AS1250 (A Schild) bumper movement service – Perfex Gold plated

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I bought this one ebay as a semi non runner, the type that runs for a few seconds then stops. Normally this could denote a few things, but a service is a great place to start. A Watch is an intricate little machine with pivots and jewels, but over time the oils and greases attract dirt, go old and get sticky.


The main reason for purchasing was that I really wanted to try a 1940’s or 1950’s bumper automatic. Modern automatics have a rotor that spins, the early bumpers swing one way, hit a spring, and return back until they hit another spring, and so on. When your wearing one you can feel this action and it’s pretty cool.

For the service the watch was stripped to its individual components, the main spring replaced, the jewels were first polished with sharpened peg wood to remove as much grime as possible.

The parts are then washed in a rotary cleaning machine, and then double rinsed before being dried.

Rebuilding with the correct oils and greases is a standard, the video shows the rebuilt movement being tested for speed, amplitude and beat error. The video shows a slight beat error that needed correcting.

Beat error is the time between tick and tock, the swing of the balance wheel as the jewel hits the pallet to release the escape. In a perfect world the time back and forth is equal. Beat error is when there is a difference in the swing duration – tick and tock are not the same.

A lovely watch at the end of the day and a real glimpse into the history of watch movements – every collection should have a bumper in it

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