Tuning machine maintenance II  - alignment and fit

You probably got to this page from the first one, here. This page covers other things that I hope will help you make your tuners work better. Some anatomy:

Again, I'd venture to say that 99% of gear replacements happen unnecessarily. Players perceive a problem—they think they're worn, stiff, won't hold tune, they exhibit slop, whatever—and decide to replace them to solve the problem. But the problems are in fact almost always:

1) simply a matter of needed maintenance and adjustment, covered in the
previous page, or:

2) an issue with the instrument that has nothing at all to do with the gears, e.g. friction at nuts and saddles, which can be pursued by clicking here or:

3) mounting and alignment issues, which we'll go into here.

The fundamental issue, in any event, is friction somewhere that is causing the problems. Your task is to identify the point of friction, and take care of it.

Some terminology:

This is an understatement: hole spacing is important. The upper shaft bearing (the bushings, or equivalent) must match the plate spacing precisely.

Assuming you have done the whole tuner cleanup I lined out on the previous page,
but you find the gears don't function well when they're mounted and under tension, there are a couple of paths to follow...but first:

Eyeball the tuners to see if the entire plate is misaligned with the headstock. Ideally, it should be like this:

Note that the holes through the headstock are a bit wider than the shafts, eliminating a major possible source of friction. This leaves only two possible points of friction, as the shafts are effectively borne by the plate (orange line) and the bushings (magenta).

If the shaft spacing is correct, but the whole plate is installed wrong, some or all the shafts could be forced into going through the headstock at an angle which means the metal operative surfaces, any or all of them, could be pinching or binding.

It's a tendency of string tension to pull the posts forward, toward the nut, but if the tuner plates are mounted wrong to begin with, the posts will bind. No amount of lubrication is going to fix this, but remounting the plates will probably solve the problem. To do this, you (or your designated and supremely competent luthier) have to fill all the screwholes and start new ones so the whole plate is moved toward the nut and positioned properly and firmly so the posts can't bind.

Here's a real-life example:

These tuners really didn't work until I moved the plate. By the way, it is typical that misaligned tuners like this will bind harder and harder the higher you tune your string.

Here are a few possible ways to treat the hole through the headstock:

Even if the post spacing is wrong—irregular, unevenly spaced, incorrectly spaced—it will be relatively easy to correct that, and generally invisible as well. The bushings (if you have the perfect original ones, don't lose them!) will almost always cover the problem spot where they were moved from. Filling and redrilling the holes is not rocket science, if it comes to this.

I usually ream the post holes from the back of the headstock with a violin reamer. And it's possible to relocate the bushings to match the post spacing, then adjust the hole, then adjust the position of the plate. The only work the wood in the headstock does is to support the bushing on the face of the headstock. And hold the plate firm, of course.

Here is an example of replacement tuners about to cause more trouble than they were hoping to fix. Notice how they are splayed, not at right angles at all. The original holes were a wee bit farther apart than the new tuners require. Note that the plate is still not touching—because it can't. These tuners will never work, but moving the holes a wee bit closer together, and opening the holes through the headstock from the back, will take care of the problem.

Here are two failed attempts at making gears with no slop, as if that was ever needed. The first was an effort by Kluson, during their dying whimper before going out of business in the 1970s. 20:1 ratio, they were awful!:

And here's Grover's answer, an even less-known market flop:

Tons of friction, it took forever to get a string up to pitch. What were they thinking?

I find any machine ratio over 12:1 to be unnecessary.

The previous page to this one, about mandolin gear function and maintenance
More mandolin gear stuff such as  mandolin gear direction here

Information about new and old Gotoh mandolin gears here

My home page here and my main lutherie page here  and my site map

What more could you want?

Oh yeah. Questions? Have more info? Please drop me a line by clicking here

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