bizarre pitch

[Ron Nossaman]

>I haven't been able to come up with any current or archaic standard thread 
>size with a 30tpi. The finest plumbing threads (taper or parallel) seem 
>only to go to 27 or 28tpi depending on the system, but including the 
>archaic ones, so I can't see it being a plumbing legacy (and what's the 
>connection between tuning lever making and plumbing anyway). This 
>situation begs the questions when was this standard adopted for tuning 
>tips? and why? and why is it still so ubiquitously used for tuning lever 
>tips? Is this just yet another example of the piano industry being anal?

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.


>As for the how....are Hale tips made by an army of lathists running their 
>lead screws through the night in sweatshops or are special taps and dies 
>exchanged for large sums in back alleys. Maybe a subject for industrial 
>espionage? Maybe there's some sort of secret handshake to get into the 
>30tpi club. Or maybe the size adopted as the most obscure one that would 
>prevent the rabble from flooding the tuning tip market with cheap ripoffs 
>and bringing down the value of tuning tip investments?

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?

Ron N