This may have been discussed on the Cafe before but there still is some confusion about identifying the so-called “worm over” and “worm under” style of tuners. “Worm under” tuners have the worm closest to the string nut.
I created this simple visual guide as a supplement to Paul Hosteler’s (rip) excellent tutorial.
http://www.lutherie.net/mandolin.gear.direction.html
The visuals only allow you to identify at a glance which type you have, it does not address other variances such as the post spacing, post diameter or gear ratio. With this guide you’ll be able to tell quickly wether those orphan or new tuners are the right type for your instrument.
Notice that the “worm under” type have a right-hand threaded worm. A right hand thread is the common type when we think righty tightly, lefty lucy in our every day world and having nothing to do with mandolins. The “worm over” type have a left-hand threaded worm. As Paul explains this was done so that the tuner knob turns in the same direction as the “worm under” type. The left-hand worm may have been the genesis of the use of “reverse thread” or probably later “reverse tuner” again having nothing to do with the tuner knob being turned in reverse, this is not the case.
For you terminology buffs here is the meaning of right hand or left hand threads and an exercise.
Hold your right thumb out and curl you fingers around as if you were hitch hiking in the US, now point you thumb away from you. The thread will cause the shaft to move in the direction your thumb is pointed when turned in the direction your fingers are curled. This makes it a right hand thread. Now try it with your left hand. Easy, right?
With Gibson the change from worm under to worm over tuners seems to have occurred somewhere during 1925.
I hope some of you find this useful.
Mark
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