THE CONSTRUCTION AND REPAIR OF DIALS.
Probably no portion of the clock is more important than the dial and
it is apparently for this reason that we find so little variation
in the marking. The public refuses to accept anything in the way of
ornamentation which interferes with legibility and about all that may
be attempted is a little flat ornament in light colors which will not
obscure the sight of the hands, as it is in reality the angle made by
the two hands which is read instead of the figures. In proof of this
may be cited the many advertising dials in which one letter takes
the place of each character upon the dial and of the tower clocks in
which the hours are indicated merely by blackened characters, being
nothing less than an oblong blotch on the dial. Thousands of people
will pass such a dial without ever noticing that the regular characters
do not appear. Various attempts have been made to change the colors
and the sizes and shapes of the characters but comparatively few are
successful. A black dial with gold characters and hands is generally
accepted, or a cream dial with black hands, but any further experiments
are dangerous except in the cases of tower clocks, which may have
gold hands on any light colored dial, or a glass dial. In all such
cases legibility is the main factor sought and the bright metal is far
plainer for hands and chapters than anything that may be substituted
for them.
In tower clocks the rule is to have one foot of diameter of the dial
for every ten feet of height. Thus a clock situated one hundred feet
above the ground level should have a ten foot dial. On very large dials
this rule is deviated from a little, but not much. All dials, except
those of tower clocks, should be fastened to the movement, rather than
to the case. This is particularly true where a seconds hand, with
the small opening for the seconds hand sleeve, makes any twisting or
warping of the case and consequent shifting of the dial liable to rub
the dial against the sleeve at the seconds hand and thus interfere with
the timekeeping.
The writer has in mind a case in which a large number of fine clocks
were installed in a new brick and stone building. They were finely
finished and no sooner had they been hung on the damp walls than the
cases commenced to swell and twist. It was necessary three times
to send a man to move the dials which had been attached to these
clocks. As there were about thirty clocks it will be seen that this
was expensive. After the walls had dried out the cases began to go
back to the positions in which they were originally, as the moisture
evaporated from the cases, and the dials had consequently to be moved
through another series. All told it took something like a week’s work
for one man to shift these dials half a dozen times during the first
nine months of their installation. If these dials had been fastened on
pillars on the movements, the shrinking and swelling of the cases would
not have affected them.
It is for this reason that dials are invariably fastened on the
movements of all high class clocks.
The characters on clock dials are still very largely Roman, the
numerals being known as chapters. Attempts have been recently made to
substitute Arabic figures and in such cases the Arabic figures remain
upright throughout the series, while the chapters invariably point the
foot of the Roman numeral toward the center of the dial. This makes
the Roman numerals from IIII to VIII upside down, while in the Arabic
numerals this inversion does not occur.
The proportions generally sanctioned by usage have been found, after
measuring clock dials, all the way from two to eighteen inches, and
may be given in the following terms: With a radius of 26 mm. the
minute circle is 1½ mm. The margin between minute circles and chapters
is 1 mm. The chapters are 8½ mm. The width of the thick stems of the
letters are ¾ mm. The width of an X is 4 mm. and the slanting of X’s
and V’s is twenty degrees from a radius of the dial. The letters should
be proportioned as follows: The breadth of an I and a space should
equal one-half the breadth of an X, that is, if the X is one-half inch
broad, the I will be three-sixteenths inch broad and the space between
letters one-sixteenth inch, thus making the I plus one space equal
to one-quarter inch or half the breadth of an X. The V’s should be
the same breadth as the X’s. After the letters have been laid off in
pencil, outline them with a ruling pen and fill in with a small camel’s
hair brush, using gloss black paint thinned to the proper consistency
to work well in the ruling pen. Using the ruling pen to outline the
letters gives sharp straight edges, which would be impossible with a
brush in the hands of an inexperienced person.
For tower clocks the chapters and minutes together will take up
one-third of the radius of the dial; the figures two-thirds of this, or
two-ninths of the radius, and the minutes two-thirds of the remaining
one-ninth of the radius, with every fifth minute more strongly marked
than the rest.
We often hear stories concerning the IIII in place of IV. The story
usually told is that Louis XIV of France was inspecting a clock made
for him by a celebrated watchmaker of that day and remarked that the IV
was an error. It should be IIII. There was no disputing the King and so
the watchmaker took away the dial and had the IIII engraved in place of
IV, and that it has thus remained in defiance of all tradition.
