· By Buffy
Friction and Lubrication
Oil is the watchmaker's real craft: which bearings get which drops, why epilame exists, and how friction becomes rate.
A mechanical watch runs on roughly a microwatt of power. Friction is not a nuisance in such a machine; it is the environment. Everything about servicing — cleaning, oils, epilame, timing — is friction management.
The friction budget
Power leaks at every pivot, every tooth mesh, and above all at the escapement impulse surfaces. Because the amplitude directly reflects the energy balance, friction shows up there first and as rate drift second (a loaded balance oscillates slightly slower in practice — positional and isochronism effects compound).
The oil schedule
Watch oils are engineered fluids with specific viscosities and temperature behavior. The classic bench logic:
| Site | Oil | Why |
|---|---|---|
| escape & pallet pivots | light (e.g. Moebius 9010) | fast, low torque |
| balance staff | lightest + capstone jewels | speed of oscillation |
| train pivots, cannon pinion | medium (HP-1300 class) | load × speed |
| barrel arbor, winding | heavy / grease | slow, high load |
| barrel wall (mainspring) | braking grease | controlled slip of the bridle |
| chrono coupling, keyless | grease (8200 class) | impact and sliding |
Too light and it drains away; too heavy and amplitude dies. Aging oil oxidizes and thickens — the mechanism of “it ran fine until it didn’t.”
Epilame and surface treatment
Epilame (e.g. Fixodrop) is a surface treatment that holds oil in place by surface tension control. The escapement impulse surfaces are epilamed so the microscopic oil drop stays on the impulse plane instead of creeping across the stones. Surface engineering in the 1930s–50s made modern service intervals possible; the co-axial is, philosophically, an attempt to make this whole page less important.
Shock settings
Balance jewels sit in shock settings — spring-mounted jewel cups (Incabloc from 1934, KIF, Paraflex, Diashock and others) that let the jewel move a hair under impact and snap back. They protect the pivots, not the jewels; their springs take a set over decades. A watch with a broken shock spring shows up at the bench with a snapped staff — the classic dropped-watch autopsy. See The Balance Assembly.
What owners should know
- Servicing is mostly cleaning and re-oiling; wear parts come second. The 4–7 year interval is an oil life estimate, not superstition.
- “Magnetized” watches (here) act like lubrication failures but cost nothing to fix.
- A watch that runs 30 s/day slow after years of use is usually friction’s long argument, not a broken escapement.
- Never lubricate anything at home. Ever.