Know Your Product

Part 5, The Escape Department, The Watch Word, April 1936

Albert M. Oslock

Editor's Note - This is the fifth of a series of articles on the manufacture of a watch as conducted in the factory of The Elgin National Watch Company. It is our hope to acquaint our readers with the work of departments other than their own.

In discussing the escapement, which is made in the Escape department, we will consider the escape wheel, pallet, balance, and hairspring. The function of the escapement is to transmit power to the balance, thus keeping it in motion; also, to control the rate, through the action of the balance and hairspring, at which the train wheels of the watch are allowed to rotate or run down. It can now be understood, that if we control the rotation of the center wheel and arbor, to which the minute hand is attached, in such a manner as to cause it to make exactly one revolution per hour, perfect time will be indicated.

The hairspring is made from special steel wire which is .01 inch in diameter, and comes in coils 3000 to 3500 feet in length. This wire is made from Swedish ore, and every coil is tested by the Research department before it is put into process. The first operation is the placing of one of these coils of wire on a reel, then winding it on to a cylindrical drum. It is now placed in a cleaning machine and passed over several rotating rolls, or laps, which are charged with fine emery powder. This removes all scale and foreign matter, leaving the wire perfectly smooth and ready for drawing. The wire must now be drawn to the proper diameter for each size of hairspring, and this is accomplished by passing it through as many as thirty various sizes of diamond dies, each die reducing the wire a very small fractional part of an inch until the desired diameter is obtained. After flattening the wire to the proper dimensions by rolling it between hardened steel rolls, it is sent to the heat treating department where it is hardened and tempered. Now, it is again put through a cleaning process similar to the one previously described and is ready for the finishing operation.

Albert M. Oslock
foreman of the Escape Department

We now have the wire in the form of a flat ribbon, and our next operation is to bring it to given dimensions within the limits of .00001 of an inch. This is accomplished by drawing it through diamond burnishing dies many times, and reducing the dimension very minutely at each drawing. After being cut into approximate length for the spring desired, three to five pieces of wire, depending on the size, are wound around an arbor and inside of a ring in such a manner as to give each spring a perfect spiral shape, maintaining them uniform in length and all in a plane having the appearance of a flat piece of steel. In this condition the ring containing the springs i~ placed in a transferring tool, and here the springs are pushed out of the coiling ring and into the muffle. The muffle is a small cylinder and has the same diameter of hole as the coiling ring. Several layers of coiled springs are placed in each muffle, one layer upon another, until the muffle is nearly filled. The muffles containing the springs are now put through a heat treating operation to set the springs, so that when they are removed from the muffle the same size and shape will be retained that prevailed while in the muffle. After being removed from the muffle they are separated, and we can now notice the uniform space existing between the coils. This space is determined by the size of the wire used and the number of springs coiled together. Our next operation is to clean the springs as it is absolutely necessary to have them chemically clean before bluing. The bluing is done over an electric stove, the color being determined by the eye. We now have what is called a hairspring blank which must be tested for strength and inspected for shape and appearance before being accepted as ready for the finishing process.

The hairspring collet is made from brass rod, being blanked out on an automatic machine which shapes it, centers, drills and bores the hole; finishes the top, then cuts it from the rod. The diameter of the hole is a trifle smaller than the collet shoulder of the balance staff. The collet is now chucked in a lathe and the bottom surface countersunk. Next, the collets are placed in a loading machine where quite a number of them are strung on a piece of wire from which they are transferred to a magazine. This magazine is placed in a small machine where the collets are sawed, and this operation consists of slitting the side of the collet through to the center hole. The cbject of sawing the collet is to allow it to expand, and still maintain a firm grip when it is staked on to the collet shoulder of the balance staff. The hole for the hairspring is now drilled and countersunk and after the burrs have been removed by a tumbling operation, the collets are sent to the Gilding department where they are acidized and plated. When they are returned they are inspected for finish and accuracy and are now ready for attaching to the hairspring.

The pallet and fork blanks are first put through an operation to remove the burrs, then placed in a machine one at a time, where the center hole is drilled, countersunk, and burred. The next operation is that of punching the fork slit and hollow. Now we drill the dart hole and then we are ready to cut the slits for the pallet stones. This is a very particular operation as the size, angle, and position of the slits must be held to very close limits with respect to the center hole and fork slit. The center hole is now tapped in a small tapping machine. After the pallet is hardened and tempered, the fork slit is finished to the proper width, and the fork hollow ground so as to maintain the proper acting length of the fork. We now place several pallets in a special holder and grind the angle on the bottom of the fork at the fork slit. This operation is done to allow ample clearance for the fork as it passes between the table and safety rollers while the watch is running. A brushing operation is next in line for smoothing and polishing the fork slit and hollow, so as to minimize friction when in contact with the jewel pin. The pallets are now ready for the blocking and finishing operations where they are ground to the proper dimension, and the top surface polished.

