SNAP (BARREL NOTCH)

The Snap (barrel notch) is the notch, the circular recess machined on the inside of the Barrel drum, intended to receive and hold the cover of the Barrel. The Barrel is the cylindrical housing that holds the mainspring; it consists of the drum (the body), the cover, and the Arbor. To close the barrel, the cover snaps into the Snap (barrel notch), which ensures its retention and centering. The quality of this fit is important: a Snap (barrel notch) with correct dimensions firmly holds the cover while allowing it to be fitted and removed during servicing (replacement or Lubrication of the spring), without the cover popping off under the force of the spring or from shocks. A cover poorly held by a worn or overly wide Snap (barrel notch) may come loose and jam the Movement. The Snap (barrel notch) is made by turning, with precision, as it governs the Water resistance relative of the barrel (retention of the Grease) and the reliability of the Motor organ (power source). The term illustrates the precise vocabulary of barrel construction.