Replacing the posts for Rickenbacher B8 tuners

[Mike Bonnice]

One of the tuners on my Rickenbacher B8 is bent little bit. On another the button is slightly loose. I'm sure any day now when I'm tuning, the extra torque is going to cause a button to fail. I'd like to replace the tuners before that happens.

I see on StewMac a variety of tuners that might work, they are for mandolin. I've checked their dimensions and everything matches except for the post size. On my guitar the posts measure 0.220" and the holes measure 0.23". All the tuners on StewMac use posts that measure 0.236". They will not fit in the holes in my headstock. However, maybe I can buy the mandolin tuners and replace their posts with my posts.

The tuners are four-on-a-plate geared tuners, with open gears. I don't know if they are Grover or Waverly or what. But, photos on StewMac show that the posts are attached to the gears with a screw. Maybe I can interchange my posts and screws with those of a mandolin tuner. It would require the interface between the post and the gear to match.

The attached photo shows the interface - it's a pair of flat spots on the post that mate with the opening in the gear. The width across the flat spots is 0.132" and the diameter of the round part into which the flats are cut (the shoulder?) is 0.169".

Any idea if my posts will fit the gears on the replacement tuners?

Edit: I'm assuming I'd need to keep the gears of the new part. But, maybe I can use my gears as well as posts. That would mean that the worm on the replacement tuner matches the worm on mine. Any ideas if this would work?

[Jeff Highland]

I don't know whether parts are going to be interchangeable, I don't like your chances.
Why not ream the holes in the headstock, It would only need to be 8 thousandths of an inch bigger?

[Nathan Laudenbach]

I’d be shocked if the gear thread on the post matched.

[Mike Bonnice]

Why not ream the holes in the headstock, It would only need to be 8 thousandths of an inch bigger?

In general I don't want to take material off of something that is possibly irreplaceable, in this case the neck of an eight-string Rickenbacher. I would probably want to have it done by someone skilled in reworking bakelite. Also, if I ever did find originals then the holes would be oversized.

If I'm going to take material off of something, I'll take it off of the replacement posts. I don't have a lathe to turn them down, but every challenge is an opportunity to buy a new tool.

[Matt Berg]

Jim Dulfer here on the forum supplied a replacement tuner for my prewar Ricky at a reasonable price.

[Mike Bonnice]

I replaced the tuners with new tuners from StewMac. The new tuners needed to be modified, and I used the original posts and post screws.

The tuners are Economy A-style Mandolin Tuners, Item # 0759 https://www.stewmac.com/parts-and-hardw ... nCode=0759

The modifications are these:
- Use original Rickenbacher mounting screws, posts and post screws. Use new mounting plates, gears and knobs. Ignore new bushings and mounting screws.

- Drill a new mounting hole in the mounting plate to match the original plate, enlarge two other mounting holes to 1/8 inch. Enlargement gives some play in the positioning to fit the original mounting holes in the guitar.

- Elongate the post hole in the plate for the posts that are for strings 4 and 5. The original posts for strings 1, 2 and 3 are spaced equally and are spaced like the new tuners. The spacing for the last post is larger by about 0.025 inch, so I took that material off of the post hole and off of the notch for the worm gear shaft.

This process avoids modification the guitar.

The attached photo shows the result.



In this whole process I discovered something I never noticed before. Of the eight tuning posts, three are short (about 1 inch) and five are long (about 1.1 inch). I put the three shortest ones on strings 1, 2, and 3 since the string gage is the thinnest and they don't need much post height for wrapping the string.