Watch Oil

Specification

Technical parameters

Overview

Watch oil exists to keep a metal pivot from wearing against its jewel. It is not a general-purpose lubricant: different viscosities are specified for different loads and speeds, and the choice is governed by how much torque a bearing sees and how fast it moves.

A typical service uses two or three viscosities. A light oil for the fast, lightly loaded bearings of the escapement and train; a medium oil for the slower, more heavily loaded wheels; and something considerably heavier for the barrel, which is really grease territory. Using one oil everywhere is a compromise that shortens service intervals.

Quantity is where most amateur work goes wrong. The bearing is a jewel hole with a small oil sink around it, and the correct amount is a film that partly fills that sink — not a drop. Excess oil migrates by capillary action, starves the bearing it was meant for, and eventually reaches the hairspring, where it destroys the rate.

What matters about it

• Viscosity matched to bearing load and speed
• Formulated to resist migration and drying
• Applied as a partial fill of the oil sink
• Different grades for train, escapement and barrel
• Degrades with age even unopened

Practical notes

• Oil the sink, not the hole — the capillary gap does the rest.
• Cap the bottle the moment you finish; exposure thickens oil measurably in weeks.
• Never oil pallet impulse faces, the hairspring, or the balance rim.
• Label each bottle with the date opened and replace it on schedule.

Compatible with