<html> <body> Keith, <x-tab>        </x-tab>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. <x-tab>        </x-tab>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: <blockquote type=cite class=cite cite>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 --- Checked by AVG anti-virus system (<a href="http://www.grisoft.com/" eudora="autourl">http://www.grisoft.com</a>). Version: 6.0.459 / Virus Database: 258 - Release Date: 2/25/2003</blockquote> <x-sigsep></x-sigsep> Greg Newell <a href="mailto:gnewell@ameritech.net" eudora="autourl">mailto:gnewell@ameritech.net</a></body> </html>