[pianotech] Square Grand Hammer Boring Angles

[Terry Farrell]

I have a new set of hammers custom made for my 1867 S&S square grand. I think the hammer boring angles are not correct.

I'm not sure what the proper term may be, but for clarity and reference purposes I will be using the term "hammer diameter axis". By hammer diameter axis, I am referring to one of three axes of the hammer: strike point to tail (height); thickness (self-explanatory - about 9 mm thick); and diameter (shoulder to shoulder) - so the hammer diameter length will vary from maybe 1-1/2" in the bass to about 1/2" in the high treble. I hope that is clear.

To the best of my knowledge, it seems to me that the hammer boring for an American square grand piano should result in the diameter axis of each hammer either being parallel to its respective string(s), or if not parallel, then purposely angling the hammer diameter axis a few degrees toward parallel with the hammer shank. Is that correct? Should hammers be bored so that there is always some appropriate bias toward the hammer diameter axis being more parallel with the hammer shank?

On the set I have, the bass hammers are close to parallel with their respective bass strings, but starting in the low tenor and going up the scale, the hammers start to diverge from being parallel with their respective strings, but the deviation from parallel with the respective strings is toward the diameter axis of the hammer being perpendicular to the hammer shank - not parallel with the hammer shank. I'm sure you can easily imagine what kind of hammer clearance problems that produces.

I'd just plug the entire set and rebore them, but I don't think my Renner hammer boring jig will accommodate square grand hammers - and besides, I've already chewed the heck out of the bass hammers trying to get them to clear their neighbors.

Looking for a reality check here.......  :-(

Terry Farrell