OVWCCC MasterClass - The Art of Bushing
Session will be mentored by John Deland and Paul Sonnichsen
The art of bushing a clock is a classic skill in clock repair and horology. It refers to installing small metal bushings into worn pivot holes in a clock plate to restore proper gear alignment and reduce friction. Over many years, the steel pivots of the clock’s gears wear the softer brass plates, enlarging the holes and causing the clock to lose power or stop.
Clockmakers “bush” the holes to bring them back to the correct size and position.
Why clocks need bushing
Inside a mechanical clock:
- Gear shafts (called arbors) rotate on pointed ends called pivots.
- These pivots run in holes in the brass clock plates.
- After decades, the holes become oval-shaped due to wear.
This causes:
- gears to mesh incorrectly
- increased friction
- poor timekeeping or the clock stopping
Bushing restores the hole to the correct size and alignment.
The basic bushing process
1. Identify worn pivot holes
The clockmaker checks for:
Special magnification or pivot gauges are often used.
2. Ream the worn hole
A clock reamer enlarges the worn hole into a perfectly round hole.
Purpose:
- remove uneven wear
- prepare the hole for a bushing
Accuracy here is critical so the gear stays in the exact original center position.
3. Install a brass bushing
A small pre-made brass bushing is pressed into the reamed hole.
Bushings are tiny brass sleeves with a hole in the center.
Clockmakers choose the correct:
- outer diameter
- inner diameter
4. Broach the pivot hole
The center hole in the bushing is adjusted with a broach (a tapered cutting tool).
Goal:
- make the hole perfectly sized for the pivot
- ensure the arbor spins freely with minimal play.
5. Trim and finish
The bushing is:
Then the clock is reassembled and tested.
Tools commonly used ️
Clock bushing work uses specialized tools:
- Bushing machine (e.g., Bergeon or KWM)
- Clock reamers
- Broaches
- Pivot gauges
- Brass bushings
- Depthing tool (checks gear alignment)
Why it’s considered an “art”
Although the process sounds mechanical, it requires:
- extremely precise alignment
- knowledge of gear depthing
- careful tool control
- experience judging wear patterns
A poorly placed bushing can cause:
- binding gears
- loss of power
- inaccurate timekeeping.
A good clockmaker can bush a clock so precisely that the repair lasts another 50–100 years.
Pre-requisites: Registrants must bring
- a mag visor
- a disassembled striking clock movement (preferably American), without mainsprings
- cutting and smoothing broaches
- small files
- sharp scriber
- fine tip marker
This member only event is limited to 12 students + 2 instructors.
Registration opens March 10, 2026
Please contact us if you are a member and are experiencing difficulty with registration.
Not a member and wish to attend?
Please join the club here , before registering for the workshop
The November Club meeting will take place after the workshop, at 1:00pm
Using Electronic Tools in Horology
With the advancement in electronic tools, monitoring the timing and performance of mechanical timekeepers has risen to a new standard.
We are excited to host a workshop demonstrating these amazing devices for aaperformance and The wristwatch basic intro workshop is for beginners interested in learning to work and service their own wristwatches, manual winding or quartz.