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The Encyclopedia of Horology

Component record · Plates & finishing

Main Plate

Partially verified

The principal plate to which all other movement parts are located.

What it does

Provides the datum for every bearing, bridge and dial-side mechanism.

How it works

Every hole, recess and seating is machined relative to the plate, so plate distortion affects the whole movement.

Calibre identification usually begins from plate architecture and markings.

Evolution

Machining accuracy improved with industrial production, enabling true interchangeability.

Known variations

  • Full plate
  • Three-quarter plate
  • Bridge calibre

Identification for collectors

  • Plate markings, shape and jewel layout identify a calibre more reliably than a dial signature.

Common failure modes

  • Distortion from over-tightened clamps
  • Worn unjewelled holes

Diagram

top plate or bridgespillar platebalance and cockwheel train between the plates
Schematic: plate and bridge layout. An outline schematic drawn to show the arrangement of the parts discussed here. It is not a dimensioned working drawing and does not depict a particular maker's calibre.

Sources & references

  1. de Carle, D., Practical Watch Repairing
  2. de Carle, D., Watch and Clock Encyclopedia
  3. Daniels, G., Watchmaking

Where sources disagree, the disagreement is stated rather than resolved silently.