Mr. A. L. Gordon, of the Seth Thomas Clock Co., has the following
to say concerning this story and thus furnishes the only plausible
explanation we have ever seen for the continuance of this manifest
error in the Roman numeral of the dial:
“That the attempt has been made to use the IV for the fourth hour on
clock dials, any one making a study of them may observe. The dials on
the Big Ben clock in the tower of the Parliament buildings, London,
which may be said to be the most celebrated clock in the world, have
the IV mark, and the dial on the Herald building in New York City also
has it.
“That the IIII mark has come to stay all must admit, and if so there
must be a good and sufficient reason. Art writers tell us that pictures
must have a balance in the placing and prominence of the several
subjects. Most conventional forms are equally balanced about a center
line or a central point. Of the latter class the well known trefoil is
a common example.
“A clock or watch dial with Roman numerals has three points where the
numerals are heavier, at the IIII, VIII and XII. Fortunately these
heavier numerals come at points equally spaced about the center of
the dial and about a center line perpendicular to the dial. Of these
three heavy numerals the lighter of them comes at the top and it is
especially necessary that the other two, which are placed at opposite
points in relation to the center line, should be balanced as nearly
as possible. As the VIII is the heavier and cannot be changed, the
balancing figure must be made to correspond as nearly as possible, and
if marked as IV, it will not do so nearly as effectively as if the
usual IIII is used.”
It is comparatively an easy matter to make a metal dial either of
zinc, copper or brass, by laying out the dial as indicated above with
Roman chapters and numerals, after first varnishing the metal with
asphaltum. This may be drawn upon with needle points which cut through
the asphaltum and make a firmly defined line on the metal. It is best
to lay out your dial in lead pencil and then take a metal straight edge
and a needle point and trace through on the pencil marks. Mistakes may
be painted out with asphaltum, so that the job becomes easy. After
this has been done a comparatively dull graver may be used to cut or
scrape away the asphaltum where the metal is to be etched and then the
plate may be laid in a tray, a solution of chloride of iron poured on
and rocking the tray will rapidly eat away the metal, forming sunken
lines wherever the copper or brass is not protected by the asphaltum.
This furnishes a rough surface on the etched portions, which enables
the filling to stick much better than if it were smooth. In tracing the
circles a pair of heavy, stiff, carpenters’ compasses will serve where
the watchmaker has not a lathe large enough to swing the dial. In all
such cases it is best to start with a prick-punched center, tracing the
minute circles and the serifs of the chapters with the compasses and
then do your further division and marking by lead pencil, followed with
the needle and then by the acids. It should be done before the holes
are bored for the minute and seconds centers, as you then have an exact
center to mark from and can go back to it many times.
This will be necessary in dividing the minute or seconds circle by hand
(without an index on the lathe), as one of the tests of true division
consists in having all marks lined up with a straight edge placed
across the center. Thus IX and III should be in line with the center;
VI and XII; X and IIII; I and VII, etc. It will readily be seen that
for such purposes of reference the center should not be punched too
large.
If it is desirable to ornament the dial, the desired ornament may be
drawn on in the plain surface through the asphaltum and etched at the
same time as the chapters and degrees. Or chapters and ornament may
be drawn, pierced with a saw, engraved, filed up and backed up with a
plain plate of another color. Gold ornament and silver background looks
well.
Practically all the clocks having seconds hands carry that hand in
such a position as to partially obscure the XII, with the exception
of watchmakers’ regulators, and these, if they have separate hour,
minute and seconds circles, are made large enough to occupy the space
between the center and the minute circle, placing the hour circle
between the center and the thirtieth minute; the seconds between the
center and the sixtieth minute. The reason for this is that in the
watchmakers’ regulators the hours are almost a matter of indifference;
minutes are seldom referred to; the real comparison in watch regulation
comes on the seconds hand. For this reason the seconds hand is made as
large as possible and the chapters being placed on the hour circle by
themselves, the seconds circle may occupy almost the entire distance
between the center of the dial and the minute circle. They are placed
one above the other because in regulators the time train is nearly
always a straight-line train, which brings the seconds arbor vertically
over the center arbor, and consequently the centers of the dials must
be placed on a vertical line.
