Tuning pin choice

[Paul Chick (EarthLink)]

 Double drilling the Delignit then indicated to me that my previous drilling
technique was considerably more responsible for torque variations than were
pin differences in the Denros.
>
> HI Ron,
>               I have found the same thing, double drilling is the way to
> go. Factories can control the rate of feed, most of us can't.  Probably
the
> temp of the drill bit has a lot to do with it.
> Regards Roger

I was using this technique also, then did some testing with a parabolic bit.
Several dozen holes were drilled  into multi-laminate rotary cut stock with
the double pass method with jobber bits.  The second pass removed
approximately .020".  Then a few dozen holes were drilled in the same
material with a parabolic bit.  Miked pins were driven into some of the
holes followed by a series of turns on the pins to simulate restringing,
minus the string.  One could not tell/find the difference.  The remaining
holes were sawn open and examined under magnification.  Wood fibers had
nearly identical cuts  with almost no tearout and almost no surface glazing.
The parabolic bit ran cooler, took less power,  and could not be loaded with
chips through the 1 3/8" stock  Pins were tested several months later, again
no difference could be felt.
The bits are available form machine shop supply companies.

Paul Chick