[CAUT] Tuning Pin Questions - The truth about reverse thread pins.

[Ron Nossaman]

> Yes I often wondered if the reverse threads weren't just a side-effect 
> of the way they cut the threads, that some salesman who happened to have 
> a silk handkerchief discovered by accident. Apparently the ratcheting 
> effect is quite apparent in silk; more dubious is the effect in 
> laminated maple or beech.

The reverse thread effect is a non-event in a pinblock. It's 
only good as a sales demo, either demonstrating conclusively 
that their product's pins will hold, or their competitor's 
pins will tear up the block.

Here's the deal. This effect is an artifact of cutting pin 
threads. Cutting threads typically produces more uniformly 
sized, parallel, and round pins, which can generally be 
considered to be a good thing, but what about the teeth?

The first time you turn a cut thread pin in a block, the 
"teeth" that aren't knocked off by the process fill with wood 
scraped from the side of the hole. Having no where to go, this 
wood dust stays in the teeth, preventing further cutting by 
said teethoids.

Now, If the static friction between the pin and the block is 
much higher than the sliding friction between the pin and the 
block, the pin will snap and pop as you turn it, loading in 
torque, until it breaks free and catches up in a hurry. Think 
Baldwin, Kimball, and the Audubon bird call, as well as 
various turkey calls. http://audubonbirdcall.com/ The wood 
trapped in the teeth of the cut thread pins both lowers the 
static friction some, and raises the sliding friction a bunch 
(skid control), so when you turn the pin enough that the 
bottom starts to move in the block, the static friction is 
close enough to the sliding friction that there is no catch up 
"snap", and the pin turns smoothly and controllably.

That's it. The rest is cosmetics and sales games.
Ron N