Tuning pins with teeth

[Brian Lawson]

"If you are going to do this stuff, you should at least attempt to be a
scientific as the marketing folks were.  "

To make it scientific wear a white coat and have a clipboard and pen at hand
:)


Brian Lawson
PTG Assc, MPT.
Johannesburg, South Africa







!

On pins and needles, we still await the true test of tuning pin
functionality...

Regards,

Del

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----- Original Message -----
From: Ron Nossaman <RNossaman@KSCABLE.com>
To: <pianotech@ptg.org>
Sent: February 28, 2000 4:22 PM
Subject: Tuning pins with teeth


> I just tried a little experiment out in the shop. I took four new cut
> thread tuning pins and a scrap of Baldwin's pinblock. I figured that if
> anything would strip the thread burrs off when the pins were driven in,
> it's that block.
>
> Drilled four "I" holes and drove in the pins to the same height, and about
> as deep as they would be in a real piano. Two of the pins, I took counter
> clockwise torque readings, followed by clockwise readings. On the other
> two, I took clockwise readings, followed by counter clockwise. The idea
was
> to see if there was more initial resistant to movement in one direction,
> than in the other. The torque peaked around 25 foot pounds either
> direction, and settled immediately to around 20 after the initial
movement.
> There was no discernable difference in torque values between clockwise,
and
> counter clockwise movement of any of the four pins.
>
> Next, I turned two pins clockwise 180°, then back to their starting point.
> The other two, I turned counter clockwise 180°, then back. Torque readings
> were similar coming and going on each of the four pins.
>
> At the bandsaw, I cut to within a millimeter of each pin from both
> directions and broke the block apart to get a look at the pins without
> further twisting them. About half of the threads ( those that protruded a
> little further, I suppose)  were filled with sawdust.
>
> current conclusions:
> 1: The "one way" nature of the thread burrs is, as suspected, nonsense.
> Rebuilders have always known this to be the case, so why hasn't every
piano
> tech with this question tried this experiment for themselves?
> 2: The thread burrs are not taken off during driving, and survive enough
to
> provide some initial resistance to turning as they bite into the block and
> fill with sawdust.
> 3: The thread burrs don't continue to chew up the block because they are
> immediately filled with sawdust with the first turn, clogging the burr
> "tooth", and the sawdust has nowhere to go to clear the burr for another
bite.
> 4: The sawdust between the pin and the block, trapped in the threads,
> lowers the static friction, and raises the sliding friction, so the
> transition is smoother when the pin is turned. It slides smoothly instead
> of jumping.
>
>
> In the interest of symmetry, I cut apart a block in which a pin had been
> driven, but not turned. There was not nearly as much sawdust in the
threads
> as those which had been turned. So far so good. I then put the block
halves
> back together, clamping the halves in a vise, and cranking the pin back
and
> forth. When I took the block apart again, the pin hadn't picked up any
> additional sawdust that I could tell, but there didn't seem to be that
> initial resistance to turning at the first movement either. This one was a
> tad on the inconclusive side, and just serves to supply some contradictory
> evidence to the above experiment, lest anyone be too easily convinced.
>
> That ought to get you started. Go forth and ponder.
>
>
> Ron N