After the pallet has been given a general inspection, the dart hole is reamed, and the tapered dart pin fitted tightly into the hole. The dart pin is now cut off flush with the dart stud on the side of the stud toward the center hole, and the opposite end left a trifle long so that it can be cut to length at a later stage of manufacture.

The dart pin is made on an automatic machine and is merely a tapered pin made from hard drawn nickel wire.

The pallet stone blanks are received in a rectangular form, and are considerable larger than necessary. They are blocked and ground on both of the sides and edges, which leaves the four planes of each stone perfectly flat and smooth.

The stone is now in the shape of a right rectangular prism. We now place these stones in a special machine where the impulse planes are ground and polished. The impulse plane has a convex surface, and the angle of the plane, with respect to the side of the stone, must be correct. Our next operation is to grind the stones to length, leaving just enough stock for the finishing. The grinding being done on the end of the stone opposite the impulse plane. The reason for having a convex surface on the impulse plane of the stone is to reduce friction when in contact with impulse plane of the escape wheel tooth.

The next operation is that of blocking, grinding and polishing the sides and edges of the stone, bringing it to the proper shape and dimension. The operation of finishing the corner, at the intersection of the impulse and locking planes, is done to remove any roughness occurring at this point. Finishing the length of the stones is accomplished by placing a quantity of them in a special holder, and grinding off the correct amount on the opposite end of the stone from the end having the impulse plane.

They are now inspected for finish, shape, and size.

The various grinding and polishing operations are done with laps charged with diamond powder. Several kinds of metals are used for these laps, also various grades of diamond powder with respect to fineness and cutting properties.

The diamond powder used for this purpose is received from the Gilding department and graded in the Escape department.

The escape wheel blanks are made in the Spring department, and when received, the center, arms, and rim of the wheel are finished and ready for cutting the teeth. Our first operation is the blocking and surfacing of both sides of the blank, then after being cleaned and inspected, a number of blanks are placed on an arbor of a special machine and the teeth are cut. All dimensions and angles of the escape wheel tooth must be held to very close limits. The wheels are again blocked and the top side of the wheel polished. The impulse plane of the tooth is also highly finished.

The double roller blank is received from the Screw department and is made to very close dimensions. The first operation on the double roller is to block up and grind both top and bottom surfaces so as to remove all burrs from the blanks. Then the center hole is reamed to correct diameter and the roller placed on a true rotating arbor and tested for concentricity. After passing this test the passing hollow, or crescent, is milled in the safety roller. The rollers are now sent to the Spring department where the hole for the jewelpin is punched in the table roller. After being returned from the Spring department, they are hardened, being left hard at this stage. We now tumble them so as to remove all loose burrs, then finish the periphery of the safety roller leaving it with a smooth highly glossed finish.

Next, we put them through a brushing operation which cleans up all parts of the blank. The last operation consists of blocking, grinding, and finishing both ends. The correct thickness of both rollers, and the over all dimension must be maintained. They are now sent to the heat treating department and the temper drawn. Our last operation is to cement the jewelpin into the table roller. The pin must be upright and the flat face of the pin set so as to be perpendicular to the line of centers between the center hole and the jewelpin hole.

The balance staff blank is made in the Train department and when received is completely finished with the exception of the pivots. Our first operation is to place these blanks in a jigging block, grind and polish both ends, and maintain the correct dimension to each end from that part of the staff known as the balance seat. We now grind and polish the conical pivots to size, after which the ends are finished. All balance staffs are run to indicate the concentricity of the roller and balance shoulders before being sent to the inspection job where the size, shape and finish of all pivots are very closely inspected.

The balance is made in the Spring department and our first operation is to stake the balance staff to it, being certain that the staff is tight in the balance.

