Bit sizes are highly dependent on drilling equipment, block fabrication, length of pin, and drilling speed to name a few. I have spent much time trying to nail a mid-range torque that is reasonably consistent pin-to-pin, and that does not loosen up too much, after one or two years.
Experimented with high precision machines, timed plunges, metric between size bits...you name it. The inconsistency remains no matter the configuration of the equipment, including double drilling. Not sure what your end game is, but trying to target an "ideal" torque from the get-go, will probably (note the probably) end up too loose too soon. Also torque reading with and without string tension on pin will increase by apprx 25inlb from a pin with no string load.
I have accepted a tighter block to start with, and learned to tune a tight new block with a longer length (15.5") lever.
If you want to experiment with in between sizes, Guhring has series 549 bright fast spiral bits in the entire 6.0-6.9mm in-between area you are looking for. Quite expensive and shipped from Germany, two day delivery. I get my Guhring bits ordered and from Butler bros 207 784-6875. Very nice bits though.
Another option is, if G is too loose, use a longer pin and set the pin down deeper. Down side on this is, static friction will increase at the bottom of the pin. This is a pain to tune, as the pin will have more internal twist to compensate for. One wants the tightness up at the top 10mm of the block surface, not at the bottom of the pin.
However, anyway we collectively skin the cat...we lose...Goldilocks torque in a new block, that is, Goldilocks torque that does not become a marshmallow in 2 years is elusive. And...all the above changes somewhat, depending on the area of the country the piano is drilled at and that the piano lives at...and the RH control of the building. For these reasons, as I mentioned above, I shoot a little tight, exercise the pins if necessary, and use a long stiff lever to tune.
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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
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Original Message:
Sent: 01-21-2018 15:12
From: Jon Page
Subject: Searching for Pinblock Drill Bit
There is none. Unless you can find a 6.5 mm bit. I usually use an F bit for most of the block and a G for the top half octave or so. But it's been a while since I drilled a block. AN F bit produces a nice feel, why would you want something tighter?
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Regards,
Jon Page
Original Message:
Sent: 01-21-2018 14:31
From: John Minor
Subject: Searching for Pinblock Drill Bit
Posting for a colleague:
Seeking source for custom drill bits. Specifically, fast spiral, high helix bits for drilling pinblocks. More specifically, a size or sizes between an E (.250) and an F (.257).
John Minor, RPT
University of Illinois School of Music
jminor@illinois.edu
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John Minor
University of Illinois
jminor@illinois.edu
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