uprights, hammer boring

[Greg Newell]

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Keith,
         I believe that Newton Hunt wrote something about this a while back 
on this list. You could search for it in the archives. If you find it feel 
free to repost. I'm sure many would be interested. I seem to remember that 
bore distance was the same as a grand in that butt flange center pin to 
string is the bore distance. As far as rake goes I really don't remember. I 
don't replace a great deal of hammers myself.
         This brings up a question for me that perhaps someone can answer. 
Although I don't replace many sets of hammers on uprights I presently have 
occasion to replace a set on an old Gulbransen upright. I tried to measure 
from the butt center pin to the string and I just couldn't get a measuring 
device in there to take the measurement. Anyone have a tip on what I could 
use to get a good reading? Might be too late for this set but I'd sure like 
to know for the next one.

Greg


At 05:28 PM 3/12/2003, you wrote:

>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.
>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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Greg Newell
mailto:gnewell@ameritech.net 

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