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Thread: Worm under, Worm over? A visual guide.

  1. #1
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    Default Worm under, Worm over? A visual guide.

    This may have been discussed on the Cafe before but there still is some confusion about identifying the so-called “worm over” and “worm under” style of tuners. “Worm under” tuners have the worm closest to the string nut.

    I created this simple visual guide as a supplement to Paul Hosteler’s (rip) excellent tutorial.

    http://www.lutherie.net/mandolin.gear.direction.html

    The visuals only allow you to identify at a glance which type you have, it does not address other variances such as the post spacing, post diameter or gear ratio. With this guide you’ll be able to tell quickly wether those orphan or new tuners are the right type for your instrument.

    Notice that the “worm under” type have a right-hand threaded worm. A right hand thread is the common type when we think righty tightly, lefty lucy in our every day world and having nothing to do with mandolins. The “worm over” type have a left-hand threaded worm. As Paul explains this was done so that the tuner knob turns in the same direction as the “worm under” type. The left-hand worm may have been the genesis of the use of “reverse thread” or probably later “reverse tuner” again having nothing to do with the tuner knob being turned in reverse, this is not the case.

    For you terminology buffs here is the meaning of right hand or left hand threads and an exercise.
    Hold your right thumb out and curl you fingers around as if you were hitch hiking in the US, now point you thumb away from you. The thread will cause the shaft to move in the direction your thumb is pointed when turned in the direction your fingers are curled. This makes it a right hand thread. Now try it with your left hand. Easy, right?

    With Gibson the change from worm under to worm over tuners seems to have occurred somewhere during 1925.

    I hope some of you find this useful.

    Mark

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    Last edited by MarkELynch; Mar-31-2021 at 1:03pm.
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    Default Re: Worm under, Worm over? A visual guide.

    Thanks so much for doing this! It's a big help. Might not be the most mysterious mystery concerning these merry little music makers, but with multitudes of murky misinformation motes mucking up understanding, every bit of minutiae, however seemingly minor, helps.

    To that end, here is an example of a worm-under configuration in place, on a 1916 A-4 mandolin.

    Click image for larger version. 

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    Question Re: Worm under, Worm over? A visual guide, Again?

    Worm Gear Cut is either: \\\\ vs ////.. ... //// works as worm over .. where \\\\ works as worm under ..

    To Increase Pitch, your knobs still turn CCW .. (as if a violin peg, but with a gear ratio advantage)
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    Default Re: Worm under, Worm over? A visual guide.

    I never heard worm under/worm over before hearing it on this forum......I find those terms confusing.

    Although not entirely correct, I think of tuners as being "normal" or "upside down" -- such as bowlbacks, etc. usually have upside down tuners, for example.

    or possibly "modern style" vs "old style"

    The problem being, "do they turn the right way?"

    One of the many quirks of our hobby, especially when it comes to vintage instruments.

    Another (unrelated) challenge for the repairman is when a left-handed customer wants an electric guitar with control pots that turn "counterclockwise" when going from 0-10.........

    all in a day's work

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    Default Re: Worm under, Worm over? A visual guide.

    Well-l-l ... Terms such as "normal" or "upside down" indicate or at least imply a bias, in that one way is correct and the other ... not so much. I have no idea why one way would be thus and the other the other, nor why Gibson would decide to make a change, all other aspects being acceptable. "Worm under" and "worm over" are simple descriptions of observable configurations, so preferable, IMO. What I do appreciate is the explanation of how both set-ups retain the direction in which one turns the tuning peg to achieve the same result: the direction of the worms is reversed to accommodate the configuration. That had never occurred to me. 'Tis brilliant in its simplicity and simple in its brilliance. Genius is often thus.
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    Default Re: Worm under, Worm over? A visual guide.

    Thanks for the nice feedback and Mandroid, that is a great shortcut (/// or \\\) if you can’t spot a right hand or left hand worm easily.

    Now, it is possible to mount tuners upside down, by that I mean you could mount worm over tuners as if they were worm under tuners. So describing them as an upside down type of tuners will only lead to more confusion.

    In some examples when the tuner is mounted upside down the posts and mounting holes align exactly as is the case with this Gibson Style U Harp Guitar in my collection. It came to me with a set of 30’s Waverly worm over tuners of the type used on a Gibson L-00 guitar. The problem, you guessed it, is that the knobs need to be tuned in reverse. They work fine mechanically but tuning is confusing because it doesn’t follow the convention. Sorry the photo is not that clear, the red line shows the left hand worm thread, (the line has a negative slope if you recall your HS geometry). Remember, worm under tuners need a right hand worm thread. I have since located the correct tuners for the Harp Guitar.

