted to:
1. Reset the pendant of the case.
2. Make a new winding pinion of greater diameter, increasing the number
of its leaves by one, to correspond to this change.
3. Alter the position of the movement in the case.
The two first methods are more especially applicable to new work, while
the third is more convenient for repairers, although of course it can
only be resorted to with advantage when the pinion has a bearing in
the pendant. The requisite change in the position of the movement can
be produced by raising the rim of the case that supports the plate, or
by soldering two thin strips of metal on this rim, producing a similar
effect; one on either side of the pendant will suffice, except when a
considerable change is necessary, in which case they should be set at
intervals around the rim to avoid an obvious inclination of the dial.
Or four holes can be drilled at equal distances apart around the edge
of the plate and in its plane, so that their edges overlap the position
occupied by the rim of the case; pins are then set in these holes and
filed away until they produce the requisite amount of elevation. Or,
again, flat-headed screws may be fitted around the edge with their axes
at right angles to the plane of the plate and their heads on the dial
side.[7] The depth will then be adjusted by screwing these screws more
or less into the plate.
It is advisable to ascertain that the dial is not forced too near the
glass, as such is occasionally found to be the case, necessitating the
bevelling of the edge of the former.
PALLETS.
=573.= =To Advance a (visible) Jewel in a Pallet.= Workmen that
have had much experience of escapement making do this without any
difficulty by holding the pallet arm in a pair of tweezers that have
been slightly warmed, but ordinary repairers will not succeed with such
a method: they can however, effect the required change as follows.
[Illustration: _Fig. 257._]
Make a small brass plate, E, fig. 257, with a piece _c_ projecting
upwards, which the screw _v_ traverses with stiff friction. A saddle
_b_ is fitted to the edge of the plate by screws. A glance at the
figure will suffice to show the mode of using it; the pallet arm whose
jewel is to be adjusted is clamped under _b_ with the jewel just
opposite the screw _v_. Now turn this screw until it stands at the
distance from the impulse face of _a_ through which the jewel is to be
advanced; taking the plate in a pair of long-nosed pliers, hold them
over a small lamp flame, and press with a small screwdriver lightly
against the point _a_ so as to advance the stone by the requisite
amount as soon as the shellac is sufficiently soft. A particle of
shellac is placed at _a_, if any cavity forms during the process,
and the plate is laid on some cool body, avoiding contact with the
pallet-staff.
If the stone projects below the lower surface of the pallets, a small
washer must be placed underneath before clamping the screws of _b_, of
such a thickness that the stone is just on the level with the surface E.
=574.= =To Alter the Form of a Pallet Face.= Workmen that possess the
requisite skill and steadiness of hand can alter the form of a pallet
jewel, when it is necessary to modify the height or form of the impulse
face, by simply using a copper polisher charged with diamond powder.
The polishing material employed is always decanted in very pure oil, as
otherwise it is apt to scratch instead of polish. The coarser quality
is first used when a material change has to be effected, but if only a
very slight alteration is necessary, and the adjustment has to be very
exact, only the finest quality must be used, as there is a danger of
making scratches that would be very difficult to erase. We would also
add that this operation requires some skill and patience.
[Illustration: _Fig. 258._]
=575.= =To Measure the Lift and all other Angles, etc. of the Lever
Escapement.= A very simple instrument for measuring these angles was
designed by Curzon, one which any watchmaker can arrange for himself,
and is quite sufficient for all practical purposes. This is shown in
Fig. 258, and consists of an ordinary depth tool to which a scale is
added. A hand adapted to the pallet-staff supported between one pair
of runners of the depth tool gives motion to a curved rack (shown by
dotted lines), and this causes a pinion carrying a second index to
rotate, the radii being so related that the movement of the staff is
magnified four times on a scale which can be observed while the glass
is at the eye examining the pallets. The index which travels over the
shorter scale to the left (divided up to 10° on either side of zero)
is connected with the pallet-staff by a fork and a short arm passing
through the circular groove; it affords a convenient means of moving
the pallets while testing them, and gives a measure, in degrees, of
their motion. The graduated arc shown at the top is for measuring the
lever and roller.