A Treatise on Staff Making and Pivoting
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Eugene E. Hall >> A Treatise on Staff Making and Pivoting
Transcriber's notes:
Some minor typographical errors have been corrected.
The author's spelling has been retained.
A TREATISE
ON
STAFF MAKING
AND
PIVOTING
CONTAINING COMPLETE DIRECTIONS FOR MAKING
AND FITTING NEW STAFFS FROM
THE RAW MATERIAL
EUGENE E. HALL
WITH NUMEROUS ILLUSTRATIONS
CHICAGO:
HAZLITT & WALKER, PUBLISHERS
1910
CONTENTS.
CHAPTER I.
The raw material. The gravers. The roughing out. The hardening
and tempering 5
CHAPTER II.
Kinds of pivots. Their shape. Capillarity. The requirements of
a good pivot 13
CHAPTER III.
The proper measurements and how obtained 19
CHAPTER IV.
The gauging of holes. The side shake. The position of the graver 23
CHAPTER V.
The grinding and polishing. The reversal of the work. The wax
chuck 29
CHAPTER VI.
Another wax chuck. The centering of the work 35
CHAPTER VII.
The finishing of the staff. Pivoting. Making pivot drills. Hardening
drills. The drilling and fitting of new pivots 39
STAFF MAKING AND PIVOTING.
CHAPTER I.
To produce a good balance staff requires more skill than to produce any
other turned portion of a watch, and your success will depend not alone
on your knowledge of its proper shape and measurements, nor the tools at
your command, but rather upon your skill with the graver and your success
in hardening and tempering. There are many points worthy of consideration
in the making of a balance staff that are too often neglected. I have
seen staffs that were models as regards execution and finish, that were
nearly worthless from a practical standpoint, simply because the maker
had devoted all his time and energy to the execution of a beautiful piece
of lathe work, and had given no thought or study to the form and size of
the pivots. On the other hand, one often sees staffs whose pivots are
faultless in shape, but the execution and finish so bungling as to offset
all the good qualities as regards shape. To have good tools and the right
ideas is one thing, and to use these tools properly and make a practical
demonstration of your theory is another.
I shall endeavor to take up every point in connection with the balance
staff, from the steel to the jewels, and their relation to the pivots,
and I believe this will then convey to the reader all the necessary
points, not only as regards staffs, but pivots also, whether applied to a
balance or a pinion staff.
It may be argued, and we often do hear material dealers advance the
theory, that to-day, with our interchangeable parts and the cheapness of
all material, it is a waste of time to make a balance staff. To the
reader who takes this view of the situation I simply want to say, kindly
follow me to the end of this paragraph, and if you are still of the same
opinion, then you are wasting your time in following me farther. For a
material dealer to advance this theory I can find some excuse; he is an
interested party, and the selling of material is his bread and butter;
but the other fellow, well I never could understand him and possibly
never shall. When we seriously consider the various styles and series in
"old model" and "new model," of only one of the leading manufacturers of
watches in this country, to say nothing of the legion of small and large
concerns who are manufacturing or have manufactured in the past, and then
think of carrying these staffs in stock, all ready for use, we then begin
to realize how utterly absurd the idea is, to say nothing of how
expensive! On the other hand, if you reside in a large city and propose
to rely on the stock of your material dealer, you will find yourself in
an embarrasing situation very often, for as likely as not the movement
requiring a new staff was made by a company that went out of business
back in the '80s, or it is a new movement, the material for which has
not yet been placed on the market. This state of affairs leads to
makeshifts, and they in turn lead to botch work. The watchmaker who does
not possess the experience or necessary qualifications to make a new
balance staff and make it in a neat and workmanlike manner, is never
certain of having exactly what is needed, and cannot hope to long retain
the confidence of his customers. In fact, he is not a watchmaker at all,
but simply an apprentice or student, even though he be working for a
salary or be his own master. There are undoubtedly many worthy members of
the trade, who are not familiar with the making of a balance staff, who
will take exceptions to this statement; but it is nevertheless true. They
may be good workmen as far as they go; they may be painstaking; but they
cannot be classed as watchmakers.
This article is intended for the benefit of that large class whose
opportunities for obtaining instruction are limited, and who are ready
and willing to learn, and for that still larger class of practical
workmen who can make a new staff in a creditable manner, but who are
always glad to read others people's ideas on any subject connected with
the trade and who are not yet too old to learn new tricks should they
find any such.
