Introduction
Clock gears and pinions transfer power through the movement, controlling timing, strike, and chime functions. Choosing the wrong module size, tooth count, or arbor fit leads to binding, excessive wear, or a clock that won’t run at all. This guide explains how to choose the correct gears and pinions for your mechanical clock.
Understanding Gears and Pinions
Gears transfer rotational power
Larger gears reduce speed and increase torque.
Pinions receive power from gears
Pinions typically have fewer leaves and rotate faster.
Both must match the movement’s module
Module determines tooth size and spacing.
How to Identify the Correct Gear or Pinion
Measure the module size
Module is the most important measurement. Incorrect module causes binding or skipping.
Count the teeth or leaves
Tooth count determines gear ratio and timing accuracy.
Measure the arbor diameter
The gear or pinion must fit the arbor without wobble or excessive friction.
Matching Gears and Pinions to the Movement
Identify the movement manufacturer
Hermle, Urgos, and Kieninger use specific module sizes and tooth profiles.
Match the gear train function
Time, strike, and chime trains use different gear ratios and pinion sizes.
Check the pivot length and shoulder height
Incorrect pivot length causes binding or plate misalignment.
Common Gear and Pinion Materials
Brass gears
Most common and ideal for smooth, long-term operation.
Steel pinions
Used for durability and high-speed rotation.
Alloy gears
Modern option for lightweight, low-friction performance.
Common Mistakes When Choosing Gears and Pinions
Mixing module sizes
Even a small mismatch causes skipping or binding.
Incorrect tooth count
Alters gear ratios and disrupts timing.
Wrong arbor diameter
Too loose causes wobble; too tight causes friction and wear.
Recommended Internal Links
- How to Choose the Correct Clock Mainsprings
- How to Choose the Correct Clock Bushings
- How to Choose the Right Clock Arbors
- How to Test a Clock Train During Reassembly
FAQs
How do I measure module size?
Module is calculated from tooth spacing. Use a module gauge or match the original gear.
Can I change the tooth count to adjust timing?
No. Tooth count must match the original design to maintain correct ratios.
Do gears and pinions from different brands interchange?
Only if the module, arbor size, and tooth count match exactly.
Why does my replacement gear bind?
Likely a module mismatch, incorrect pivot length, or improper arbor fit.
Can I mix brass gears with steel pinions?
Yes. This is standard in most mechanical clock movements.
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