How should I fix my machine

[fatt-dad]

Greetings,

I have a 30s round-hole, flat-top kalamazoo mandoiln with basically the original tuning machines. #I know that I can replace them (correct post spacing and all), but where to find the black tuning buttons? #All that is wrong is the upper d-string tuning machine gets real hard to turn when it gets up to tension. #When the string is off the post, it turns with the best of them. #So, is the string tension pulling the string post into the wood? #Is it the string tension binding the gears? #Is it both? #What can I do to work on this (other than give up and buy another set of tuning machines).

Comments?

f-d

[Lane Pryce]

Have you tried replacing the bushings? Lp

[fatt-dad]

Have you tried replacing the bushings? #Lp
Just to be clear, are you referring to the piece of metal that inserts into the peghead hole and surrounds the string post (i.e., not a part of the machine inself)? 'Cause if that's what you're talking about, no. If you're talking about something else, no too.

f-d

[Lane Pryce]

Yup thats what I'm talking bout. Lp

[John Flynn]

Another set of machines may not actually help. As JLP pointed out, the culprit is more likely a misaligned bushing (and your definition of bushing is correct) or a nut slot that is wearing down and has started to "grab" the string. Get thee to a luthier!

[krishna]

Also 3 in 1 oil, and a Q-tip to apply oil to the gear part of the machine.This is something I do to every one of the instruments that come through my shop....Kerry

[John Flynn]

When it comes to lube, I have also used 3-in-1, but something I like better is ProTec Synthetic Gungrease. It is more viscous and more slippery than 3-in-1 and it doesn't smell. It comes in great syringe applicator that really allows you to put it right where you want it. It comes out white, but once it is worked into the gears, you can't even see it.

[Keith Miller]

I had a similar problem with an old german mandolin I cured it with graphite, good old pencil lead.
Keith.

[fatt-dad]

Machine update: I changed the strings tonight (really didn't like the FT-74s and went with the lighter gauge ghs A-250s). Here's what I notice: 1) There appears to be slack between the pinion and the screw gears; 2) The screw that holds the pinion to the string post didn't make a true connection and, 3) when the string was off of the string post, you could just drop the whole gear/post assembly down and out from the machine assembly.

I put in a washer to make a better screw fit between the pinion and the string post, but there is still movement from "vertical" when the string tension develops. Didn't notice any problems with the bushing (removed it and inspected). Gears were properly lubricated (earlier application of vasoline - I understand that this is not universally accepted by this community).

I think I need a new pinion gear and/or screw gear, which I expect will be very hard to find. So, where can I find a-style tuners with black buttons?

Comments? Did I miss something obvious?

(On the brighter side, it does tune up and sound/play nicely.)

fatt-dad

[s1m0n]

I think Frank Ford has a piece on reusing buttons by heating the shaft with a soldering iron and pulling the button off, and then putting them onto the new shaft by doing the reverse.

[Michael Lewis]

Ken Cartwright AKA Mando Medic has done all the research for black buttons. Contact him.

[Paul Hostetter]

So there are evidently two issues: 1) where to get a black button, and 2) why the gear turns harder as you get closer to pitch.

1) Are you missing a button? Is one about to go? Why are you asking? I thought you needed the gear to work.

2) the slack you describe is normal for those gears and doesn't mean a thing if all else is working right. Just only tune up to a note and you'll be OK. Which you should be doing anyway.

It gets stiffer because the string post is being pulled forward as the pitch goes up causing the worm and cog to bind. Lubrication won't help much. Correcting the alignment of the hole (not a picnic) will solve that. You must ensure the string post stays at 90 degrees with the bushing properly place, and that string tension can't pull it forward until it binds anymore. Easier said than done, but utterly do-able.

3-in-1 is gooey, terrible stuff. WD-40 is no better. ProTec or TriFlow are 1000% better, because they don't leave a residue that catches dust and then polymerizes. But your issue is not about lubrication, it's about mechanical order.

I think you can adequately save those gears. If you really want replacement gears with black buttons, they'll be like putting mag wheels on a Model A, but there are options. Schallers with glued-on ebony buttons, or better yet, Gotoh A gears with ebony buttons. The A Gotohs can be had at Allparts and thru Saga; Stew-Mac inexplicably only sells them for F-models:

http://www.stewmac.com/catalog/images_1sm/0730_1sm.jpg

They have these plates, but in a line for A model headstocks. Their buttons attach with a screw and they're really nice gears (Steve Gilchrist's gear of choice for many years). Stew-Mac sells all kinds of nice buttons for them that slip right on. They just don't sell the right gears.

[fatt-dad]

Paul,

Thanks for the throuough discussion. I was noticing that the string post does angle in the direction of the tension, but at the last few turns it also angles toward the centerline of the peghead (i.e., compensating for the slack between the pinion and the screw gears).

