|Three typical Watch bushes.|
Occasionally there will be some wear to the pivot as well in which case the pivot will need to be smoothed and reduced in size which will result in it being loose in the hole.
Problems are most common on the fast moving and quite small 4th (Seconds) wheel and on the bottom pivot of the centre wheel which although it moves slowly it has a lot of pressure on it and can't be effectively oiled without taking the movement apart - so it seldom gets done.
To remedy this situation a brass Bush or "Bouchon" is set into the movement.
The bush has to be a friction fit but not so tight that excessive force is required to push it in or the bush could be damaged or the movement distorted.
|The reamer on the centre hole of a scrapped bottom plate. The metal is soft and the |
tool very sharp so it is just turned by hand with no significant leverage required.
|My staking set with leaver operation, a different anvil than this would |
probably be used when pressing home a bush.
The result will be as efficient as the original.
A re-bushed centre wheel pivot hole that I did recently.
Although more expensive, sometimes a jewel will be used instead of a bush resulting in a higher jewel count than advertised:
|This Waltham Traveler has been turned into a 15 jewel watch although I suspect |
that was because someone wanted to do it rather than to correct a problem.
Bushes used to replace jewels at the 4th wheel and below will not be as efficient as a jewel and will be more prone to wear in the very long term.