Pin Block Torque

[Ron Nossaman]

Hi Terry,
First off, 0.286 is a 3/0 (000) pin. I'd be putting in 0.282 (2/0 (00)) in
a new block. Someone (sorry, I forgot who, but I have the info in an Excel
spreadsheet if anyone needs it) posted information regarding initial torque
values in different blocks with different drill sizes with 2/0 pins, and
torque values for the same installations three years later. With the 11 ply
block you're using, the reported torque for a 0.015" undersize drill
dropped 18 in/lb in three years, from 148 initially, to 130. I don't know
what my installations torque at, because I go by the feel, and don't
normally check them with a torque wrench, but I'd think the 150 or so
initial torque is probably a better target for this kind of block. The
apparent increased torque from the bushings is illusionary. Bushings will
increase initial torque, but that diminishes quickly and they ultimately
won't add anything in the long term over what the block provides. It's not
a break even, it's a net loss. Just like there wasn't a bushing at all. The
only place a bushing helps is as a drill guide, and it changes the feel
when you're tuning. For the better, I think. (I know, I know)

FWIW, back when I was working for someone else, we used to drill 0.25" for
these blocks, and had some of them fail to the point that the pins wouldn't
hold in as little as three years in a steam heated school system. 
  
Ron N