[Illustration: _Fig. 1._]
Good tools, in good condition, are the most essential requisites in
making a new staff. I would not advise any particular make of lathe, as
the most expensive lathe in the world will not produce a true staff if
the workman cannot center his work accurately and does not know how to
handle his graver, while on the other hand fine work can be done on the
simplest and cheapest lathe by a workman possessing the requisite skill.
I will take it for granted that you use an American-made lathe of some
kind, or a foreign-made lathe manufactured on American lines. It is
advisable, though not absolutely necessary, to have three gravers similar
to those illustrated in Fig. 1, A being used for turning the staff down
in the rough; B for the conical pivots and square shoulders and C for the
under-cutting. The other tools and attachments needed will be described
as I come to them in use.
The balance staff should be made of the best steel, tempered to such a
degree as to give the longest service and yet not so hard as to endanger
the breakage of the pivots. Select a piece of Stubb's steel wire, say No.
46, or a little larger than the largest part of the finished staff is to
be, and center it in a split chuck of your lathe. Be careful in selecting
your chuck that you pick one that fits the wire fairly close. The chuck
holds the work truest that comes the nearest to fitting it. If you try to
use a chuck that is too large or too small for the work, you will only
ruin the chuck for truth. Turn the wire to the form of a rough staff, as
shown in Fig. 2, leaving on a small part of the original wire, as shown
at A. After the wire is roughed out to this general form, remove from the
chuck and get ready to harden and temper it. The hardening and tempering
may be effected in various ways, and I am scarcely prepared to say which
method is the best, as there are several which give about the same
general results. One method of hardening is to smear the blank with
common yellow soap, heat it to a cherry red, and drop endwise into
linseed oil. Petroleum is preferred by some to linseed oil, but, to tell
the truth, I can see no difference in the action of linseed, petroleum or
olive oil. Be sure and have enough oil to thoroughly cool the blank, and
a deep vessel, such as a large-mouthed vial, is preferable to a saucer.
The blank will now be found too hard to work easily with the graver, and
we must therefore draw the temper down to that of fine spring steel.
Before doing this the blank should be brightened, in order that we may
see to just what color we are drawing it. The main object in using the
soap in hardening is that it may form a scale upon the blank, and if the
heating is effected gradually the soap will melt and form a practically
air-tight case around the blank. This scale, if the hardening is
carefully and properly done, will generally chip and fall off when the
blank is plunged in the oil, particularly if the oil is cool, and if it
does not fall off of its own accord, it can easily be removed by rolling
the blank upon the bench. If it does not come out clean, or if soap is
not used, it may be brightened by again inserting in the lathe and
bringing it in contact with a piece of fine emery paper or cloth.
[Illustration: _Fig. 2._]
I draw the temper in the following manner: Place some fine brass filings
in a boiling-out cup or bluing pan and lay the blank upon these filings,
holding the pan over the flame of an alcohol lamp until the blank assumes
a dark purple color, which it will reach when the heat gets to about 500 deg.
F. This I consider the right hardness for a balance staff, as it is not
too hard to work well under the graver nor too soft for the pivots. At
this degree of hardness steel will assume an exquisite polish if properly
treated. Another method of tempering is to place the staff on a piece of
sheet iron or copper (say 1 inch wide by 4 long), having previously bent
it into a small angle, for the reception of the staff, as shown in Fig.
3. This piece of metal, when nicely fitted into a file handle, will
answer all the purposes of the bluing pan and presents quite a neat
appearance. Having placed the blank in the angle, lay on it a piece of
yellow wax about the size of a bean, and heat it over your lamp until the
wax takes fire and burns. Blow out the flame and allow the staff to cool,
and it will be found to be of about the right hardness.
[Illustration: _Fig. 3._]
We have now arrived at an important station in staff making, a junction,
we may term it, where many lines branch off from the main road. At this
particular spot is where authorities differ. I have no hesitation in
saying that at this particular point the split chuck should be removed
from the lathe head and carefully placed in the chuck box and the cement
chuck put in its place. I believe that all of the remaining work upon a
staff should be executed while it is held in a cement chuck. On the other
hand I have seen good workmen who turned and finished all the lower part
of a staff while in a split chuck, cut it off and turned and finished the
upper part in a cement chuck. All I have got to say is that they had more
confidence in the truth of their chucks than I have in mine. I have even
read of watchmakers who made the entire staff in a split chuck, but I
must confess I am somewhat curious to examine a staff made in that way,
and must have the privilege of examining it before I will admit that a
true staff can be so made.
