Machine Head

Paul Mallen in his introductory post has said that he wants to make his own guitar machine heads. All the instruments that I have made so far have used tapered wooden pegs so I have never really considered the matter. Here are a couple of pics of one of the tuners on my Amalio Burguet classical guitar.

My interest is piqued. What is the gearing - Helical, cycloidal, involute, worm and wheel? And how are we going to go about making one these? Or at least something that works in a similar fashion. Paul mentions a bass guitar which, I believe, uses a lower gear than a classical guitar.

Cheers,

Rod

Edit :Mallen not Masson (plonker )

Edited By Roderick Jenkins on 18/08/2020 12:06:39

Superficially a worm mating with a helical gear, and involute tooth form. However, the width of helical gear is quite small so I suspect the teeth are simply straight cut at the nominal helix angle rather than being cut on a helical path.

Andrew

Hi Rod,

That one looks involute, I have an old banjo mandolin where the cuts look more like splits cut in the worm wheel!

Also odd ones on this Walthari Mittenwald mandolin, mid 20th century. A very skinny thread, they appear gashed as triangular tooth-spaces then hobbed or just worn to a slightly enveloping profile for the very skinny worms whic appear to have been cut with a round-nosed tool.

All my modern instruments (that use this type of tuner) have what appear to be involute gears cut to match the helix angle of the worm. They generally appear to be hobbed and so partially enveloping the worm. I'm sure my oldr instruments all have less 'engineered' arrangements.

I'm sure pretty much anything will work, but a well made involute-based worm and wheel is probably going to give the smoothest action.

Neil

The Worm in Rod's photo would require a bit more than basic screwcutting as the depth is greatest in the middle and feathers out at each end. Andrews Copy attachment would be ideal or a template made to hold the free cross slide against as the cutter moved along the lathe's axis. Alternative would be a "v" shaped cutter in the CNC with 4th axis.

As Rod likes his woodwork it may even be possible to make a cutter that could be used much like a Sorby texturing tool to cut the worm which would just need feeding straight into the work and the angle of the spinning cutter's teeth would produce the helix.

Edited By JasonB on 18/08/2020 13:14:13

Cycling to work a couple of months ago at the roadside near a school I found the sad remains of a cheap electric guitar, body smashed but the neck extant with 6 tuners. Naturally I squirreled it though I have no interest in making a guitar. The tuner gears are completely enclosed. HSE version for kids perhaps. Should it just go into recycling or do home guitar makers use bits like this? Can't think of an ME use.

The heading photo is of a mass produced item, pity about the cross head screw, so the spec is going to be "yeah, like some grooves sort of at an angle ok?"

Is the machine head not the piece of wood that the machines are fixed to? A headless guitar will have the tuning machines at the body end.

Mike