How balance staffs
are replaced
Ken Pell
Components of balance
assembly
•
•
•
•
Wheel (split or solid)
Staff (riveted or friction)
Hairspring (flat or overcoil)
Roller (single or double)
Balance wheel
Roller
Hairspring
Wheel
Staff
Roller a
Jewel
Roller Hub
Pivot
Hairspring Hub
Wheel Hub
Why they must be replaced
• Trauma, such as dropping or bumping
watch which damages the staff and jewels
Broken Pivot
Pre staffing
• Clean movement
• Examine and replace balance jewels
• Identify movement early and secure new
staff
Good Hole Jewel
Cracked
Hole Jewel
Chipped
hole jewel
Selecting replacement staff
•
•
•
•
Determine grade of watch
Use Elgin reference for staff number
Order staff
Verify measurements
Make a new staff?
• Not necessary 99% of time
• Need expertise on lathe
• Outsourcing is possible
Take measurements
• Hairspring hub
• Roller hub
• Pivots
Compare old to new
Pivot
Hairspring
Wheel
Roller
Old staff
New Staff
Modify if needed
• Reduce diameter of hubs using lathe.
• Choose another staff
Steps
• Remove hairspring
• Remove roller
• Remove balance wheel
Mark the postion of the stud
Mark
Position
Of collet
Mark position
Of roller jewel
Remove wheel from staff
• Place staff in hole of table with wheel
resting on the table.
• Push or tap staff out
Wheel is resting
On table
Restaffing
• Place staff with roller side down in staking
set.
• Choose appropriate round face and flat
face punches.
• Place wheel over staff
• Rivet
Rivet
• Use round face first, then flat
• Turn punch while tapping
• Always use brass hammer
• Test In lathe
Replace roller
• Place on punch with hairspring side down
• “Three quarter” test
• Make sure jewel clears punch
• Tap or press on
Roller sits
3/4th down