We will suppose that the workman has a moderately true chuck, and that he
prefers to turn and finish all the lower portions in this way. Of course
the directions for using a cement chuck on the upper part of a staff are
equally applicable to the lower. Before going further I think it
advisable to consider the requirements of a pivot, but will reserve this
for another chapter.
CHAPTER II.
The chief requirements of a pivot are that it shall be round and well
polished. Avoid the burnish file at all hazards; it will not leave the
pivot round, for the pressure is unequal at various points in the
revolution. A pivot that was not perfectly round might act fairly well in
a jewel hole that was round, but unfortunately the greater proportion of
jewel holes are not as they should be, and we must therefore take every
precaution to guard against untrue pivots. Let us examine just what the
effect will be if an imperfect pivot is fitted into an unround hole
jewel, and to demonstrate its action more clearly let us exaggerate the
defects. Suppose we pick a perfectly round jewel and insert into the
opening a three-cornered piece of steel wire, in shape somewhat
resembling the taper of a triangular file. We find that this triangular
piece of steel will turn in the jewel with the same ease that the most
perfect cylindrical pivot will. Now suppose we change the jewel for one
that is out of round and repeat the experiment. We now find that the
triangular steel soon finds the hollow spots in the jewel hole and comes
to a stand-still as it is inserted in the hole. The action of a pivot
that is not true, when in contact with a jewel whose hole is out of
round, is very similar, though in a less marked degree. If the pivot
inclines toward the elliptical and the jewel hole has a like failing,
which is often the case, it is very evident that this want of truth in
both the pivot and hole is very detrimental to the good going of a watch.
[Illustration: _Fig. 4._]
[Illustration: _Fig. 5._]
There are two kinds of pivots, known respectively as straight and conical
pivots, but for the balance staff there is but one kind and that is the
conical, which is illustrated in Fig. 4. The conical pivot has at least
one advantage over the straight one, _i. e._, it can be made much smaller
than a straight pivot, as it is much stronger in proportion, owing to its
shape. All pivots have a tendency to draw the oil away from the jewels,
and particularly the conically formed variety, which develops a strong
capillary attraction. To prevent this capillary attraction of the oil,
the back-slope is formed next to the shoulder, although many persons seem
to think that this back-slope is merely added by way of ornament, to make
the pivot more graceful in appearance. It is very essential, however, for
if too much oil is applied the staff would certainly draw it away if its
thickness were not reduced, by means of the back-slope. Before leaving
the subject of capillarity let us examine the enlarged jewel in Fig. 5;
_c_ is an enlarged pivot, _b_ is the hole jewel and _a_ is the end stone.
We observe that the hole jewel on the side towards the end stone is
convex. It is so made that through capillarity the oil is retained at
the end of the pivot where it is most wanted. It is, in my opinion, very
necessary that the young watchmaker should have at least a fair
understanding of capillarity, and should understand why the end stone is
made convex and the pivot with a back slope. For this reason I will try
and make clear this point before proceeding further. We all know that it
is essential to apply oil to all surfaces coming in contact, in order to
reduce the friction as much as possible, and if the application of oil is
necessary to any part of the mechanism of a watch, that part is the
pivot. Saunier very aptly puts it thus: "A liquid is subject to the
action of three forces: gravity, adhesion (the mutual attraction between
the liquid and the substance of the vessel containing it), and cohesion
(the attractive force existing among the molecules of the liquid and
opposing the subdivision of the mass.)"
