The watch movements have some bearing jewels.
The main reasons are for:

• To move wheels smoothly without friction and transmit power efficiently.
• To prevent wear of wheel’s pivots.

If a hole jewel has chip or crack, the pivot will make damage.

The jewel has chip around the hole.

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The chipped jewel has been taken out.

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Reaming the hole for a replacement hole jewel.
The most important thing for the job is keep the center.

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The new hole jewel has been replaced.

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Completed!