Introduction
Arbors and pivots are critical components in every mechanical clock movement. Worn or damaged arbors cause depthing issues, power loss, and premature wear on gears and bushings. This guide explains how to choose the correct arbors and pivot hardware for your clock.
Understanding What Arbors & Pivots Do
Support gears and pinions
Arbors hold gears and pinions in place and allow them to rotate smoothly.
Maintain proper depthing
Correct arbor length and pivot diameter ensure gears mesh at the correct distance.
Transfer power through the train
Pivots must be smooth and properly sized to minimize friction and wear.
How to Measure an Arbor Correctly
Measure total arbor length
Length must match the plate spacing exactly to avoid binding or excess play.
Measure pivot diameter
Pivot diameter determines the correct bushing ID and affects friction.
Measure shoulder placement
Shoulders determine gear spacing. Incorrect placement causes depthing issues.
Choosing the Correct Pivot Hardware
Match pivot diameter to the bushing
Pivots must fit the bushing ID with minimal clearance.
Match pivot length to the plate thickness
Pivots that are too short cause wobble; too long cause binding.
Check pivot hardness
Hardened steel pivots last longer and reduce wear on bushings.
Matching Arbors to the Movement
Identify the movement manufacturer
Hermle, Urgos, and Kieninger use different arbor lengths and pivot sizes.
Match the gear and pinion configuration
Arbors must match the original gear and pinion layout exactly.
Check for bent or worn arbors
Even slight bends cause binding and poor power transfer.
Common Arbor & Pivot Materials
Hardened steel pivots
Most common. Provide excellent wear resistance.
Brass arbors
Used in some antique clocks. Softer and require careful handling.
Repivoted arbors
Used when original pivots are worn. Must match original dimensions.
Common Mistakes When Choosing Arbors & Pivots
Guessing pivot diameter
Incorrect pivot size leads to poor bushing fit and excess friction.
Ignoring shoulder placement
Incorrect spacing causes gears to mesh improperly.
Replacing only one worn component
Worn gears, pinions, or bushings may also need replacement.
Recommended Internal Links
FAQs
How do I know what arbor my clock needs?
Measure the total length, pivot diameter, and shoulder placement of the original arbor.
Can I replace a pivot without replacing the arbor?
Yes, but the new pivot must match the original diameter and hardness.
Why does my arbor bind when installed?
The arbor may be bent, too long, or incorrectly spaced at the shoulders.
Do all clocks use the same pivot sizes?
No. Pivot sizes vary widely by manufacturer and movement type.
Should I polish pivots before reassembly?
Yes. Polished pivots reduce friction and extend movement life.
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