Tuner Help?

[Strabo]

I recently acquired an Orpheum (Stradolin) mandolin which is structurally sound and has excellent tone. However, the tuning machines are extremely stiff. I can tune it using the business end of a plastic string winder, but I would like to have easier tuning.

Close inspection reveals that the posts lean against the inside of the hole in the headstock toward the nut enough to have chipped off a small amount of the lacquer around the edge of the hole.

The machines are unlike any that I have ever seen. The gear is steel (not brass) and appears to be brazed onto the shaft (post). There is no screw that secures the gear to the shaft -- just a blob of brass.

The gear and post are held in the plate only by a groove that is cut into the shaft and which fits into the plate. The string pulls the top of the post toward the nut and causes it to bind against the inside of the hole. This pressure also forces the gear hard against the worm. There is no bushing.

The machines turn easily when not under load, but bind against the inside of the hole when the string is pulled tight. I believe that the hard turning is caused by the post rubbing against the side of the hole and by the gear pressed hard against the worm.

Attached pictures show the partially disassembled machine and the headstock holes. I hope I uploaded these images correctly.

I see my options as follows:

I could enlarge the hole, but the design of the post and plate will still have the gear pressed hard against the worm when the string is brought to pitch. So this option seems unlikely make it turn easier.

Another option would be to install bushings. The post would lean against the bushing, and this might have less friction the current arrangement that has the post rubbing against wood.

A third option would be to replace the machines. However, the posts are spaced .087" apart. I have not found any machines that have these dimensions and do not know if they exist.

I could plug the holes and drill new ones to fit available machines, but I would prefer not to have to do this.

I'll appreciate any suggestions.

Thanks.

[dscullin]

Hello,
How are you measuring the distance between the post holes? Stewart-McDonald measures from the center of one post hole to the center of the next. Their tuners range from 0.903 inches to 0.931 inches. They have "Golden Age" tuners for vintage instruments which can be found at the URL below

http://www.stewmac.com/Hardware_and_Parts/Tuning_Machines/Mandolin/

[Strabo]

I measured from the center of one post to the center of the next -- measured three times with a dial caliper, took the average. I looked at the Stewmac tuners and was surprised to see nothing close to what I measured.

[Carl Robin]

I'd try wrapping some plumber's teflon tape around the spindle, reassemble, trim for appearance, and see if that does the trick.

[EdHanrahan]

Purely amateur opinion but, if it were mine, I'd start by cleaning 'em up and lubing with Tri-Flow, per Paul Hostetter's instructions here:
http://www.lutherie.net/tuner.maintenance.html


... The gear and post are held in the plate only by a groove that is cut into the shaft and which fits into the plate. The string pulls the top of the post toward the nut and causes it to bind against the inside of the hole. This pressure also forces the gear hard against the worm. ...

And I'd be tempted to add vintage-style bushings so that the posts have a solid surface to bear against. That should also straighten them up a bit, relieving some of the friction of those post-slots being angled against the backplate. Here's one style (the most likely?) of several that Stew-Mac offers (note the detailed blueprints):
http://www.stewmac.com/Hardware_and_Parts/Tuning_Machines/Tuner_Parts/1920s-style_Tuner_Bushings.html

(Carl's teflon tape suggestion is interesting and might help if it sticks to the wood rather than the post. But teflon is so "crushable" in pipe joints -that's what makes it effective- that I don't see it lasting as a bearing surface for very long).

[mandroid]

Solid teflon is really expensive .. It lasts just a little longer in high Heat ,

so they used in in Gaskets in the A Bombs.

[bart mcneil]

I would buy the bushings for the shaft going through the hole in the headstock, I have done this with my Strad-O-Lin as it was having similar problems. It was a while ago but I think I had to very slightly enlarge the holes in the string side of the headstock just a little for the bushings to go in to proper position. In general though I think your tuners, whatever their brand, will probably work better once this is done as long as you use some dry lubricant between the tune shaft and the newly installed bushing. On some of my old instruments I wrap a piece of sand paper around a knitting needle or similar shaft and ream out the holes until they are just a little bigger. Perhaps the wood has swollen over the years, but this does help. The bushings are cheap and they should solve your problem whatever the brand of your tuners.

[Strabo]

Thanks for your suggestions. Adding bushings is certainly a low cost approach, And metal-on-metal friction should be less than metal-on-wood, especially if the bearing surfaces are lubricated.

[mandroid]

NB: It's not like the propeller shaft of a boat ,

the only time the string capstan even turns more than Once is when you change the strings
the brass bushing (actually its like a grommet that just wont get formed into one )
should be adequate .

a dab of lube on the worm gear maybe, just before a string change,
but it got on OK for a half century before you got it.