When your mechanical clock needs to be wound, you need a clock key. … On the back of your clock is the winding arbor (the steel shaft the key fits on to). With your digital gauge, measure the square shaft from flat side to flat side to get the millimeter size.

Are clock keys universal?

The style and design of a particular key means it will not always be suitable for every clock. Mantel clocks & French clocks will use either a standard Brass butterfly key or Steel bow type key.

How do you wind a clock without a key?

If your clock has functional hanging weights and a pendulum, you won’t need a key for winding your clock. Instead, you’ll need to raise the weights using the special crank that comes with the clock. While you’re cranking the weights up to wind the clock, take care not to lift the weights by hand while doing so.