    Click image for larger version. 

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    Mark
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    Default Re: Worm under, Worm over? A visual guide.

    Quote Originally Posted by journeybear View Post
    I have no idea why one way would be thus and the other the other, nor why Gibson would decide to make a change, all other aspects being acceptable.
    I'm not sure if it was Gibson who made the change, but I have always read that physics-wise, the string under tension pulls the gear into the worm on worm over tuners and thus is more stable, whereas on worm under tuners the gear is pulled away from the worm, however slight, which could result in tuning issues.

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    Default Re: Worm under, Worm over? A visual guide.

    Quote Originally Posted by Jeff Mando View Post
    I'm not sure if it was Gibson who made the change, but I have always read that physics-wise, the string under tension pulls the gear into the worm on worm over tuners and thus is more stable, whereas on worm under tuners the gear is pulled away from the worm, however slight, which could result in tuning issues.
    Or a tuner that doesn't bind and turns easier?
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    Default Re: Worm under, Worm over? A visual guide.

    Yes, these things are described in Paul Hosteler’s webpage listed in the start of this thread.

    http://www.lutherie.net/mandolin.gear.direction.html

    The theory that the meshing of the worm and cog are affected less when the worm is above versus below has some merit. However, if the tuner shaft is properly supported by a well fitted bushing in the headstock and since the bearing point of the shaft in the tuner plate is so close to the meshing point of the gears the difference in operation should be negligible.

    Has anyone here done any experiments to compare the two types? I have plenty of instruments representing both types, some vintage and some modern and have never felt a discernible difference. I’m curious about your findings.
    Last edited by MarkELynch; Apr-02-2021 at 9:14am.
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    Default Re: Worm under, Worm over? A visual guide.

    I think the main reason worm-over is the common setup is it offers more room for left hand when playing in the low frets. It moves the tuner button farther away, while keeping peg shafts as close as possible to minimize the string length beyond the nut, making the tuners more responsive.
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    Default Re: Worm under, Worm over? A visual guide.

    Tom, that is a fabulous observation, I was focused on the mechanics and not on the playing application! Your comments caused me to pull two A4’s from the collection and make some measurements. Did anyone ever hear the old saying that one measurement is worth a thousand armchair opinions? (No offense intended to you, Tom, you probably made your own measurements already!) Here is what I found. Indeed, as Tom says, there is more hand clearance above the nut! Has this been an issue? In these examples, while the string length between nut and string post is shorter the difference is small. Less that a quarter inch in this example. Maybe it is more extreme in other applications.

    Here are some photos of a 1915 A4 with worm under tuners and a 1931 A4 with worm over tuners.

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    1915 A4 below:

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    1931 A4 below:
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    Side by side, 1931 left, 1915 right, note the extra hand clearance above the nut that Tom describes:
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    Note, the caliper is measuring in inches.

    I hope you find this exercise useful. I haven’t compared the F models but suspect we’d find a similar result.

    Mark
    Last edited by MarkELynch; Apr-02-2021 at 12:04pm.
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    Default Re: Worm under, Worm over? A visual guide.

    One may think, well, all of not even a quarter inch of a difference, big deal. In mandolin terms, a quarter inch is as good as a mile. (Now there's a paraphrase gone wrong!) The scale of the instrument is such that minute measurements make enormous differences. Consider how much is made of nut widths, for example - 1/8", even 1/16", gets a lot of consideration. Such matters may seem minuscule, but they do affect playing in no small measure. Pun most definitely intended.
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    Default Re: Worm under, Worm over? A visual guide.

    Okay, now that you guys are all experts on this tuner stuff, here is a test! :<)

    What is wrong with this photo?

    Click image for larger version. 

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    Default Re: Worm under, Worm over? A visual guide.

    Well there is an ear missing on the top of each tuner plate, but what I think you are looking for is the fact the worms are both the same direction on both plates, but they will need to turn backwards.
    Last edited by pops1; Apr-10-2021 at 11:29am.
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    Default Re: Worm under, Worm over? A visual guide.

    The worm gears are in the opposite direction of the 1931 in Post #11.

    And it's not a Gibson.
    But that's just my opinion. I could be wrong. - Dennis Miller

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    Default Re: Worm under, Worm over? A visual guide.

    Well, you two have studied your homework! The tuners are mounted upside-down on overly reworked Gibson A-Jr currently listed for sale.

