Repairing a Hamilton 4992B

Published: June 9, 2014
This front view shows a running Hamilton 4992B after a crystal replacement.

This front view shows a running Hamilton 4992B after a crystal replacement and service job.

This Hamilton 4992B came into our shop without a crown. It was also running intermittently. It was fairly dirty, which can make any watch run intermittently. In addition to being dirty, this watch needed a new balance staff to run well. These things were both spotted prior to disassembling the watch.

We completely disassemble each pocket watch when we perform a service and inspect each part. In doing so to this watch, we found that the sweep wheel (which drives the sweep second hand) was out of true – it wasn’t flat. We trued the sweep wheel, not because it was causing a problem, but because it wasn’t the way it was when it came from the factory.

There are a few differences between 4992B and 992B pocket watches. I won’t go into them all (mainly because if I claim to cover them all I will forget one).

The most noticeable difference is the second hand. On 992B watches, the second hand is attached to the 4th wheel and is found at the six o’clock position on the dial. In other words, it is at the same spot it is on nearly every other pocket watch made until this watch was released. Directly related to this is the hack mechanism. 992B pocket watches will continue to run when the crown is pulled into the setting position even though they will run a little slower in this position due to the watch also driving the setting position. On a 4992B, pulling the crown out sends a small wire into contact with the balance wheel, stopping the watch. This allowed military personnel using the 4992B to synchronize their watches down to the second. Most military personnel using the 4992B were in a position requiring precise timekeeping for navigational purposes.

The 4992B has one more jewel than the 992B does. This extra jewel is to reduce the friction caused by the sweep hand pinion.

The final difference we will discuss is that 4992B watches are 24 hour watches. The hour hand thus only rotates once a day, where on a 992B and other 12 hour watches the hour hand would make 2 full revolutions in a day.

This is a Hamilton 4992B movement after being serviced and cased.

This is a Hamilton 4992B movement after being serviced and cased.

This watch’s case was very brassed so we elected to not polish the case – doing so would have damaged it. A brassed case is simply a case in which the outermost material, in this case chrome, has worn away and revealed the case’s inner material.

This 4992B is now running well and has been keeping excellent time. We’ll send it back to the customer after we test it for a few more days.

“Do you want me to send the flack box with the watch?” the customer asked. Thinking about shipping weight only, I foolishly replied, “No.” Now, a few days after the 70th Anniversary D-Day settings, I really regret my answer.

You see, a generation of young men flew, sailed, and drove into combat with 4992B’s guiding and timing them. I’d love to see this watch in its flak box. It runs well on my desk, but that isn’t where it was made to run. It was made to run in a bomber that was straining to deliver a payload and to return a crew to base.

Hugh C. Weaver wrote in “WWII Bomber Pilot’s Poem:”

First it puffed, and then it bellowed, like a clashing cannonade
Belching ragged steel which ripped and then destroyed;
Tough metal twisted, engines coughed, heavies fought and then they swayed
‘Til they finally hit the rally and deployed.