Watch and Clock Escapements Part 5

HOW FLAT STEEL POLIs.h.i.+NG IS DONE.

Polis.h.i.+ng a regulator bar for a large model, such as we are building, is only a heavy job of flat steel work, a little larger but no more difficult than to polish a regulator for a sixteen-size watch. We would ask permission here to say that really nice flat steel work is something which only a comparatively few workmen can do, and, still, the process is quite simple and the accessories few and inexpensive. First, ground-gla.s.s slab 6" by 6" by "; second, flat zinc piece 3" by 3" by "; third, a piece of thick sheet bra.s.s 3" by 2" by 1/8"; and a bottle of Vienna lime. The gla.s.s slab is only a piece of plate gla.s.s cut to the size given above. The zinc slab is pure zinc planed dead flat, and the gla.s.s ground to a dead surface with another piece of plate gla.s.s and some medium fine emery and water, the whole surface being gone over with emery and water until completely depolished. The regulator bar, after careful filing and dressing up on the edges with an oilstone slip or a narrow emery buff, is finished as previously described. We would add to the details already given a few words on polis.h.i.+ng the edges.

[Ill.u.s.tration: Fig. 47]

It is not necessary that the edges of steelwork, like the regulator bar _B_, Fig. 47, should be polished to a flat surface; indeed, they look better to be nicely rounded. Perhaps we can convey the idea better by referring to certain parts: say, spring to the regulator, shown at _D_, Fig. 40, and also the hairspring stud _E_. The edges of these parts look best beveled in a rounded manner.

[Ill.u.s.tration: Fig. 48]

[Ill.u.s.tration: Fig. 49]

It is a little difficult to convey in words what is meant by "rounded"

manner. To aid in understanding our meaning, we refer to Figs. 48 and 49, which are transverse sections of _D_, Fig. 50, on the line _f_. The edges of _D_, in Fig. 48, are simply rounded. There are no rules for such rounding--only good judgment and an eye for what looks well. The edges of _D_ as shown in Fig. 49 are more on the beveled order. In smoothing and polis.h.i.+ng such edges, an ordinary jeweler's steel burnish can be used.

[Ill.u.s.tration: Fig. 50]

SMOOTHING AND POLIs.h.i.+NG.

The idea in smoothing and polis.h.i.+ng such edges is to get a fair gloss without much attention to perfect form, inasmuch as it is the flat surface _d_ on top which produces the impression of fine finish. If this is flat and brilliant, the rounded edges, like _g c_ can really have quite an inferior polish and still look well. For producing the flat polish on the upper surface of the regulator bar _B_ and spring _D_, the flat surface _d_, Figs. 48, 49, 51 and 52, we must attach the regulator bar to a plate of heavy bra.s.s, as shown at Fig. 47, where _A_ represents the bra.s.s plate, and _B_ the regulator bar, arranged for grinding and polis.h.i.+ng flat.

[Ill.u.s.tration: Fig. 51]

[Ill.u.s.tration: Fig. 52]

For attaching the regulator bar _B_ to the bra.s.s plate _A_, a good plan is to cement it fast with lathe wax; but a better plan is to make the plate _A_ of heavy sheet iron, something about 1/8" thick, and secure the two together with three or four little catches of soft solder. It is to be understood the edges of the regulator bar or the regulator spring are polished, and all that remains to be done is to grind and polish the flat face.

Two pieces _a a_ of the same thickness as the regulator bar are placed as shown and attached to _A_ to prevent rocking. After _B_ is securely attached to _A_, the regulator should be coated with sh.e.l.lac dissolved in alcohol and well dried. The object of this sh.e.l.lac coating is to keep the angles formed at the meeting of the face and side clean in the process of grinding with oilstone dust and oil. The face of the regulator is now placed on the ground gla.s.s after smearing it with oil and oilstone dust. It requires but a very slight coating to do the work.

The grinding is continued until the required surface is dead flat, after which the work is washed with soap and water and the sh.e.l.lac dissolved away with alcohol. The final polish is obtained on the zinc lap with Vienna lime and alcohol. Where lathe cement is used for securing the regulator to the plate _A_, the alcohol used with the Vienna lime dissolves the cement and smears the steel. Diamantine and oil are the best materials for polis.h.i.+ng when the regulator bar is cemented to the plate _A_.

KNOWLEDGE THAT IS MOST ESSENTIAL.

_The knowledge most important for a practical working watchmaker to possess is how to get the watches he has to repair in a shape to give satisfaction to his customers._ No one will dispute the truth of the above italicised statement. It is only when we seek to have limits set, and define what such knowledge should consist of, that disagreement occurs.