When the engraving has been properly done on a flat dial it is
desirable to fill it with black in order to make it legible. There are
several methods by which this may be done. The most durable is to make
a black enamel and if it is a valuable clock the movement is generally
worth a fine dial. The following formula will furnish a good black
enamel:
Siliceous sand 12 parts
Calcined borax 20 parts
Glass of antimony 4 parts
Saltpetre 1 part
Chalk 2 parts
Peroxide of Manganese 5½ parts
Fine Saxony Cobalt 2 parts
The enamel is ground into coarse particles like sand, and the incised
lines filled with it, after which the brass or copper plate is heated
red hot to fuse the enamel. Two or three firings may be necessary to
completely fill the lines; after filling they are stoned off level with
the surface of the dial. Jeweler’s enamel may be purchased of material
dealers and used for the dials.
Black asphaltum mixed with a little wax or pitch, or even watchmakers’
cement, used to fasten staffs and pinions into a lathe for turning, is
also used on these dials and with a sufficient proportion of wax or
pitch it prevents shrinking and forms a very satisfactory dial with the
single exception that it cannot be cleaned with benzine or hot potash,
which will dissolve the enamel. Shoemakers’ heel ball is also used
for repair jobs. In order to make either of these stick, the brass or
copper plate is heated up so as to “hiss” as will a laundry flat iron
when touched with a wetted finger, and a cement stick is rubbed over
the letters to fill them; the excess of filling can be scraped off
with an ivory scraper when at the right temperature—a little below the
boiling point of water. Such filled letters can be lacquered over by
going very quickly over the work so as not to dissolve the shellac in
the cement.
Another way is to fill the letters with black lacquer. For quick
repairs this is probably as good as any. Many of the old grandfather
clocks have been filled in with a putty made with copal varnish and
some black pigment. All putties shrink in drying and consequently
crack and finally fall out. The wax and pitch are not subject to these
disadvantages. If the plates are to be polished, polishing should
precede the filling in of the letters, else the work may have to be
done all over again. Black sealing wax and alcohol are also used,
applied as a paint with a fine brush.
If the dial is to be silvered or gilt the blacking should be done
first, and if to be electroplated the blacking should be what is known
as the “platers’ resist,” which is composed chiefly of asphaltum and
pitch dissolved in turpentine. It is also called “stopping-off”
varnish, and has large use in the plating establishments to prevent
deposition of metal where it is not desired.
The repairer who gets many grandfather clocks will often find that it
is necessary to repaint the dial, generally because of a too vigorous
scrubbing, or because of cracks or scaling, which the owner may
dislike. It is always best, however, to be cautious in such matters,
as many people value such a clock chiefly on account of its visible
evidences of age and such cracks form generally a large proportion of
such evidence. Therefore it is best never to touch an antique dial
unless the owner desires it.
Such dials are usually sheet-iron, and tolerably smooth, so the metal
will need but a few coats of paint to prepare it. For ground coats,
take good, ordinary white-lead or zinc white, ground with oil, and if
it has much oil mixed with it pour it off and add spirits of turpentine
and Japan dryer—a teaspoonful of dryer for every half pint of paint.
The test for the paint having the right amount of oil left in it is,
it should dry without any gloss. Rub every coat you apply with fine
sand paper, after it is perfectly dry, before applying the next coat
of paint. For the final coat, lay the dial flat and go over it with
French zinc white. This coat dries very slow, and for a person not
used to such work, is hard to manage. The next best (and for ordinary
clock or watch making _the best_) for the last pure white coat is to
take a double tube of Windsor & Newton’s Kremnitz white, thinned with a
little turpentine. Such tubes as artists use are the kind. Apply this
last white coat with a flat, camel’s hair brush. The tube-white should
have turpentine enough added to cause it to flow freely, and sink flat
and smooth after the brush. The letters or figures should be painted
with ivory-black, which is also a tube color. This black is mixed with
a little Japan, rubbing varnish and turpentine, and the lettering is
done with a small, sign writer’s pencil. Any flowers or ornaments are
painted on at the same time; and after they are dry the dial should be
varnished with Mastic or Damar varnish or white shellac. All kinds of
coach (Copal) varnish are too yellow.
Painted dials on zinc will blister and crack off if subjected to
extremes of heat and cold, unless they are painted with zinc white
instead of lead for all white coats. The reason is the great difference
in expansion between lead paint and metallic zinc. This case is similar
to that of using an iron oxide to paint iron work of bridges, ships,
etc., where other oxides will chip and scale off.