I have all the black buttons that I need. I was just thinking that I may want replacement machines that also have black buttons.

My machine plates are rectangular unadorned metal.

I'll see about button swapping - thanks for the tip through Mr. Ford.

fatt-dad

[WireBoy]

i recently did a 'repair on a tuning gear/worm. #it was very hard to turn, even removed from the instrument. #a closer inspection revealed the worm was jammed too close to the gear. #the gear teeth were binding on the worm as the would enter and exit the worm. #i disassembled the gear from the tuner, got a needle file and reshaped the gear teeth so they would mesh better with the worm. #it was tedious, but it worked.

[fatt-dad]

i disassembled the gear from the tuner, got a needle file and reshaped the gear teeth so they would mesh better with the worm. #it was tedious, but it worked.
I would do that if I knew what my backup plan was.

[Paul Hostetter]

Swapping the old black buttons will only work if the shafts on the old and new sets are identical.

You say "it also angles toward the centerline of the peghead (i.e., compensating for the slack between the pinion and the screw gears)." I'm not sure anything is compensating, but what's happening is another artifact of a badly aligned string post relative to the plate and the geometry of the headstock. I assume these tuners all have bushings in the holes on the face of the headstock, yes? Get the bushing planted firmly where it belongs, which may well entail filling and redrilling the hole, and the rest should be taken care of.

One more thing: your gear works well when not under load. Don't file any metal in your gears!!

[fatt-dad]

ITEM 1. . .another artifact of a badly aligned string post relative to the plate and the geometry of the headstock.

ITEM 2. . .I assume these tuners all have bushings in the holes on the face of the headstock, yes?

ITEM 3. . .Get the bushing planted firmly where it belongs, which may well entail filling and redrilling the hole, and the rest should be taken care of.

ITEM 4. . .One more thing: your gear works well when not under load. Don't file any metal in your gears!!
Paul H. Thanks for the discussion! Comments on four items:

Item 1 - So what can be done about that (I think this is a major factor)

Item 2 - All bushings are in place and flush with the face off the peghead. On the errant tuning machine, I removed the bushing and there were no sighs of wear on the inside of the bushing (for what that's worth).

Item 3 - Not clear how to "get the bushing planted where it belongs" Would love to know how to figure that out. . .

Item 4 - The maching turns just fine when not under load. As an engineer (O.K. so I'm not a mechanical engineer, but I understand the thought process) I can "see" how the string tension is pulling the string post into "something" and creating the added friction. There is a part of me that still wants to blame the gears, the gear-to-string-post connection or the string-post-to-the-base-plate relationship.

The good news remains that the mandolin tunes up and plays. If I knew what to expect, I would be willing to ship it off for a proper evaluation. However, if it is hopeless, I have no problem changing the machines (other than I would like to keep the black buttons).

Whew!

f-d

[Paul Hostetter]

Item 1 - Fill it and start over.

Item 2 - The hole is in the wrong location or orientation, ergo the bushing is too. Bushings usually don't wear, but if the hole is misaligned, or even became misaligned, it takes the bushing with it. Even being 2 degrees off is enough to allow the string post to lean forward and not work.

Item 3 - Use the precise measurement of the plate holes as a guide. A drill press is essential for redrilling hole. If the hole is perfectly aligned with the plate, and the bushing is firmly situated to preserve that 90°, the post can’t pull forward under load. Anyone who has had to retrofit new gears to old Gibsons has probably encountered this. They really look like they’ll fit, but that tiny smidge of difference in post spacing is deadly, and is usually felt in the end posts which are more played or crunched in. Gibson made three different post spacings, each almost imperceptibly different. But different enough. And I digress. The point is, it takes very little misalignment to make for a very noticeable malfunction of the gear when under load. 1/32".

Item 4 - The plate is a bearing for one end of the string post, the end that also has the cog. The string post requires two bearings to keep it at 90° - and the other one is the bushing at the end of the hole at the face of the headstock. You can all kinds of slop in the system as long as the post is held firmly at 90° when it is under load. When it can pull forward, the binding that’s occurring is at the plate and the cog side of the plate. No amount of lubrication will help, you have to tilt the post back to 90° so the cog’s not binding on the worm, and make sure it stays there. The fact that the machine turns just fine when not under load is evidence of that.

Changing the machines is not necessarily a foolproof solution - if the holes aren’t quite right (and it’s easy to be fooled by appearance) you may well have to go the same process making new ones work. I’d give the existing ones a bit more effort before giving up. Maybe you need help with this? I have sure done it a bunch.

[fatt-dad]

Thanks All! I am otherwise on Spring Break and will have to table this project for a week.

f-d