Slotted headstock tuning machine gear replacement?

dorcus_maximus · #1 01-27-2021, 07:44 AM

I recently picked up a Yamaha FG2500. It was made sometime around the early '70s and it is (or will again be) a very nice instrument. One of the pinion (or worm wheel) gears and the screw that held it on are missing. I don't know if these things are fairly interchangeable or if I'm going to have a difficult time finding a replacement. I figured some folks around here would know.

I would very much like to avoid replacing the entire set of (12-string) tuning machines. It would probably be easier and cheaper to send one of the other gears to a machinist and get them to copy it than it would be to find a quality set of slotted head 12 string tuners and have them installed. Of course, this is assuming that the screw hole isn't stripped....which I should probably check on soon.

Mandobart · #2 01-27-2021, 10:40 AM

The worm gear is the straight gear on the shaft attached to the tuner button. The roller gear is usually screwed to the roller shaft (part the string winds on).

I'm assuming you're missing the roller gear and it's machine screw.

First you need to determine the type of tuners you have (Ping, Gotoh, Grover, Schaller, etc.). To the best of my knowledge parts are almost never interchangeable between brands.

It would NOT necessarily be cheaper to have a machinist make a replacement gear for you that matches the diameter, root diameter, helical pitch, shaft diameter and flat spacing, etc. of your existing gear. In my area it would cost $150 - $250 to take the measurements from an existing gear then make a new one. You can get a new set of tuners for less than that.

I would first contact Yamaha. They may even have parts to sell or give (I once contacted Ovation about a tuner problem and they sent me a free replacement).

Alternately, I would call a few guitar repair people. They probably have a bunch of spare parts. The only problem is finding a spare part that matches your needs exactly. I'm looking at a bag of old tuners here but have no idea if any of my stuff would work on your guitar.

John Arnold · #3 01-27-2021, 11:44 AM

The missing gear is common on open tuners, and is the reason the screw tightness should be checked periodically.
Yamahas in that time frame have tuners that are unique to the brand. I would be searching for open back Yamaha tuners on Ebay. If you are robbing the gears and screws, they don't necessarily need to be 12 string, as long as the make is the same.
While I do have a large selection of tuner parts, I would not be confident in finding a match unless I had the tuner in hand to check the fit. Tolerance on the gears is very tight.

dorcus_maximus · #4 01-28-2021, 11:13 AM

Does anyone have any idea if the tuners on this guitar are likely to the same as or close enough to the tuners on mass productions Yamahas of the same period that there is any chance those would work?

The tuners are stamped Yamaha. Did Yamaha make their own tuners or might these still be Ping, Gotoh, Grover, etc.?

I have a Taiwan built FG-45 here and I know that doesn't work. The roller gears on the FG2500 are splined on both the inside and outside (so, the post it fits on is splined as well).

dorcus_maximus · #5 01-28-2021, 12:14 PM

Here is a link to a couple of images of the roller gear and the part of the roller that it connects to. Searching online I haven't found any images of roller gears that look like this. I suppose I might be able to replace the roller and roller gear??

Brucebubs · #6 01-28-2021, 04:11 PM

Quote:

Originally Posted by John Arnold

The missing gear is common on open tuners, and is the reason the screw tightness should be checked periodically.
Yamahas in that time frame have tuners that are unique to the brand. I would be searching for open back Yamaha tuners on Ebay. If you are robbing the gears and screws, they don't necessarily need to be 12 string, as long as the make is the same.
While I do have a large selection of tuner parts, I would not be confident in finding a match unless I had the tuner in hand to check the fit. Tolerance on the gears is very tight.

Great reply - I believe these are 6 on-a-plate per side and have a tuner spacing unique to Yamaha and there is no aftermarket 6 on-a-plate that matches that spacing?

The spacing on most after market 12-string slotted headstock 6 on-a-plate tuners is 25mm (apparently too large) - Stewmac has a Golden Age set with 23.42mm spacing.(apparently too small)

dorcus_maximus · #7 01-29-2021, 08:46 AM

These are 25mm center-to-center. Definitely not 23.42mm ctc.

John Arnold · #8 01-29-2021, 11:37 AM

I have a few gears that fit on splined shafts, but no exact match to your photos. The 14:1 ratio is unusual for the time frame.
I looked at all my open Yamaha tuner sets, and the gears fit on two flats, which is the most common design.
Swapping a post can be done, but the dimensions must be exactly the same. I have modified the posts to fit in a different baseplate, or fit a different gear. It is fairly easy to turn down a post, or to file the flats to make them fit.
In most cases, I can get tuners to work, but I need to have them in hand.

dorcus_maximus · #9 01-29-2021, 01:48 PM

Quote:

Originally Posted by John Arnold

Swapping a post can be done, but the dimensions must be exactly the same. I have modified the posts to fit in a different baseplate, or fit a different gear. It is fairly easy to turn down a post, or to file the flats to make them fit.
In most cases, I can get tuners to work, but I need to have them in hand.

Yes, I was wondering about the possibility of replacing the roller and roller gear...or even if (for example) if it would be possible to swap out everything but the plate with parts from one of golden age sets from StewMac. At this point I'd entertain replacing the machines entirely if I could find a nice set that would fit.

Such a tiny part, so much trouble.

Mandobart · #10 01-29-2021, 07:46 PM

Quote:

Originally Posted by dorcus_maximus

Yes, I was wondering about the possibility of replacing the roller and roller gear...or even if (for example) if it would be possible to swap out everything but the plate with parts from one of golden age sets from StewMac. At this point I'd entertain replacing the machines entirely if I could find a nice set that would fit.

Such a tiny part, so much trouble.

The roller gear has to mesh with the worm. I think there are a few reasons why this is rarely ever done.