The metal dials on these old clocks were silvered by hand. When you get
such a dial, discolored and tarnished, it can be cleaned in cyanide and
resilvered, without sending it to an electroplater, by the following
formula:
Dissolve a stick of nitrate of silver in half a pint of rain water;
add two or three tablespoonfuls of common salt, which will at once
precipitate the silver in the form of a thick, white curd, called
chloride of silver. Let the chloride settle until the liquid is clear;
pour off the water, taking care not to lose any chloride; add more
water, thoroughly stir and again pour off, repeating till no trace of
salt or acid can be perceived by the taste. After draining off the
water add to the chloride about two heaped tablespoonfuls each of salt
and cream of tartar, and mix thoroughly into a paste, which, when
not in use, must not be exposed to the light. To silver a surface of
engraved brass, wash the surface clean with a stiff brush and soap.
Heat it enough to melt black sealing wax, which rub on with a stick of
wax until the engraving is entirely filled, care being taken not to
burn the wax. With a piece of flat pumice-stone, and some pulverized
pumice-stone and plenty of water, grind off the wax until the brass is
exposed in every part, the stoning being constantly in one direction.
Finish by laying an even and straight grain across the brass with blue
or water of Ayr stone. Take a small quantity of pulverized pumice-stone
on the hand, and slightly rub in the same direction, which tends to
make an even grain; the hands must be entirely free from soap or
grease. Rinse the brass thoroughly, and before it dries, lay it on a
clean board, and gently rub the surface with fine salt, using a small
wad of clean muslin. When the surface is thoroughly covered with salt,
put upon the wad of cloth, done up with a smooth surface, a sufficient
quantity of the paste, say to a dial three inches in diameter a piece
of the size of a marble, which rub evenly and quickly over the entire
surface. The brass will assume a greyish, streaked appearance; add
quickly to the cloth cream of tartar moistened with water into a thin
paste; continue rubbing until all is evenly whitened. Rinse quickly
under a copious stream of water; and in order to dry it rapidly, dip
into water as hot as can be borne by the hands, and when heated,
holding the brass by the edges, shake off as much of the water as
possible, and remove any remaining drops with clean, dry cloth. The
brass should then be heated gently over an alcohol lamp, until the wax
glistens without melting, when it may be covered with a thin coat of
spirit varnish, laid on with a broad camel’s hair brush. The varnish or
lacquer must be quite light colored—diluted to a pale straw color.
It is now possible to buy silver plating solutions which can be used
without battery and they will produce the same effect as the formula
just given. If they happen to be in stock for the repairing of jewelry
they may be used in cleaning the dials, but as this is liable to fall
into the hands of many who are far from such conveniences, we furnish
the original recipe, which can be executed anywhere the materials can
be obtained.
If the dial is of brass, very good effects have been produced by
stopping off portions of the dial in an ornamental pattern before
silvering, and then lacquering after removing the resist. But for a
plain black and brass dial a dip of strong sulphuric acid two parts,
red fuming nitrous acid one part, and water one part, mixed in the open
air and dipped or flowed over the dial, forms what is known as the
platers’ bright dip. After dipping the article should at once be rinsed
in hot water and dried, and lacquered at once with a lacquer of light
gold color. This makes a very neat and durable finish.
The satin effect may be obtained on a dial by prolonging the acid dip
and otherwise proceeding as before. Many of these dials were of zinc
and all that applies to brass or copper may be also executed in zinc,
but in plating it will be found necessary to plate two or three times,
as the single coating will apparently disappear into the zinc unless
it is given a heavy deposit of copper in a plating bath. Where it is
desired to obtain a bright gold color, the gold plating solutions
now sold for the coloring of jewelry may also be used on either of
these metals. For the reasons given above, however, they are not very
successful on a zinc base.
Many of the cheap clocks have paper dials glued on a zinc plate and
when the dial is soiled the repairer cleans them up by pasting another
dial on top of the original. These dials are made on what is known as
lithographic label paper; that is paper which is waterproof on one
side, so that it will not shrink or swell when dampened. In addition to
the lithograph coating they are generally given a varnish of celluloid
by the clock manufacturers, thus making them practically waterproof.
They are very cheap and the repairer will find that he will obtain in
prestige from such new dials far more than they cost.
