GRAM

Definition

The gram (symbol g) is the usual unit of mass in watchmaking, equal to one thousandth of a kilogram. Component masses are often well below a gram, but it remains the common reference for characterizing certain parts and operations.

Uses in watchmaking

The gram is used to quantify the mass of parts such as the watch case, the bracelet/strap, or the oscillating weight (rotor) of an automatic movement. A difference of a few tenths of a gram in the oscillating weight can noticeably alter the winding autonomy.

Precision and tolerances

For regulating components, mass tolerances are much finer and are expressed more in milligrams: an uneven distribution of mass on the balance directly affects its inertia, and therefore the timekeeping.

Precious materials

The gram is also used in dosing precious materials, gold or platinum, when manufacturing cases or plated components, where the weight determines the amount of metal used and its value.

Good to know

In workshops, precision scales graduated to the centigram, or even the milligram, are used to check these masses throughout manufacturing and regulation.