Loose Tuning Pins
By John A. Tuttle
I've followed the articles on loose tuning pins with interest but find one more condition that has not been addressed. Occasionally, a piano will come off the assembly line that has a few loose pins. Here's what I do.
Preliminary action for steel strings: Loosen the 'bad' pin and the string's corresponding pin in equal amounts until there is no tension on the string. This prevents 'dragging' the bend (at the bottom) around the hitch pin and the bends across the bridge pins when the tension is put back on the string.
Secondary action for grands: remove the action and support the pin-ply with jacks and blocks designed for that purpose.
I remove and measure the pin with a micrometer. Bore the hole to the next pin size. Select a pin that is identical in length and type (blued or nickel plated) to the original but .006 larger than the bit. Apply driving fluid (Pin-Tite) and tap the pin in about 1/3 of the way and test the torque. It should be at least 8 ft./lbs. in either direction.
If the torque is adequate, I drive it in until about 1/4 in. of 'thread' still shows and attach the string. As I set the coil and the tab, I'm also testing the torque as compared to the previous test. Finally, I knock the pin into the height of the surrounding pins and bring the string up to pitch. I believe optimum torque to be 12 ft./lbs. (All the while I am raising the pitch of the sister pin.)
The most typical problem I have found in newer players with sporadically loose pins is the lack of threads. A few I've pulled out had no threads at all. (Can't imagine where the stringers head was at).
The other problem, which I must rationalize is an 'oversized' hole, must be the use of a worn bit or wobbly cutting. In these cases, the first torque test usually reveals the problem and I select a bit that is two sizes over and corresponding pin. Actually the torque test decides if the pin is the right size for the job.
Although selective pin replacement is almost always effective in new players, I find it less effective as the age of the instrument increases and, in such cases, I also use it as a gauge for determining the need for new strings, pins, bushings and (in grands I prefer to replace the pin-ply) boring the pin holes two sizes over.
In closing, I like to say that I found Craig Brougher's article on loose pins very accurate. I would hope, however, that any technician worth his weight would use jacks and blocks before banging away at the tuning pins.
(Next week, "Jumpy Pin Horror Stories") :-) Just kidding.
John A. Tuttle "Self-Playing Pianos" http://www.playercare.com
407 19th Avenue Pri E-Mail: JohnTuttle@PlayerCare.com
Bricktown, NJ 08724 Secondary E-mail:tuttleja@concentric.net
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(Message sent Sun 2 Mar 1997, 23:18:50 GMT, from time zone GMT-0800.) |
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