One workman who has read Grossmann or Saunier, or both, would insist on all watches being made to a certain standard, and, according to their ideas, all such lever watches as we are now dealing with should have club-tooth escapements with equidistant lockings, ten degrees lever and pallet action, with one and one-half degrees lock and one and one-half degrees drop. Another workman would insist on circular pallets, his judgment being based chiefly on what he had read as stated by some author. Now the facts of the situation are that lever escapements vary as made by different manufacturers, one concern using circular pallets and another using pallets with equidistant lockings.

WHAT A WORKMAN SHOULD KNOW TO REPAIR A WATCH.

One escapement maker will divide the impulse equally between the tooth and pallet; another will give an excess to the tooth. Now while these matters demand our attention in the highest degree in a theoretical sense, still, for such "know hows" as count in a workshop, they are of but trivial importance in practice.

We propose to deal in detail with the theoretical consideration of "thick" and "thin" pallets, and dwell exhaustively on circular pallets and those with equidistant locking faces; but before we do so we wish to impress on our readers the importance of being able to free themselves of the idea that all lever escapements should conform to the rigid rules of any dictum.

EDUCATE THE EYE TO JUDGE OF ANGULAR AS WELL AS LINEAR EXTENT.

For ill.u.s.tration: It would be easy to design a lever escapement that would have locking faces which were based on the idea of employing neither system, but a compromise between the two, and still give a good, sound action. All workmen should learn to estimate accurately the extent of angular motion, so as to be able to judge correctly of escapement actions. It is not only necessary to know that a club-tooth escapement should have one and one-half degrees drop, but the eye should be educated, so to speak, as to be able to judge of angular as well as linear extent.

[Ill.u.s.tration: Fig. 53]

Most mechanics will estimate the size of any object measured in inches or parts of inches very closely; but as regards angular extent, except in a few instances, we will find mechanics but indifferent judges. To ill.u.s.trate, let us refer to Fig. 53. Here we have the base line _A A'_ and the perpendicular line _a B_. Now almost any person would be able to see if the angle _A a B_ was equal to _B a A'_; but not five in one hundred practical mechanics would be able to estimate with even tolerable accuracy the measure the angles made to the base by the lines _b c d_; and still watchmakers are required in the daily practice of their craft to work to angular motions and movements almost as important as to results as diameters.

What is the use of our knowing that in theory an escape-wheel tooth should have one and one-half degrees drop, when in reality it has three degrees? It is only by educating the eye from carefully-made drawings; or, what is better, constructing a model on a large scale, that we can learn to judge of proper proportion and relation of parts, especially as we have no convenient tool for measuring the angular motion of the fork or escape wheel. Nor is it important that we should have, if the workman is thoroughly "booked up" in the principles involved.

As we explained early in this treatise, there is no imperative necessity compelling us to have the pallets and fork move through ten degrees any more than nine and one-half degrees, except that experience has proven that ten degrees is about the right thing for good results. In this day, when such a large percentage of lever escapements have exposed pallets, we can very readily manipulate the pallets to match the fork and roller action. For that matter, in many instances, with a faulty lever escapement, the best way to go about putting it to rights is to first set the fork and roller so they act correctly, and then bring the pallets to conform to the angular motion of the fork so adjusted.

FORK AND ROLLER ACTION.

Although we could say a good deal more about pallets and pallet action, still we think it advisable to drop for the present this particular part of the lever escapement and take up fork and roller action, because, as we have stated, frequently the fork and roller are princ.i.p.ally at fault.

In considering the action and relation of the parts of the fork and roller, we will first define what is considered necessary to const.i.tute a good, sound construction where the fork vibrates through ten degrees of angular motion and is supposed to be engaged with the roller by means of the jewel pin for thirty degrees of angular motion of the balance.

There is no special reason why thirty degrees of roller action should be employed, except that experience in practical construction has come to admit this as about the right arc for watches of ordinary good, sound construction. Manufacturers have made departures from this standard, but in almost every instance have finally come back to pretty near these proportions. In deciding on the length of fork and size of roller, we first decide on the distance apart at which to place the center of the balance and the center of the pallet staff. These two points established, we have the length of the fork and diameter of the roller defined at once.

HOW TO FIND THE ROLLER DIAMETER FROM THE LENGTH OF THE FORK.

To ill.u.s.trate, let us imagine the small circles _A B_, Fig. 54, to represent the center of a pallet staff and balance staff in the order named. We divide this s.p.a.ce into four equal parts, as shown, and the third s.p.a.ce will represent the point at which the pitch circles of the fork and roller will intersect, as shown by the arc _a_ and circle _b_.

