Adjusting slot-head tuning machines?

[dhalbert]

I recently bought an Alvarez AP70 slot-head which has some stiff-turning and some easy-turning tuning machines. Some other owners here on AGF have just replaced theirs with Grover Sta-Tites and reported a big improvement.

But is there any adjustment that could be made on the stock ones to improve the feel somewhat? The only screw on these is the one holding the spur gear on. The worm gear post is held on by a snap washer. Would adjusting the tightness of that screw have any beneficial effect, or could I bend the worm gear end pieces slightly up or down and affect the tightness??



FOLLOWUP: tuning machines replaced; see here: http://www.acousticguitarforum.com/f...d.php?t=333862

[stanron]

Some form of lubrication between the cog and the worm and between the cog and the plate should help. As to what kind of lube I'd favour either light grease or a dry lube like graphite. I'd be interested to hear what others recommend.

[Tony Done]

Dunno, if lubricant didn't work, and I was willing to sacrifice them, I might try valve grinding paste or similar. If I did this, I would remove the tuners and clean them with solvent after treatment.

My Victor capo had a rough worm gear and I fixed it fairly well just by greasing it, and then working it under pressure for a few minutes.

[Michaelmsg]

Here is an option that worked for me on a repair that I did for a friend.

I left the tuner plates in place and removed the gear and the tuning knob. I turned the knob around so that it faced the front of the headstock and put the gear back onto the plate and tightened everything back down. The tuner actually worked much better this way. Afterwards I pulled each tuner and swapped it with the tuner on the opposite side of the headstock so that the tuner peg was actually facing the back of the headstock again.

It might be possible that all you need to do is swap the gears from one side of the headstock to the other though. I never tried that.

I do not know if this will help solve your problem but it solved the extremely sticky tuners that tended to bind and adjustaed poorly on this guitar. After this quick fix the guitar tuned perfectly without an issue.

It's worth a try. No grease and no new tuners were needed. It was as if something had been installed backwards at the factory.

Give it a shot and let us know how it turns out please.

[fazool]

By tightening the one screw on the spur gear you will affect the resistance of that gear and the tuning shaft. So, by loosening it a little, yes you can loosen the tuning machine.

But don't go so far as to make it sloppy.

The whole mechanism's action is a series of things workig in concert:

1. The worm gear turning on its axis
2. the worm gear sliding across the spur gear
3. the spur gear and shaft turning on its axis

You have no adjustment over #1 because there is no screw, only a snap washer.

You have no adjustment over #2 to account for wear so lubrication and cleaning/polishing is your only option.

You can tighten or loosen #3 and have some effect.

I would suggest disassembling, polishing the worm gear, cleaning and lightly lubricating the gear meshing, then adjusting #3.

[arie]

pull the tuners out and work them by hand. if they are smooth enough, and don't have any binding, or obvious run-out, then check to see if the posts aren't rubbing in the tuner holes. it's kinda common to see this on more modest guitars. the tuners posts run eccentric binding up in the holes, or the holes are too large allowing string pull to shift them to one side of the post hole, or the tuners are mounted off center from the post holes. posts rubbing in the hole will be identified by a shiny, burnished area on the tuner shaft or a dark and/or polished area on the inside of the post hole in the head stock.

an upgrade certainly couldn't hurt.

[dhalbert]

Thank you all. I finally had a chance to pull a tuner and see what was going on. The tuner was stiff under tension but fine when the string was slack. I changed the strings and all of the tuners became much stiffer as I got up to pitch.

There are no bushings. I think arie's explanation may be the most likely. It really does feel like the posts are binding in the holes when the string gets tight. It's hard to check for that right now as the guitar is brand new so there are no worn spots to check for yet.

Another problem was that one of the gears was actually quite loose on its splines and was slipping as I tried to tighten the string. I had to make the gear screw quite tight to fix the slipping.

So I think maybe an upgrade is in order, especially considering that other owners of this guitar have been pleased after replacing the stock tuners with 18:1 Grover Sta-Tites.