Ron says: >I don't know when, but why is fairly straightforward mechanics. >These tips screw on. With no means of pinning or keying to keep the >tip on the head under the often extreme counter clockwise torque we >put on them lowering pitch in a new Baldwin or Kimball, the thread >pitch has to be fine enough to meet at a low enough angle >(perpendicular to the central axis of the tip) at the given diameter >to produce enough force when they are tightened down to produce >enough friction to keep the parts together. Sort of a helical Morse >taper system. Too coarse a thread will break loose under tuning >counter-torque levels, and too fine a thread is more difficult to >make and maintain tolerances during heat treating, and won't be as >strong. A larger diameter could use 28 TPI, smaller 32 TPI. The >thread slope is the key. Mechanics obviously calls for a fine pitch thread for the reasons Ron suggests. But I don't buy that tuning tips couldn't have functioned perfectly well without the need for using a non-standard 30tpi. Just as in ALL other products with threads the difference between 28 and 32tpi is a perfectly small step that you don't get painted into a corner and find 28 too coarse and 32 too fine. Otherwise there would be some products in the wolrd other than tuning tips and coleman camping stove valve screw seats that use it. [one could speculate on the reasons for the latter product using 30tpi] >One lathe can make a whole bunch of tips and/or heads in a day, and >a decent machine shop can make any size or thread pitch tap they >like. That's hardly a deal breaker. So tell me, with what easily >obtained and used tool would the rabble broach that tapered 8 point >hole to fit the tuning pin? A competent blacksmith would have no problem with the broaching, but I doubt they would have a lathe to turn a 30tpi thread, or even any machine thread. I was speaking tongue partially in cheek here, but the curious question still remains: when and why? There doesn't seem to be any 30tpi historical thread pitch in any system I've come across, not even weird ones from 1900 if we suppose the when goes back then. So why choose something that has never existed and makes life difficult and requires a non-standard tooling? There must be some rationale to that choice, when a 28 or 32 would function perfectly well. I still suspect a commercial regulatory-type rationale is behind it. In my particular situation one of the five lathes in the machine shop here has a 30tpi setting so it's no hassle to make the one-off male thread I need. If I was making multiple threads I'd probably make a tap and die set, which is presumably what the current lever parts makers must have done to make their tips and heads. A tuning tip might be mundane, but it is pretty much ubiquitous amongst piano tuners, so it shouldn't be an uninteresting question to ponder the origins of this "standard" - why and when was this pitch adopted for tips? Stephen -- Dr Stephen Birkett, Associate Professor Department of Systems Design Engineering University of Waterloo, Waterloo ON Canada N2L 3G1 Director, Waterloo Piano Systems Group Associate Member, Piano Technician's Guild E3 Room 3158 tel: 519-888-4567 Ext. 3792 fax: 519-746-4791 PianoTech Lab Room E3-3160 Ext. 7115 mailto: sbirkett[at]real.uwaterloo.ca http://real.uwaterloo.ca/~sbirkett
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