I agree with Clyde. I usually put a pipe clamp on either side of the bolt I am installing - yes, that may mean up to 10 pipe clamps - argueably overkill, but especially with a large separation its pretty close to necessary). Then tighten a little here, little there, and so on down the line. I did a Baldwin Hamilton a while back with a 1/2" to 1" separation across the entire back. It was a lot of work bringing it back together with the ten clamps - and that was with tension down two full steps, and I did not quite get it completely back together - but at least the damper were rising from the strings (that was the original complaint from the customer - the plate was so bent over, the dampers were not able to lift from the strings!). Terry Farrell ----- Original Message ----- From: "Clyde Hollinger" <cedel@supernet.com> To: <pianotech@ptg.org> Sent: Thursday, September 20, 2001 10:31 PM Subject: Re: Bolt strength > Bob, > > I don't know the answers to all of your questions, but I have repaired two or > three separated Everett backs, using 5/16" carriage bolts and epoxy. No further > problems. You understand, I presume, that the back is pulled together with > clamps first, not just with the bolt. I think that wouldn't work. > > Regards, Clyde > > BobDavis88@AOL.COM wrote: > > > Subject: Everett studio, pinblock separating from back > > > > I need to bolt this sucker back together. I have done this repair twice > > before with half-inch bolts (w/long-term success), and I know others have, > > but I would like to take a fresh look at this from the perspective of the > > engineers out there. > > 1) I chose bolts empirically, and they worked. However, is there anyone out > > there who knows the tensile strength of various diameters of bolts? Of > > hardened bolts? > > 2) How much strength do I actually need to resist breaking or bending of the > > bolts? > > 3) Is there an advantage or disadvantage to hardened bolts in this > > application? > > 4) Is the separating force the only one I need to worry about, or should I be > > worrying about the shearing force tending to collapse the plate? > > 5) In re: above, I have always assumed the bolts did all the work, and that > > the glue line was contaminated/dirty enough it wouldn't cinch up completely. > > Is there a glue better than Titebond for resisting creep in a glue line which > > is both dirty and not as thin as it should be? Weldwood? Polyurethane > > (Gorilla) glue? Are both the adhesive and cohesive strengths of epoxy > > sufficient? > > Thanks, engineers, > > Bob Davis > >
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