We all know that if we place a small drop of oil upon a piece of flat
glass or steel and then invert the same the oil will cling to the glass,
owing to the adhesion of the particles; if we then add a little more to
the drop and again invert, it will still cling, although the drop may be
elongated to a certain degree. This is owing to the cohesion of the
molecules of the oil, which refuse to be separated from one another. If,
however, we again add to the drop of oil and invert the plate the drop
will elongate and finally part, one portion dropping while the other
portion clings to the main body of the liquid. The fall of the drop is
occasioned by gravity overcoming the cohesion of the molecules. Now take
a perfectly clean and polished needle and place a drop of oil upon its
point and we will see that the oil very rapidly ascends towards the
thicker portion of the needle. Now if we heat and hammer out the point of
the needle into the form of a small drill and repeat the operation we
find that the oil no longer ascends. It rises from the point to the
extreme width of the drill portion, but refuses to go beyond. It clings
to that portion of the needle which would correspond to the ridge just
back of the slope in a conical pivot. Water, oil, etc., when placed in a
clean wine glass, do not exhibit a perfectly level surface, but raise at
the edges as shown at _a_ in Fig. 6. If a tube is now inserted, we find
that the liquid not only rises around the outside of the tube and the
edges of the vessel, but also rises in the tube far beyond its mean
level, as shown at _b_. These various effects are caused by one of the
forces above described, _i. e._, the adhesion, or mutual attraction
existing between the liquid and the substance of the vessel and rod. The
word capillarity is of Latin derivation, and signifies hair-like
slenderness. The smaller the tube, or the nearer the edges of a vessel
are brought together, the higher in proportion will the liquid rise above
the level. An ascent of a liquid, due to capillarity, also takes place,
where the liquid is placed between two separate bodies, as oil placed
between two pieces of flat glass. If the plates are parallel to one
another and perpendicular to the surface of the liquid it will ascend to
the same height between the plates, as shown at _c_ in Fig. 6. If the
plates were united at the back like a book and spread somewhat at the
front, the oil would ascend the higher as the two sides approach one
another, as shown at _d_, Fig. 6. If a drop is placed somewhat away from
the intersecting point, of the glasses, as shown at _m_ it will, if not
too far away, gradually work its way to the junction, providing the
glasses are level. If, however, the glasses are inclined to a certain
extent, the drop will remain stationary, since it is drawn in one
direction by gravity and in the other by capillarity. When a drop of oil
is placed between two surfaces, both of which are convex, or one convex
and the other plain, as shown at _g_, it will collect at the point _n_,
at which the surfaces nearest approach one another. We now see very
clearly why the hole jewel is made convex on the side towards the
end-stone and concave on the side towards the pivot.
[Illustration: _Fig. 6._]
Particular pains should be taken to polish those portions of the pivots
which actually enter the jewel hole and to see that all marks of the
graver be thoroughly removed, because if any grooves, no matter how
small, are left, they act as minute capillary tubes to convey the oil.
If the hole jewel be of the proper shape, the end-stone not too far from
the hole jewel and too much oil is not applied at one time, the oil will
not spread nor run down the staff, but a small portion will be retained
at the acting surface of pivot and jewel, and this supply will be
gradually fed to these parts from the reservoir between the jewel and
end-stone, by the action of capillarity.
Having examined into the requirements of the pivot and its jewel and
having gained an insight into what their forms should be, we are the
better able to perform that portion of the work in an intelligent
manner.
CHAPTER III.
Our wire has been roughed out into the form of a staff, has been hardened
and the temper drawn down to the requisite hardness and we are now ready
to proceed with our work. As I said before, we have now arrived at a
point where many authorities differ, _i. e._, as to whether the finishing
of the staff proper, should be performed while the work is held in the
chuck, or whether a wax chuck be substituted. We will take it for granted
that you have a true chuck and that you prefer to finish all the lower
portion of the staff while held in the chuck.
Before we proceed with our work it will be necessary for us to make some
accurate measurements, as we cannot afford to do any guess work by
measuring by means of the old staff. I have used a number of different
kinds of calipers and measuring instruments for determining the various
measurements for a balance staff, but have met with more success with a
very simple little tool which I made myself from drawings and description
published some years ago in THE AMERICAN JEWELER. This simple little tool
is shown in Fig. 7, and has been of great service to me. It consists of a
brass sleeve A, with a projection at one end as shown at B. This sleeve
is threaded, and into it is fitted the screw part C, which terminates in
a pivot D, which is small enough to enter the smallest jewel. The sleeve
I made from a solid piece of brass, turning it down in my lathe and
finishing the projection by means of a file. The hole was then drilled
and threaded with a standard thread. The screw part C, I made of steel
and polished carefully.
[Illustration: _Fig. 7._]
To ascertain the proper height for the roller, place it upon the tool,
allowing it to rest upon the leg B, and set the pivot D in the foot
jewel. Now adjust, by means of the screw C until the roller is in its
proper position in relation to the lever fork. This may be understood
better by consulting Fig. 8, where A is the gauge, C is the roller, E is
the lever, F is the plate and G is the potance.
[Illustration: _Fig. 8._]
Now in order to locate the proper place to cut the seat for the roller,
remove it from the foot of the gauge and apply the gauge to the work as
shown in Fig. 9. The foot of the gauge resting against the end of the
pivot, the taper end of the gauge will locate accurately the position of
the roller seat. In order to locate the proper position for the seat for
the balance, proceed the same as for the roller, except that the foot of
the gauge is lowered until it is brought sufficiently below the plate to
allow of the proper clearance as indicated by the dotted lines at H. Now
apply the gauge to the new staff, as shown in Fig. 10, and the taper end
will locate the exact position for the balance seat.
