Vintage Tuner Rehbilitation Question

[Rob Gerety]

The tuners on my 1916 A4 are lovely but several of them are stiff. So stiff that I started to worry that I might twist off one of the buttons. I do not believe the problem involves the nut or saddle slots. Although that is certainly possible. I had a new nut installed recently and the stiff tuner issue is the same with the new nut as it was with the old nut.

So I decided to do a 100,000 mile overhaul ala Paul Hostetter's web site. Everything came apart pretty well although I did have to use a drift to tap the posts off the cogs. But, they all came off without undue difficulty. I kept all the parts organized so that everything will go back together just as it was originally- same post with same cog etc. I cleaned all the parts in naptha. The truth is that that parts do not seem all that dirty.

While the tuners were still disassembled I oiled the worm gear bearing surfaces at the tuner body (where the worm is held by the two tabs or brackets) with Tri Flow. It is pretty clear that most of the stiffness in this area. Despite a fair amount of effort to get that area cleaned and lubed several of the tuners still have some stiffness. They seem to turn smoothly about half way but then they hit an area that is stiff. They do not appear to have been bent or damaged in any way and the do not exhibit much wear. They are definitely better than they were before the overhaul, but I would like to get them even smoother.

Before I put them all back together does anyone have any suggestions about what I might do to improve them further. I assume the worm gear/tuner shaft/button assembly cannot be disassembled - is that correct? Is it just a matter of lubing them well and then turning them a few hundred times?

[Bill Snyder]

Rob,
If they are like modern tuners then EVERYTHING will come apart. These are Grovers.

[Rob Gerety]

No, these are the originals. Just like the tuners shown in Paul's piece on tuner maintenance here http://www.lutherie.net/tuner.maintenance.html, only mine is an A.

[EdHanrahan]

... I oiled the worm gear bearing surfaces at the tuner body (where the worm is held by the two tabs or brackets) with Tri Flow.

I assume that you also oiled the meshing worm & gear surfaces themselves.

AND... Did you oil (Tri-Flow) the string-post/gear assemblies where they extend THRU the baseplate? That also is best done with the tuners off, as there's a fair chance of getting oil into the underlying wood - not a good thing.

If it's the fully dry (pure teflon?) Tri-Flow, that's maybe not a concern, but I could only find the oil-carrier one at shops near me, and suspect you have the same. Good luck!

And have a happy & safe New Year!

[Rob Gerety]

Yea, I did all that. The slight stiffness that remains is coming from the worm gear alone. Happens even when the other parts are completely disassembled. They are certainly significantly better than they were. But I wish I could figure out how to get the remaining stiffness out of the worm gears.

[atetone]

What I have tried a few times with some success is to turn them at high speed with a hand held drill while keeping them well oiled during the process.
I just take a socket wrench slightly bigger that the tuner button and tape up the button to protect it and then hold on tight and pull the trigger.
It beats sitting there for hours turning them by hand.

[Paul Hostetter]

I tried some of the truly dry lubes and had them kick in the bottles, into a stiff gelatinous mass. So much for that big idea.

Meanwhile, the lightly oiled iteration of Tri-Flow motors along. I think I dropped the ball on this on another thread, but someone said they couldn't see any evidence on the Tri-Flow bottle that it contained Teflon. It turns out the patent on Teflon expired and people are using the 'generic' version of it, PTFE, being the synthetic fluoropolymer of tetrafluoroethylene which is still well known by the DuPont brand name Teflon.

With regards to turning and turning, make one of these (or buy a ready-made for $18) and put it in a power drill:

http://www.lutherie.net/stringwinder.jpg

You'll get thousands of turns in moments.

I also check how the gears turn while still off the instrument, and then compare performance once they're mounted. If there's a difference, it's not the gears causing the problem.

[Rob Gerety]

I've pretty much narrowed the remaining stiffness down to the worm gears. Its the same mounted or unmounted.

Is it advisable to oil liberally with tri flow and then literally give the sticky worm gears a thousand turns? Scares me a bit to do that - I don't want to wear them out!

[Greg Mirken]

A batch of tuners that National Resophonic used once had stiff spots because something was machined off-center. At Don Young's suggestion I got a can of gear-lapping paste, squished some into the meshing gears and twirled them with my with my power driver setup (like Paul shows) for about 5 minutes. Voila! Without some grit in there, I think it would take a very long time to make any difference.

[Rob Gerety]

Well, the thing that worries me is that these tuners are almost 100 years old. While they clearly have not had that much use, I would think any ordinary stiffness would be long gone. Plus, how do I get lapping compound in the worm gear bearings?

[Paul Hostetter]

I would caution against loading old gears with lapping compound. It works with crude new ones, which we fortunately rarely see these days, but could cause trouble with old ones. Just chuck in a tuner socket thingie, carefully adjust the screw tension, add a bit (a lot is unnecessary) of Tri-Flow, and whirr away.

[mandroid]

Bill Snyder's example is from the bottom of the 'modern' range , the base plate is folded over to make a portion of the worm shaft bearing. (you can take Schallers apart, much nicer mech)

Old ones the worm shaft bushing is swaged onto the backing plate, a riveting like attachment,

several years ago I had one of those come loose , and to re rivet it I ground a concave shape in the end
of a piece of steel , and re set the 'rivet' as it pierced the base plate , using that as a support ,

so as to keep from having the hole that the worm gear end passes through not be flattened out of round.

seemed effective , been playing that mandolin for 12 years since..

[Rob Gerety]

I will admit that since the tuners are fully functional now (although a few have a certain amount of stiffness) I am nervous about doing too much for fear that I will somehow damage them. Might be the Yankee voice in the back of my head warning me "If it ain't broke don't fix it". Every time I hear that voice and ignore it I seem to create problems for myself. It is especially true when I'm working with something that I don't fully understand.

A couple of these tuners work fine around part of one full turn and then hit an area in the turn where they are tight - once you turn through that area they will turn fine until you come around to the tight area again. When they were completely dry after cleaning with naptha and before I applied tri flow a couple of them were extremely tight - almost impossible to turn. When I applied tri flow they did loosen up to their current state - but still on some there is that tight "spot" or area as you rotate through a turn. Any thoughts what might actually be causing that?

Is there any risk that while rotating through hundreds or thousands of cycles with a drill the bearing surfaces might dry out and tighten up to the point that I twist off the tuner button? That possibility is the only thing holding me back a bit from working these tuners through hundreds of cycles to smooth them out.

[pops1]

I have had tuners that the gear is bottoming out in the worm and causes it to be tight. I have used a chain saw file to file the gear down so that it won't bottom out when it is turned. It is slow as i don't spin it in a drill press, but turn it by hand, but has helped.