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Hello friends.
here is new and different topic for discussion.
im in process of building own tuning keys for classical guitar and later on for acoustic guitar.
i have almost finalised 0.6 module worm gear with 18 teeth.
after discussion with a owner of workshop for teeth cutting of the gear the main topic was
how to engage the roller shaft in the gear.
in many keys its double D slot and in some it is broached in square form.
after checking some machine makers website. i saw that some use press fit joint to engage the roller.
i told this to the workshop owner and he said that tolerance for press fit is 0.1 mm
and after press fit it removes some material from the gear so the grip becomes little loose and may cause problem in future.
he told me to find how much torque is needed to tuning the keys
so i want to ask can anybody tell me how much torque is needed for both acoustic and classical guitar strings so that the roller shaft doesnt slip
and anybody have used the keys with press fit and have any problems o no.
thanks in advance

Really, really rough math here:
For Medium D'Addario Phosphor Bronze EJ17s, the 4th string, tuned D3, at 0.035" diameter, has a string tension of approx 35.87 lbs

Let's take steel string Waverlies, with a .249" diameter string post - it's actually slightly narrower at the string hole, but I'm going off of memory here.

Force x Distance = Torque
35.87lbs x .125" (radius of the tuner post) = 0.374 foot pounds ( or .507 newton meters)

Can anyone confirm, or correct my math?

For a press fit that small I would think it would be more like .01mm, not .1.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.