TO LET DOWN

To let down consists in voluntarily releasing, in a progressive and controlled manner, a spring held under tension, in particular the Mainspring of a mechanical movement. On a watch, the horologist (watchmaker) disengages the Click from its teeth on the Ratchet wheel of the barrel then holds back the Crown, which he allows to turn slowly in the opposite direction to winding, in order to dissipate the stored energy without any sudden jolt. On clocks and timepieces with weights or a large spring, this operation is often carried out with a suitable letting-down key, as the force involved is much greater than that of a watch calibre. Complete and controlled letting down is an essential prerequisite for any disassembly: working on a Movement wound exposes it to the risk that a spring may suddenly release, project components or damage the Train (wheel train). Movements featuring a striking or repeating train have their own Barrel to be let down separately. Letting down is the opposite of Winding, which on the contrary consists of putting the spring under tension when winding.