Monday, May 25, 2009

Hamilton 987 movement revealed

Modern movements are mostly mass-produced - in fact, it has been said that some are untouched by human hand.  While the technology and the use of exotic materials has progressed indeed, there is something enduring about a movement made the "old-fashioned" way.  In the first half of the 20th century, Hamilton was in the forefront of American watch manufacture.  This 987 movement was made at the very beginning of the Great Depression.  Although it is a production-line movement, it does show considerable attention to detail.  The size is 6/0 which makes it just about 1" diameter (see a good explanation here).

body dialside
The dial side of the body is decorated with pearlage, done by hand.  The serial number 4092105 dates the movement to 1929 or 1930.  There are three holes for the dial posts as opposed to only two on later movements.  The cross-headed brass heads are for adjusting the lever banking pins.  The balance pivot cap jewel can be seen just below, held by two tiny countersunk screws - later movements use just one.  On the minus side, there is an off-center staking on the pallet pivot jewel and the balance pivot cap seems to have taken a hit :-(

body topside
The top side is also decorated with pearlage.  The banking pins are eccentric which allows the banking to be adjusted merely by turning the screws - instead of the tedious shaving or staking used on modern watches where the banking is formed as an integral part of the pallet bridge.  Other watches have bendable posts which can snap and, when bent, become out-of-square with the pallet lever unless you do it correctly which is really, really difficult.

Here we see the côtes de geneve decoration on the bridges.  The machining on the two wheels is beautifully done with beveling and undercutting plus that nice helical effect.  Not sure of the correct term but it's done by scribing from the center radially outward while the wheel is turned at constant speed.  The jewels are held in chatons, including the center-wheel jewel which is quite unusual.  The engraving was filled with black enamel originally, most of it gone now.

keyless works
The keyless work is simplicity itself and shows it's pocket watch origins - no pesky wire springs or pressed tin here!!  The minute wheel shows little sign of wear for a 80-year old watch.

pallet lever bridge
The pallet lever bridge is shaped symmetrically and the stamped numbers match the serial number marked on the movement body.  These movements are from an era when parts were tweaked to fit together during manufacture, as opposed to being assembled from fully interchangeable parts.  Hence the need to match numbers in a similar way to other machinery such as handguns or rifles where "matched numbers" are de rigeur.

pallet lever
Sorry about the poor shot of the pallet lever.  The lever is pretty plain compared to the rest of the movement - no beveling, for example.  The shaft appears to be bent but it will be left as-is.  It is so easy to "repair" a perceived problem only to find that the movement stops working!  So, unless escapement mis-locking occurs, it will be left alone.

balance and cock
The balance cock is held firmly in place with three posts as opposed to the more modern two.  The hairspring is of blued spring steel and, as such, is affected by temperature.  This is offset to an extent by the temperature-compensated bi-metallic balance rim.  The rim also has four timing adjustment screws; there is a small scratch on one of the arms where someone slipped while making an adjustment.  Matching numbers, of course ;-)

Best regards,


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