Thursday, 4 September 2008

A locking nut that didn't work

Since I put the T-beam guitar on hold for a while, I bough a cheap Gibson SG copy for various experiments. One of the first things I wanted to try out was a tuning system, which uses a locking nut in combination with a Schaller 456 fine tuning bridge

I need to be able to rough tune and lock down each string separately, so the usual ones with two strings per screw won't do. According to the idea, after rough tuning, the fine tuners in the bridge take care of further adjustments.

For some time, I've been looking for a suitable locking nut. After a while without identifying anything useful off-the-shelves, I decided to make one myself.

I started with a piece of 7075 T6 aluminium. I drilled six holes for the string locking screws and two for screwing the locking nut on the headstock. I then threaded the holes (M4).

I then made six grooves; one for each string.

...and filed the grooves smooth.

I mounted it on a piece of brass on the headstock, but the D string snapped when I tightened the screw. On closer inspection, the screws turned out to have very sharp edges, which explains why the string was cut. I'll have to file the ends of the screws flat. I'll have to shorten them a bit anyway, so that's no big deal.

Unfortunately, there was another problem as well: The pressure of the screws lifted the nut off the brass plate (the picture shows the gap between the aluminium nut and brass plate). That can probably be solved by making the nut a bit deeper and having two mounting screws on each side of the string locking screws rather than only having one set of screws.

I'm going to give it another try some day and make an improved version.

Btw, if it had worked, I would have bought six proper set screws for it and cut off the remaining headstock. In an artistic fashion, of course ;-)