Tarnished metal dials are best cleaned by a dip of cyanide of
potassium, of about the same strength as that used for cleaning silver.
If the tarnished parts have been gilded, however, the cyanide should be
excessively weak. Mining men use a cyanide solution for the recovery
of gold, which is only two-tenths of one per cent cyanide, and this
will collect all the gold from ore that runs from $10 to $15 to the
ton, the pulp in such cases being left in the solution from seventy to
ninety hours. The ordinary cyanide dip for the jeweler is one ounce
to thirty-two of water, while the miner’s solution is two-tenths of an
ounce to one hundred ounces of water. You can see that with the strong
cyanide solution the gilt surface will all be taken off unless very
rapid dipping is strictly followed by thorough washing.
A novelty which keeps periodically coming to the front, say about once
every ten years, is the luminous dial. This is done by painting the
dial with phosphorus or a phosphorescent powder. Then when it is placed
in the light it will absorb light and give it off in the dark until the
evaporation of the phosphorus.
The composition and manufacture of this phosphorescent powder is
effected in the following manner: Take 100 parts by weight of carbonate
of lime and phosphate of lime, produced by calcination of sea-shells,
especially those of the tridacna and cuttlefish bone, and 100 parts
by weight of lime, rendered chemically pure by calcination. These
ingredients are well mixed together, after which 25 parts of calcinated
sea salt are added thereto, sulphur being afterward incorporated
therewith to the extent of from 25 to 50 per cent of the entire mass,
and a coloring matter is applied to the composition, which coloring
matter consists of from 3 to 7 per cent of the entire mass of a powder
composed of a mono-sulphide of calcium, barium, strontium, magnesium
or other substance which has the property of becoming luminous in the
dark, after having been impregnated with light. After these ingredients
are well mixed, the composition is ready for use. Its application to
clock dials is made either by incorporating suitable varnish therewith,
such as copal, and applying the mixture with a brush to the surface
of the dial, or by the production of a dial which has a self-luminous
property, imparted to it during its manufacture. This is effected in
the following manner: From 5 to 20 per cent of the composition obtained
and formed as above described, is incorporated with the glass while
it is in a fused state, after which the glass so prepared is molded
or blown into the shape or article required. Another process consists
of sprinkling a quantity of the composition over the glass article
while hot, and in a semi-plastic state, by either of which processes a
self-luminous property will be imparted to the article so treated.
Where enamel dials are chipped the cracks may be hidden by first
pressing the cracks very slightly open and washing out. Then work in a
colorless cement to fill the crack, allow to dry and stone down. Where
holes have been left by the chipping, melt equal parts of scraped pure
white wax and zinc white and let it cool. Warm the dial slightly and
press the cold wax into the defective places and scrape off with a
sharp knife and it will leave a white and lustrous surface. If too hard
add wax; if too soft add some zinc white.
VARNISH FOR DIALS, ETC.—A handsome varnish for the dials of clocks,
watches, etc., may be prepared by dissolving bleached shellac in the
purest and best alcohol. It offers the same resistance to atmospheric
influence that common shellac does. In selecting bleached shellac for
this purpose be careful to get that which will dissolve in alcohol, as
some of it being bleached with strong alkalies, is thereby rendered
insoluble in alcohol. The shellac when dissolved should be of a clear
light amber color in the bottle and this will be invisible on white
paper when dry.
Colorless celluloid lacquer, known to jewelers as “silver lacquer”
on account of its being used to prevent tarnish on finished hollow
ware, also makes a good varnish to apply to dials, either metallic or
painted. It is best to have it thin, flow it on the dial and then level
the dial to dry.
