Introduction
Worn pivot holes are one of the most common causes of power loss in mechanical clocks. When a pivot hole becomes oval or enlarged, the arbor leans, the gears mesh poorly, and the movement loses efficiency. Bushing work restores proper pivot support and gear alignment. This guide explains how to diagnose wear, how to center a bushing accurately, and how to test the movement after installation.
How to Identify When a Bushing Is Needed
Visible oval wear
If the pivot hole is elongated, the arbor will shift under load.
Arbor lean
When the arbor tilts noticeably, the gears mesh too deeply or too shallowly.
Endshake changes under pressure
Pressing lightly on the wheel may cause the arbor to bind or shift.
Power loss symptoms
Weak pendulum swing, stalling, or inconsistent running often indicate worn bushings.
Escape‑train sensitivity
Wear in the upper train causes fluttering, skipping, or erratic escapement action.
Preparing for Bushing Work
Let down all power
Fully release mainspring tension before removing the plates or working on the movement.
Disassemble the movement
Remove the plates carefully and keep wheels organized by train.
Inspect pivots
Polish pivots before installing new bushings—clean pivots ensure accurate fit.
Mark the original pivot center
Use a sharp scribe or centering tool to preserve the correct pivot location.
Choose the correct bushing size
Select a bushing that fits the pivot snugly without excessive clearance.
How to Install a Bushing
Step 1: Center the worn hole
Use a centering tool or depthing reference to ensure the new bushing aligns with the original pivot location.
Step 2: Ream the plate
Remove only enough material to accept the new bushing—avoid enlarging the hole excessively.
Step 3: Press in the bushing
Install the bushing flush with the plate, ensuring it seats firmly.
Step 4: Broach the inside diameter
Open the bushing gradually until the pivot spins freely with minimal play.
Step 5: Test the arbor
Verify smooth rotation and proper endshake before reassembling the movement.
Troubleshooting Flowcharts
If the arbor binds after bushing
Hole off‑center → Bushing too tight → Pivot rough → Plate not flat
If the train runs stiffly
Check depthing → Check pivot polish → Check bushing alignment → Check wheel mesh
If the escape train misbehaves
Check upper‑train bushings → Check pivot wear → Check escapement alignment
If the movement loses power
Check for tight bushings → Check pivot cleanliness → Check plate distortion
If the clock stops intermittently
Check endshake → Check arbor lean → Check bushing size → Check pivot burrs
Common Mistakes to Avoid
Over‑broaching the bushing
Too much clearance causes lean and power loss.
Off‑center installation
Misaligned bushings cause depthing errors and binding.
Skipping pivot polishing
Dirty or rough pivots wear new bushings prematurely.
Pressing bushings too deep
Sunken bushings alter endshake and cause binding.
Testing without full assembly
Always test the train under partial power after reassembly.
Checklist for Final Verification
• Bushings centered
• Pivots polished
• Arbors spin freely
• Endshake correct
• Train runs smoothly
• Escapement stable
• Movement runs full duration
FAQs
How do I know if a bushing is needed?
Visible wear, arbor lean, or power loss are strong indicators.
Should I oil the new bushing?
Yes—apply a tiny amount of proper clock oil to each pivot hole.
What if the bushing is slightly off‑center?
Even small errors can cause binding—re‑center if necessary.
Do all worn holes need bushings?
Only holes with measurable wear or functional issues require replacement.
Is bushing work beginner‑friendly?
Yes, with patience, proper tools, and careful centering.
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