MIMF

A lot of tuners have removable buttons. I'm not sure if it is standard but it seems like there are a lot that have a round shaft with two flat sides and a threaded hole in the end. I think these are the dimensions-
Flat side to flat side of hole = 1/8 in. (3.2mm)
round side to round side = 5/32 in
I am looking for a tool that would be sort of like a key or wrench that would fit this type of shaft.
Any body know what this type of shaft is called, or if there is a tool designed for it?

Why don't you just use an extra button for a wrench?

There is no name for a shaft that has opposing flats like that and there is no tool to fit them unless you make your own which you can do with a small milling machine or a home made broach. Not all the tuners use the same dimensions either.
If you happen to use Schaller tuners you can pry the metal insert out of one of their wooden tuner buttons and glue it into a "T" or crank handle.
Another approach would be to drill the O.D. hole into the end of an allen key and mill or file the flats on both sides and then bond or solder flat plates to the flats.

I'm experimenting with the gears to see if it can be used as a fine tuner for a truss rod. In the initial design, the button-less tuner sits into the heel of the neck, and the key will fit into a small hole in the neck plate.
So the key turns the worm gear, and then the brass gear is turned at a very low rate, 14:1 or what ever.
The shaft of the tuner that the string would wrap around is replaced with a screw, which fits into the truss rod.
I found the shaft shape is called a Double D, but I can't find much information on small ones. They seem to be used for steering columns and slip fit drive shafts.
Anyway, there doesn't seem to be a key like this, so for the prototype I'll epoxy a little socket screw into where the button screw was. I'll look at some Schallers if this actually goes anywhere.
For the piece that connects to the truss rod, a 6-32 machine screw seems to have a 5/32 shoulder, so I think I can just take a bit off the sides so it will ride in the D slot of the Brass gear.

Have you ever seen a truss rod out of a Burns guitar? That's essentially what you'll have. It was called the Burns Gear-O-Matik Truss Rod. I think those may have used a planetary gearing system but it is a right angle shaft.
I can post a photo or two if you are curious as I have one here. They weren't particularly reliable but they sure were complicated and confusing to the uninitiated.

Well, those aren't exactly by target attributes, but yes, I would like to see the Burns pictures.
Thanks

hmm, if it's ok to have a permanent attachment and the looks aren't too important, then a socket-head screw epoxied in place might be ok. I'd use J-B Weld on the screw threads with a dab extra, and then also slip a piece of metal tubing over the socket-head and the shaft. I did something similar but on a huge scale a long time ago, when a neighbor needed a wrench/socket that was way too expensive for what it was used for. And oddly enough, I don't remember what he needed it for either!

The socket screw actually looks fine and will be recessed behind the neck plate with just a little access hole. It may need a little tube or some washers to put a little pressure to hold the gear in the housing properly.
It's actually an M7 screw that has the 5/32 shaft that can be filed down to fit the Double D slot in the Brass Gear. The screw in the truss rod is a 6-32, so I'll need to get a new tap.
I'll probably drill the truss rod slot a little lower in the neck so there is more meat on top. Then the whole contraption can be set into the neck heel.
I'm wondering about stresses. I suppose it could have the same stress as all 6 strings combined?

Dave,

Here's a thread where I posted a photo of the rod i have.
http://www.mimf.com/phpbb/viewtopic.php?f=4&t=2099
Let me know if you need more info. You can still buy the rods from Burns of London website for 165pounds ea. Not sure what consortium of investors took over the brand but they clearly have no shame.

Dave,

Here's a thread where I posted a photo of the rod i have.
viewtopic.php?f=4&t=2099
Let me know if you need more info. You can still buy the rods from Burns of London website for 165pounds ea. Not sure what consortium of investors took over the brand but they clearly have no shame.

It must be the same hedgefund humanitarian who bought the old antibiotic drug and immediately raised the price by 5000%.