Introduction
Bushings restore worn pivot holes and are essential for proper movement performance. Choosing the wrong bushing size, style, or thickness leads to poor depthing, excess friction, or premature wear. This guide explains how to choose the correct clock bushings for your mechanical clock.
Understanding What Bushings Do
Restore worn pivot holes
Worn holes cause depthing issues, power loss, and erratic running.
Provide a smooth bearing surface
Properly sized bushings reduce friction and extend movement life.
Maintain correct gear alignment
Incorrect bushing size or placement causes binding or skipping.
How to Measure for the Correct Bushing
Measure the pivot diameter
The bushing’s inside diameter (ID) must match the pivot size with minimal clearance.
Measure the worn hole’s outer diameter
The bushing’s outer diameter (OD) must fit securely in the plate after reaming.
Check the plate thickness
Choose a bushing with a thickness that matches or slightly exceeds the plate.
Choosing the Correct Bushing Style
Press-in bushings
Most common. Installed after reaming the plate to the correct OD.
KWM bushings
Use a standardized OD system. Ideal for German and American clocks.
Butterfly or screw-in bushings
Used on some antique clocks. Require matching thread or wing style.
Matching Bushings to the Movement
Identify the movement manufacturer
Hermle, Urgos, and Kieninger plates vary in thickness and pivot sizes.
Match the pivot material
Hardened steel pivots require precise ID sizing for proper lubrication.
Check for tapered or worn pivots
Polish or repivot before sizing the bushing to avoid misalignment.
Common Bushing Materials
Brass bushings
Most common. Provide excellent wear resistance.
Bronze bushings
Used for high-load pivots. More durable but harder to install.
Oversized bushings
Used when the plate hole is severely worn or enlarged.
Common Mistakes When Choosing Bushings
Choosing by visual similarity
Bushings that look similar may differ in ID, OD, or thickness.
Ignoring plate thickness
Thin bushings cause side-shift; thick bushings cause binding.
Failing to polish pivots first
Dirty or tapered pivots lead to incorrect ID sizing.
Recommended Internal Links
FAQs
How do I know what size bushing I need?
Measure the pivot diameter for the ID and ream the plate to match the bushing OD.
Can I use a bushing that is slightly oversized?
Only if the plate hole is severely worn. Otherwise, use the correct OD.
Do all clocks use the same bushing system?
No. KWM and Bergeon systems use different OD standards.
Why does my clock bind after installing a bushing?
The bushing may be off-center or incorrectly sized.
Should I oil the bushing after installation?
Yes. Use a small amount of clock oil on the pivot after assembly.
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