Center pin tension is essential to the correct function of the action, as well as touch balance. Therefore, when we change flanges we must be careful they are even in tension when replaced, so that they do not alter touch weight.
With time the loop that holds the spring in tension decays:
Old flange center pin being pushed out to release the old flange:
Joining the new flange to the hammer
Here a bushing is being reamed to optimum tension. We measure the tension in how many swings the hammer can make before it stops. Optimum 7 (with low humidity), 10 if working in a humid environment.
New pin tension tested to see if the joint functions at the right resistance.
Cutting the end of the pin off
Re-attaching the spring. This spring pushes the hammer backwards.