uprights, hammer boring

[Keith Roberts]

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I gave the technical on hammer boring at the chapter meeting, (with the =
back-up of the RPTs at the meeting), and nobody could explain what the =
criteria would be for determining hammer bore distance and rake for =
optimum performance on an upright. Sure, go by the original is an easy =
answer but what if it looks as if somebody who "hadn't a clue" put those =
hammers on. I have 3 old uprights here, a 1909 Smith and Barnes, a 1911 =
A.B. Cameron, and a 1906 Kohler and Chase. The first two, the hammers =
shanks are close to parallel with the string plane, and the rake is =
minimal. Or, worded differently, the bore distance is the distance from =
the hammer flange center pin to the string plane. Rake is 1 or 2 =
degrees.=20
The Kohler has much more rake, 5+ degrees and the shank is at the =
similar angle to the string plane so the hammer is square to the string =
plane when it hits.
Why?
Should I be looking at the angle of the jack to the whippen at the start =
of lift? The hammer butt/jack angle at let off?
Or maybe it was something simple, like the little bit more clearance =
that could be had by moving the action closer to the strings.
Anybody?
Keith Roberts

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