pin driving fluid

[Ron Nossaman]

>I have used thick Shellack, and it does seem to make for smoother pins, tho
>I have this feeling it tends to lessen torque... tho I have no way of being
>sure on that, just seems like every time I have used shellack the pins
>arent as tight as I'd like them to be.

My impression is that rosin lessens initial torque too, but not sliding
torque, because torque isn't necessarily torque, or it is, but it depends
on what we're measuring. We're dealing with two different things when we
talk about pin torque. First, there's static friction, which determines how
much oomph it takes to initially get a pin moving. Then there's sliding
friction, which is how much oomph it takes to KEEP an already moving pin
moving. The farther apart these two values are, the more inevitable are
jumpy pins. If the static friction is significantly higher than the sliding
friction, the top part of the pin is torqued far enough past the position
of the bottom of the pin before the bottom breaks loose and slides that
when the bottom does move, it catches up with the top all at once, since
the sliding friction is low, and gives you the beloved "snap". When the
static friction is very close to the sliding friction, the top of the pin
isn't twisted significantly past the bottom portion before the bottom
portion breaks loose and slides at about the same rate as the top, though a
little behind, and you get a smooth turning pin. There isn't any one thing
that is a mystical magic elixir for this purpose. Shellac, varnish, talc,
rosin, or anything else non corrosive that doesn't evaporate and sets up
this condition at the interface between the pin and the block will have the
same effect. Nothing at all works quite well too with the current cut
thread pins if you can keep your hands clean and dry when stringing. The
rosin et all is just added assurance (buffer) toward establishing the ideal
interface. It's not the product, it's what the product does that counts.
That's really all there is to it. 

Ron N