    Yes, the A style tuners on the A-Jr have a right handed worm and are intended to be mounted with the worm under the driven gear.
    You both identified that the knobs needed to be turned backwards but will have to share the first prize. A free and lifetime subscription to the Mandolin Cafe member’s Forum.

    In the Schaller GrandTune advertising literature I notice the term “reverse gear”. This is confusing but I’m convinced that the term came about in reference to the left-hand worm gear thread. Common screw fasteners and all right-handed as are the worm under tuners. The left hand threads and worms could be considered “reversed” even though the knobs turn the same way in both worm under and worm over tuners.

    Just my observation and opinion, of course. I think we all have our own ways of identifying the tuner types.

    Mark

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    Default Re: Worm under, Worm over? A visual guide.

    Okay, this test is more difficult.

    What is wrong with this photo?

    Click image for larger version. 

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    Default Re: Worm under, Worm over? A visual guide.

    Mandolins have eight strings, not four. Do I win?

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    Default Re: Worm under, Worm over? A visual guide.

    The mandolin is missing!
    But that's just my opinion. I could be wrong. - Dennis Miller

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    Default Re: Worm under, Worm over? A visual guide.

    Quote Originally Posted by MarkELynch View Post
    Okay, this test is more difficult.

    What is wrong with this photo?

    Click image for larger version. 

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    The tuner is supposed to be "worm under" but the gear is cut with left haded worm so they will turn opposite to normal direction. But this tuner cannot be disassembled so a dud.
    Schallers nomenclature can be very misleading to buyers and often their own attempts are confusing especially when buying through US sellers or guitar shops who don't know a thing about mandolins.
    I once got tuners just like this when I ordered the "worm under" (they call it reverse, but many US vendors call reverse the worm over tuners) but the olde Schallers could be re-assembled to proper "worm over" and later I used it that way. With the new GT's you should make sure they're sending you the correct version...
    Adrian

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  27. #21
    Adrian Minarovic
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    Default Re: Worm under, Worm over? A visual guide.

    Here is big quiz.... pics from Rubner website... https://www.rubnertuners.com/f-style-mandolin-new
    Which of these are wrong?
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    Default Re: Worm under, Worm over? A visual guide.

    Supposedly Rubner's are great tuners, but visually I can't get past the black knob shafts. Looks ugly (and cheap) to me, which I'm sure was not their intention.

    Like 30-35 years ago when Mercedes started using grey plastic filler panels beside the grille, headlight and bumper areas that had been previously chrome, stainless steel, or painted metal -- really cheapened the appearance, IMHO. And yes, we've all gotten used to it, but still......ugly!

  30. #23

    Default Re: Worm under, Worm over? A visual guide.

    Worm over it is. 1925 A4.

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    Default Re: Worm under, Worm over? A visual guide.

    MM,

    Your 1925 A4 is correct, it has a left hand worm and worm over configuration.
    It will tune up in the normal CCW direction from the button’s perspective.
    From this example and Adrian’s many example in his quiz above we can see that both the worm type(left or right handed spiral) and the worm position (above or below) affect which way the button is turned.

    The worm position and worm type change for Gibson seems to have occurred in or about 1925, some companies did it later.
    I have a 1931 National Style 1 with right handed, worm under tuners.

    Mark
    Last edited by MarkELynch; Apr-16-2021 at 11:41am.
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    Default Re: Worm under, Worm over? A visual guide.

    Thanks for posting this Adrian, I’ll take a stab at your quiz. It’s hard to see the worm teeth in a few so forgive my eyesight!
    Based on the shaft lengths I believe these are all intended to be F-style worm under tuners since the long shaft needs to be at the top of the instrument.

    Here are the options that determine which direction the tuner knob is turned to change the pitch.

    Worm Type: Right-Handed spiral or Left-Handed spiral.
    Worm Position: Below the cog or Above the cog.

    This means there are four combinations.

    A. Right Hand worm Spiral and Worm Below: turn CCW to raise pitch (normal)
    B. Left Hand worm Spiral and worm Above: turn CCW to raise pitch (normal)

    C. Right Hand worm Spiral and worm Above: turn CW to raise pitch (so called reverse tuning in some specs)
    D. Left Hand worm Spiral and worm Below: turn CW to raise pitch (so called reverse tuning in some specs)

    Clockwise, CW or Counterclockwise, CCW, is from the button’s perspective. Sorry, Anticlockwise in some parts of the world!

    if I’ve identified the worms correctly in the photos I believe that numbers 2, 4 and 7 tune in the CW direction or opposite the normal way.

    I’ll await your “grade”.

    Best Regards,
    Mark




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    Mark Lynch

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