Success in the repairing of a broken enameled clock dial will greatly
depend upon the practical skill of the operator, as well as of a
knowledge of the process. If it is only desired to repair a chipped
place on a dial, a fusible enamel of the right tint should be procured
from a dealer in watchmakers’ materials, which, with ordinary care,
may be fused on the chipped place on the dial so as to give it a
workmanlike appearance when finished off. The place to receive the
enamel should be well cleaned, and the moist enamel spread over the
place in a thin, even layer; and, after allowing it to dry, the dial
may be held over a spirit lamp until the new enamel begins to fuse,
when it may be smoothed down with a knife. The dial, after this
operation, is left to cool, when any excess of enamel may be removed by
means of a corundum file, and subsequently polished with putty powder
(oxide of tin). The ingredients of enamel, after being fused into a
mass, are allowed to cool, then crushed to powder and well washed to
get rid of impurities, and the resulting fine powder forms the raw
material for enameling. It is applied to the object to be enameled in a
plastic condition, and is reduced to enamel by the aid of heat, being
first thoroughly dried by gentle heat, and then fused by a stronger
one. The following is a good white enamel for dials:
Silver sand, 3 ounces; red lead, 3¾ ounces; oxide of tin, 2½ ounces;
saltpeter, ½ ounce; borax, 2 ounces, flint glass, 1 ounce; manganese
peroxide, 2 grains. The basis of nearly all enamels is an easily
fusible colorless glass, to which the required opacity and tints are
given by the addition of various metallic oxides, and these, on being
fused together, form the different kinds of vitreous substances used by
enamel workers as the raw material in the art of enameling.
The hands of timekeepers are worthy of more attention than is
frequently bestowed upon them by watch and clockmakers. Their shape
and general arrangement, and the neatness of their execution is often
taken by the general public as an index to the character of the entire
mechanism that moves them; and some are apt to suppose that when care
is not bestowed on the parts of the timepiece which are most seen,
much care cannot be expected to have been exercised on the parts of
the watch or clock which are invisible to the general view. Although
we are not prepared to fully endorse the opinion that when the hands
of timepieces are imperfect in their execution, or in their general
arrangement, all the mechanism must of necessity be imperfect also;
still we think that in many instances there is room for improving the
hands of timepieces, and we desire to direct more attention to this
subject by the workmen.
In the general arrangement of the hands of watches and clocks,
distinctness of observation should be the great point aimed at, and
everything that has a tendency to lead to confusion should be carefully
avoided. Clocks that have a number of hands radiating from one center,
and moving round one circle—as for instance, center seconds, days of
the month, equation of time, alarms and hands for other purposes—may
show a good deal of mechanical skill on the part of the designer and
maker of the timepiece; but so many hands moving together around one
circle, although they may be of different colors, causes confusion,
and requires considerable effort to make out what the different hands
point to in a dim light, and this confusion is frequently increased by
the necessity for a counterpoise being attached to some of the hands.
As a rule timekeepers should be so arranged that never more than the
hour and minute hand should move from one center on the dial. There
may be special occasions when it is necessary or convenient to have
center seconds to large dials; but these occasions are rare, and we are
talking about the hands of timekeepers in everyday use for the ordinary
purposes of life, and also for scientific uses. In astronomical clocks
and watchmakers’ regulators we find the hour, minute and second hands
moving on separate circles on the same dial; and the chief reason
for this arrangement is to prevent mistakes in reading the time. In
chronometers, especially those measuring sidereal time, the hour hand
is frequently suppressed, and the hours are indicated by a star wheel,
or ring, with figures engraved on it, that show through a hole in the
dial.
Hour and minute hands should be shaped so that the one can be easily
distinguished from the other without any effort on the part of the
observer. Probably a straight minute hand, a little swelled near the
point, and a spade hour hand, are the shapes best adapted for this
purpose, especially if the hands have to be looked at from a distance.
There are occasions, however, when a spade hand cannot be used with
propriety. In small watches and clocks having ornamental cases, hands
of other designs are desirable, but whatever be the pattern used, or
whatever color the hands may be made, it should ever be remembered that
while a design in harmony with the case is perfectly admissible, the
sole use of hands is to mark the time distinctly and readily.
The difference in the length of the hour and minute hands is also an
important point in rendering the one easily distinguished from the
other. The extreme point of the hour hand should extend so as to just
cover the edge of the inside end of the numerals and the extreme point
of the minute hand should cover about two-thirds of the length of the
minute divisions. Hands made of this length will be found to mark the
hours and minutes with great plainness, and the rule will be found to
work well in dials of all sizes. As a general rule, the extreme points
of the hands should be narrow. The point of the hour hand should never
be broader than the thickest stroke of any of the numerals, and the
extreme point of the minute hand never broader than the breadth of
the minute lines; and in small work it is well to file the ends of
the hands to a fine point. The ends of minute hands should in every
instance be bent into a short, graceful curve pointing toward the dial,
and as close to it as will just allow the point of the hand to be
free. The minute hands of marine chronometers are invariably bent in
this manner, and the hands of these instruments are usually models of
neatness and distinctness.
