Tuning Pin Torque - Hole Size

[Farrell]

FWIW, this is a follow up to my recent thread on tuning pin hole size as it relates to torque in a quarter-sawn pinblock.

I just drilled and installed 2/0 tuning pins in a quarter sawn 5-layer hard maple pinblock that I will be doing soon (after it gets my next soundboard) - a Baldwin grand. I made the pinblock myself. I used the two-drill-bit method and drilled the initial holes with a 0.247-inch diameter bit. Pianotek sells a 0.255-inch dia. bit that they recommend for the Bolduc blocks. The final holes were drilled with five different sized bits (three holes of each size) and the initial torques in in.-lbs. follow (my torque wrench only reads up to 200 in.-lbs.):

0.255 - 250? ++ (yikes! - my palm nailer almost didn't pound this sucker in - now how do I get it out???)
0.260 - 250? +
0.265 - just over 200 (about 220?)
0.270 - 140/140/160
0.275 - 110/100/90

I drilled the 0.265 holes into a Bolduc block on my current stringing job and was getting 180 to 200 in.-lbs. of torque - so this seems consistent with the above test (the above test block above has the top 3/8" in several thin scewed laminations - that may account for the slightly greater torque with the 0.265 bit on the test block compared to the Bolduc block).

I won't be doing final drilling on the test block above for a couple months likely, so I will monitor torque during that time. Initially though, it looks like the 0.270 bit will give me a nice job - maybe settling down in the 110 to 120 in.-lb. torque range?

One thing that surprises me is that it is only 0.010 inches to go from way to tight to too loose for initial torque! Not much leeway - and from what I understand, one will find even less leeway on a harder block (Delignit, Falconwood, etc.).

Thanks for all the input on the previous post. Part of my deal was just that not having drilled many blocks, I was uncomfortable when I was heading outside what I had read as being "normal". I'm much more comfy with that now.

Terry Farrell