MIMF

Has anyone here used these on a guitar with a regular peghead? I'm interested in trying them on my next solid-body electric, but they're kinda pricey and I'm wondering how well they really work.

https://www.stewmac.com/Hardware_and_Pa ... uners.html

I'm wondering how they work, it's kind of hard to have a gear ratio (40:1) without a gear... Probably planetary, I figure.

It is a threaded post.

That makes sense. The tuning knob sucks the string lock down, tightening the string. As an engineer I object to the description of a 40:1 tuning ratio, it might have 40 TPI threads, but as the driven post does not turn, there is no ratio.

Edit: but there is an equivalent ratio. If they indeed use a 40 tpi thread (very common, used in all imperial micrometers) one turn begets .025" of post movement, hence string longer or shorter by .025". To get .025" of string movement on a notional worm geared tuning machine, with a post diameter of .200" (about close to right) you'd look for a 25:1 gear ratio. Alternatively, if you wanted to have the equivalent of a 40:1 worm gear with a .200" post using threads, you have 63.7 TPI.

Has anyone here used these on a guitar with a regular peghead?

I've used them on a guitar with standardish strat style headstock.They work fine although there's little advantage over standard locking tuners other than looking a bit different. I seem to remember there were some quality issues with them at one time which is maybe why they've been off the market for some while. I've never had any problems with mine though.