We now place the number on the lower surface of the balance arm using a diamond point for this purpose. The number corresponds to that of the movement in which the balance is to be used. The double roller is now fitted to the staff so that when driven down to place it will remain firmly in the proper position. The assembly is now inspected by being placed in a caliper with open jewels so that when the balance is rotated the condition of the pivots can be observed, as well as the truth of the double roller. The jewel-pin is also inspected at this time to be certain that it is firmly cemented in the table roller. The balance is now ready for sawing, and this operation is done on a semi-automatic machine. Two slits are sawed through the rim exactly opposite and close to the balance arm. The sawing of the rim at these two points is necessary to allow the balance to function in compensation.

The truing of the balance is done in a caliper in which the balance can be rotated on its axis, and by the use of an index, the balance truer can determine where the balance rim is out of true, and by bending the rim and the arm where necessary, the errors are corrected. When a balance is true all corresponding points on the rim of the balance must be equidistant from the center and lying in a plane which is perpendicular to the axis of the balance staff. The balance is now cleaned before poising. In poising, the balance is placed on two straight parallel ruby jaws, the edges lying in a plane which is perfectly level. The space between the jaws is so adjusted as to allow the cylindrical part of the pivots to rest on the jaws. It is understood that the edges of the ruby jaws supporting the balance pivots have a microscopic radius, thus reducing friction to a minimum. It is now obvious that the heavy portion of the balance will settle at the bottom, consequently weight must be removed from the heavy part until the balance will stand in any position. The balance screws are used for poising and also for timing. In reducing the weight of the balance at a certain point, a screw nearest this point is placed in a chuck, and removed from the balance. Now while the screw is being rotated a special cutter is brought against the bottom of the head, removing weight by undercutting. This does not change the appearance or length of the screw. Several screws are usually undercut in poising a balance. After being poised the balances go to the final inspecting job where they are given a general inspection for truth, condition of pivots, loose or damaged screws, and appearance. Now they are thoroughly cleaned and then inspected for poise. When they are passed by the poise inspector and checked for proper location in the trays, they are ready to be delivered.

In finishing the hairspring the first operation is that of attaching the collet and stud to the spring. In this operation the collet and stud are placed in a special tool, and the inner end of the spring inserted into the spring hole of the collet.

A tapered hard brass pin is now forced tightly into the hole and both ends of the pin broken off flush with the collet.

The outer end of the spring is now fastened to the stud in a similar manner.

It is very important that the spring be securely fastened in both instances. Our next operation is to form the overcoil, then raise and level the same. Both of these operations are intricate and must be thorough. The main object of the overcoil is to bring the center of gravity of the spring at the axis, or as near the axis as possible.

In truing the hair-spring the collet is staked on to the collet seat of the truing arbor.

This truing arbor is pivoted in the same manner as a balance staff, having the colletseat absolutely true with respect to the pivots. A dummy balance is pressed on so that it can be rotated or spun with the finger, the inertia of the balance serving to keep the assembly in motion. By placing this assembly in a caliper, and rotating it, the hairspring truer can now observe the errors and correct them by manipulating the first quarter coil of the spring nearest the collet.

A special fine pointed tweezer is used for this purpose. When the hairspring is true the center of the spiral is at the axis of the arbor, and the plane of the spring is perpendicular to the axis of the arbor. After being inspected for truth, and general appearance the springs are removed from the arbors and placed in bakelite trays, each of which contains 100 springs and each spring is kept separate.

In the process of completing the escapement our first operation is that of fitting the escape pinion into the escape wheel, and pressing the wheel to the correct position on the shank of the escape pinion. The escape pinion is made by the Train department. The assembly is now placed in a tool which supports the pinion between centers, and the wheel is rotated. An indicator is used for determining the concentricity of the wheel with respect to the axis of the escape pinion. In the next operation the pinion is again supported between centers in a tool which has an indicator for testing the truth of the wheel in the flat.

The wheel is now rotated and Dy observing the indicator, the operator can determine where the error exists, and, if necessary, correct it by bending or springing the wheel to proper position.

In completing the pallet, the pallet arbor is screwed into the pallet and fork so that the shoulder on the arbor is brought tightly against the lower surface of the pallet. Now this assembly is placed in a tool to test the pallet for upright, or in other words, to observe that the top surface of the pallet is perpendicular to the axis of the arbor.

The next operation is that of cutting off and angling the dart pin, maintaining the proper length from the axis of the pallet arbor. The pallet is now placed in a small tool and the receiving and letoff stones securely cemented into their respective slits. It is very important that the impulse planes of both stones are placed in the proper position with respect to the axis of the pallet and the center of the jewelpin slit.

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