Now if the length of the radii of these circles stand to each other as three to one, and the fork vibrates through an arc of ten degrees, the jewel pin engaging such fork must remain in contact with said fork for thirty degrees of angular motion of the balance.

[Ill.u.s.tration: Fig. 54]

Or, in other words, the ratio of angular motion of two _mobiles_ acting on each must be in the same ratio as the length of their radii at the point of contact. If we desire to give the jewel pin, or, in ordinary horological phraseology, have a greater arc of roller action, we would extend the length of fork (say) to the point _c_, which would be one-fifth of the s.p.a.ce between _A_ and _B_, and the ratio of fork to roller action would be four to one, and ten degrees of fork action would give forty degrees of angular motion to the roller--and such escapements have been constructed.

WHY THIRTY DEGREES OF ROLLER ACTION IS ABOUT RIGHT.

Now we have two sound reasons why we should not extend the arc of vibration of the balance: (_a_) If there is an advantage to be derived from a detached escapement, it would surely be policy to have the arc of contact, that is, for the jewel pin to engage the fork, as short an arc as is compatible with a sound action. (_b_) It will be evident to any thinking mechanic that the acting force of a fork which would carry the jewel pin against the force exerted by the balance spring through an arc of fifteen degrees, or half of an arc of thirty degrees, would fail to do so through an arc of twenty degrees, which is the condition imposed when we adopt forty degrees of roller action.

For the present we will accept thirty degrees of roller action as the standard. Before we proceed to delineate our fork and roller we will devote a brief consideration to the size and shape of a jewel pin to perform well. In this matter there has been a broad field gone over, both theoretically and in practical construction. Wide jewel pins, round jewel pins, oval jewel pins have been employed, but practical construction has now pretty well settled on a round jewel pin with about two-fifths cut away. And as regards size, if we adopt the linear extent of four degrees of fork or twelve degrees of roller action, we will find it about right.

HOW TO SET A FORK AND ROLLER ACTION RIGHT.

As previously stated, frequently the true place to begin to set a lever escapement right is with the roller and fork. But to do this properly we should know when such fork and roller action is right and safe in all respects. We will see on a.n.a.lysis of the actions involved that there are three important actions in the fork and roller functions: (_a_) The fork imparting perfect impulse through the jewel pin to the balance. (_b_) Proper unlocking action. (_c_) Safety action. The last function is in most instances sadly neglected and, we regret to add, by a large majority of even practical workmen it is very imperfectly understood. In most American watches we have ample opportunity afforded to inspect the pallet action, but the fork and roller action is placed so that rigid inspection is next to impossible.

The Vacheron concern of Swiss manufacturers were acute enough to see the importance of such inspection, and proceeded to cut a circular opening in the lower plate, which permitted, on the removal of the dial, a careful scrutiny of the action of the roller and fork. While writing on this topic we would suggest the importance not only of knowing how to draw a correct fork and roller action, but letting the workman who desires to be _au fait_ in escapements delineate and study the action of a faulty fork and roller action--say one in which the fork, although of the proper form, is too short, or what at first glance would appear to amount to the same thing, a roller too small.

Drawings help wonderfully in reasoning out not only correct actions, but also faulty ones, and our readers are earnestly advised to make such faulty drawings in several stages of action. By this course they will educate the eye to discriminate not only as to correct actions, but also to detect those which are imperfect, and we believe most watchmakers will admit that in many instances it takes much longer to locate a fault than to remedy it after it has been found.

[Ill.u.s.tration: Fig. 55]

Let us now proceed to delineate a fork and roller. It is not imperative that we should draw the parts to any scale, but it is a rule among English makers to let the distance between the center of the pallet staff and the center of the balance staff equal in length the chord of ninety-six degrees of the pitch circle of the escape wheel, which, in case we employ a pitch circle of 5" radius, would make the distance between _A_ and _B_, Fig. 55, approximately 7", which is a very fair scale for study drawings.

HOW TO DELINEATE A FORK AND ROLLER.

To arrive at the proper proportions of the several parts, we divide the s.p.a.ce _A B_ into four equal parts, as previously directed, and draw the circle _a_ and short arc _b_. With our dividers set at 5", from _B_ as a center we sweep the short arc _c_. From our arc of sixty degrees, with a 5" radius, we take five degrees, and from the intersection of the right line _A B_ with the arc _c_ we lay off on each side five degrees and establish the points _d e_; and from _B_ as a center, through these points draw the lines _B d'_ and _B e'_. Now the arc embraced between these lines represents the angular extent of our fork action.