Balancing hands by means of a counterpoise is a subject which requires
some attention in order to effect the perfect poise of the hand without
detracting anything from its distinctness. In watch work, and even in
ordinary clock work, it seldom happens that any of the hands except
the seconds require to be balanced, and then there is only one hand
moving round the same circle, as is the case with seconds hands in
general. We have become so accustomed to looking at seconds hands with
projecting tails that we are apt to regard the appearance of the hands
to be incomplete without the usual tail; but we must remember that
the primary object in view in having a tail to a seconds hand is to
counterpoise it, not to improve the looks of the hand itself. Poising
becomes an actual necessity for a hand placed on so sensitive a part
as the fourth wheel of a watch, or on the scape wheel of a fine clock.
When only one hand moves in the same circle, like a seconds hand, the
counterpoise may be effected by means of a projecting tail without in
any way detracting from a distant reading of the hands, providing the
tail is not made too long, and it is made of such a pattern that the
one end can easily be distinguished from the other. In minute and hour
hands, however, it is different. These two hands move round the same
circle, and a counterpoise on the minute hand is liable at a distance
to be mistaken for the hour hand.
The minute hands of large timepieces frequently require to be balanced,
especially if the dial be large in comparison to the size of the
movement; and in very large or tower clocks, whatever may be the size
of the movement, it becomes an absolute necessity to balance the hands.
In our opinion, tails should never be made on minute hands, when they
can be avoided, and in cases where tails cannot be dispensed with,
they should invariably be colored the same as the ground of the dial.
In almost every instance, however, minute hands may be balanced in
the inside, as is usual with tower clocks. A great many clocks used
for railway and similar purposes in Europe have their minute hands
balanced in this manner, and the plan works admirably; for in addition
to rendering the hands more distinct, the clocks require less power to
keep them going than when the hands are balanced from the outside.
[Illustration: Fig. 150. Showing counterpoise on arbor of minute hand
in tower clock.]
Tower clock hands are generally made of copper, elliptical in section,
being made up of two circular segments brazed together at the edges,
with internal diaphragms to stiffen them. The minute hand is straight
and perfectly plain, with a blunt point. At the center of the dial the
width of the minute hand is one-thirteenth of its length, tapering to
about half as much at the point.
The hour hand is about the same width, ending just short of the
dial figure and terminating in a palm or ornament. The external
counterpoises are one-third the length of the minute hand, and of such
a shape that they will not be confounded with either of the hands; a
cylinder, painted the same color as the dial, and loaded with lead,
makes a good counterpoise. This counterpoise may be partly on the
inside of the dial if it is desired to keep it invisible, but it should
not be omitted, as it saves a good deal of power, prevents the twisting
of the arbors, and also assists in overcoming the action of the wind
on the hands. Two-thirds of the counterpoise weight may be inside, as
shown in Fig. 150.
TO BLUE A CLOCK HAND OR A SPRING.—To blue a piece of steel that is of
some length, a clock hand for example, clockmakers place it either
on ignited charcoal, with a hole in the center for the socket, and
whitened over its surface, as this indicates a degree of heat that is
approximately uniform, or on a curved bluing tray perforated with holes
large enough to admit the socket. The center will become violet or blue
sooner than the rest, and as soon as it assumes the requisite tint,
the hand must be removed, holding it with tweezers by the socket, or
by the aid of a large sized arbor passed through it; the lower side of
the hand is then placed on the edge of the charcoal or bluing tray,
and removed by gradually sliding it off toward the point, more or less
slowly, according to the progress made with the coloring; with a little
practice, the workman will soon be enabled to secure a uniform blue
throughout the length and even, if necessary, to retouch parts that
have not assumed a sufficiently deep tint.
Instead of a bluing tray, a small mass of iron, with a slightly rounded
surface and heated to a suitable temperature, can be employed; but the
color must not form too rapidly, and this is liable to occur if the
temperature of the mass is excessive. Nor should this temperature be
unevenly distributed.
A spring, after being whitened, can be blued in the same way. Having
fixed one end, it is stretched by a weight attached to the other end,
and the hot iron is then passed along it at such a speed that a uniform
color is secured. Of course, the hot iron might be fixed and the spring
passed over it. A lamp may be used, but its employment involves more
attention and dexterity.