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The original pivot on the rear of this
Longcase Center Wheel has been worn to a bulb shape. In a very short time the neck would have broken and the wheel would have been free to revolve at high speed, seize with other wheels, break teeth and wreck the hands. The damaged pivot is cut off and the surface stoned flat. |
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Next the wheel is set in the lathe using a
steady as the pinion is very long. Using a Tungsten Carbide bit a hole is drilled SLOWLY to about 6mm and dead center to the pinion. In order to achieve a central hole it is helpful to use the centerng tool described by Mr J M Huckabee CMC FBHI FAWI of the American Watchmakers Institute. This is home-made and consists of a brass tube where the internal hole is just the size of a Tungsten Carbide bit and of a length that allows the tip to protrude yet leaving sufficient of the shank to be held in the fingers. The tip end is drilled to an internal cone. When this cone is placed over the stump of a pinion and the drill bit gently but firmly applied through the body of the tool it must happen that the pilot mark will be central. |
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When the hole is about 6mm deep (I like to
make it at least two to three times the Plate thickness) change the bit for one
slightly larger and then larger still up to the size of the prepared pivot
steel. Use plenty of oil and a slow speed. Remember always that in antique pinions one can encounter some extremely hard spots that tend to break bits. It is for this reason that TC bits are used. If the bit should break in the hole it can be broken up using thin pivot steel and sharp taps from a clock hammer. If a HSS bit breaks it cannot be fragmented and might prove difficult to remove. Next wash everything in de-greasing fluid and allow to dry. Place a drop of Stud-Lock in the hole and insert the new pivot. Tap into the root of the hole and allow to set for at least one hour. Set up in the lathe and polish the new pivot. |
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DISCLAIMER Please understand that the balance, its spring, the pallets, the escape wheel and all associated mechanisms are delicate and are best serviced by an experienced horologist who could well be a member of the British Watch and Clock Makers' Guild or the American Watchmaker Institute. The author can accept neither responsibility nor liability for any loss or damage howsoever caused by any person carrying out adjustments to either their own property or that of any other person. These notes are given in good faith and must not be considered to be a definitive exposition of the subject.
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