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I've seen the term "bobbling" used a few times. What does it mean when you say the hammer bobbles?

It means there is a promlem with the escapement (also known as either set-off, or let-off).

This means the jack does not properly clear away from the notch,

so the hammer 'bounces' on the top of the jack,

causing it to 'bobble' on the string.

The sound it makes is like a rapid repetition.


It is usually easily cured by a simple regulation of the action.

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Instead of striking the string once per keystroke and then moving away from the string rapidly in order to allow it to vibrate to its' full potential, the hammer strikes a second, or even third, time, thereby interfering with the string's vibrational energy. This can be caused by several regulating issues, such as improper checking of the hammer and repetition springs that are too lively.

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Usual other causes are badly worn checks or balance hammers (uprights),

or incorrect adjustment of the checks.

If this is the case then the spring tension may be too strong for the

worn checks to hold the hammer after set-off.

The result is the same though,... that pesky bobble!
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