[Illustration: _Fig. 9._]
[Illustration: _Fig. 10._]
As previously stated, I have taken it for granted that you preferred to
finish all the lower portion of the staff while the work was held in the
chuck. I have assumed that you prefer to work in this way because I have
noted the fact that nine watchmakers out of every ten start with, and
first finish up, the lower portion of the staff. Where this method of
working originated I do not know, but it always has the appearance to me
of "placing the cart before the horse." I do not pretend to say that a
true staff cannot be made in this way, but it certainly is not the most
convenient nor advisable. We all know that the heaviest part of the staff
is from the roller seat to the end of the top pivot. Now it seems to me
that it is the most natural thing in the world for a mechanic to desire
to turn the greater bulk of his work before reversing it. Now if the
workman has been educated to turn indifferently with right or left hand,
it may make little difference, as far as the actual turning is concerned,
whether he starts to work at the upper or lower end of the staff, but
unfortunately there are few among us who are so skilled as to use the
graver with equal facility with either hand, and it is therefore an
advantage to start with the upper end, as you can thus finish a greater
portion of the work more readily. You can readily see that when you come
to reverse your staff and use the wax chuck, that by starting at the top
of staff your wax has a much larger surface of metal to cling to, and
again the shape of the balance seat is such as to secure the work firmly
in the wax, while if the reverse method is employed, the larger portion
of the balance seat is exposed and the staff is more liable to loosen
from the motion of the lathe and pressure of the graver and polishers.
CHAPTER IV.
By the aid of the pinion calipers and the old staff, the diameter of the
roller seat and the balance and hair-spring collet seats may be readily
taken, but it is perhaps better to gauge the holes, as the old staff may
not have been perfect in this respect. A round broach will answer
admirably for this purpose, and the size may be taken from the broach by
means of the calipers. In fitting our pivots, we can not be too exact;
and as yet no instrument has been placed upon the market for this purpose
which is moderate in price and yet thoroughly reliable. The majority of
watchmakers use what is termed the pivot-gauge, a neat little instrument
which accompanies the Jacot lathe, and which may be obtained from any
material house. This tool, which is shown in Fig. 11, is, however, open
to one objection in the measurement of pivots, and that is that it may be
pressed down at one time with greater force than at another, and
consequently will show a variation in two measurements of the same pivot.
Some of my readers may think that I am over-particular on this point, and
that the difference in measurement on two occasions is too trivial to be
worthy of attention, but I do not think that too much care can be
bestowed upon this part of the work, and neglect in this particular is,
I think, the cause of poor performance in many otherwise good
timepieces. The ordinarily accepted rule among watchmakers is that a
pivot should be made 1/2500 of an inch smaller than the hole in the jewel
to allow for the proper lubrication. I am acquainted with watchmakers,
and men who are termed good workmen, too, who invariably allow 1/2500 of
an inch side shake, no matter whether the pivot is 12/2500 or 16/2500 of
an inch in diameter. Now if 1/2500 of an inch is the proper side shake
for a pivot measuring 12/2500 of an inch in diameter, it is certainly not
sufficient for a pivot which is one-third larger. Of course it is
understood that side shakes do not increase in proportion according as
the pivot increases in size, for if they did a six-inch shaft would
require at this rate a side shake of 1/2 inch, or 1/4 inch on each side,
which would be ridiculously out of all proportion, as the 1/64 of an inch
would be ample under any circumstances. Neither can we arrive at the
proper end shake for a pivot by reducing in proportion from the end shake
allowed on a six-inch shaft, because if we followed out the same course
of reasoning we would arrive at a point where a pivot measuring 12/2500
of an inch would require an end shake so infinitely small that it would
require six figures to express the denominator of the fraction, and the
most minute measuring instrument yet invented would be incapable of
recording the measurement. We must leave sufficient side shake, however,
on the smallest pivot and jewel for the globules of the oil to move
freely, and experiments have shown conclusively that 1/2500 of an inch or
1/5000 on each side of the pivot, is as little space as it is desirable
to leave for that purpose, as the globules of the best chronometer oil
will refuse to enter spaces that are very much more minute. But to return
to our pivot gauge.