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Idiot proof tool to enlarge a tuning key hole

Discussion in 'Luthier's Corner' started by Dan_reeves, Feb 22, 2021.

  1. Dan_reeves


    Jun 14, 2013
    I bought a bass that has 2x2 Y style tuning keys that are I believe 3/8 in diameter on the headstock. I want to swap them out for some Hipshot Lic Ultralights which I think I need to increase the hole size to either 1/2 or 5/8. I will measure to make sure once it arrives. Is there an idiot proof way to enlarge the holes? I don’t have a drill press - I do have some nice hand drills with forstner bits, etc. But what is the easiest way to do it without potentially jacking up the headstock?

    Sorry if this is the wrong place - I wanted to ask the woodworking experts. Thanks!
    EatS1stBassist likes this.
  2. Jeff Hughes

    Jeff Hughes

    May 3, 2020
    Methinks you need a peg hole reamer. There are tools just for guitars, and there are some for other applications. The stewmac ones are pricey considering you only use them every once in awhile. Go slowly and take out a little at a time. Don’t use a drill. That can have bad consequences.
    Last edited: Feb 22, 2021
  3. JeezyMcNuggles

    JeezyMcNuggles Inactive

    Feb 23, 2018
    Santa Maria, CA
    I suck, but nobody notices
    Try to fit them first. Then, use a reamer, followed by a 1/2" drill bit. The reamer will enlarge the first half of the hole, so the bit will have a less chance of catching wrong. Drill press is recommended, but if you want to just go for it, just go for it. I always do.

    You know, come to think of it, a hole saw would probably be great. Just lining up the holes right would be the only issue there. But, it'd be the safest way to pop the holes without any damage.
    Last edited: Feb 22, 2021
  4. rudy4444


    Mar 13, 2012
    Central Illinois
    Hipshot Ultralights come in two string post sizes. Make sure you have tuners in hand to verify the hole size. If the old holes are close to what you need then you can carefully sand using abrasive wrapped around a dowel that's slightly smaller than the existing hole.

    If you have the "licensed" import versions they require different holes than the regular Ultralites.

    "Licensed" Ultralites (from Hipshot's website):
    • The 3/8" diameter version fits basses with a headstock hole size of 14mm (9/16")
    • The 1/2" version fits basses with a hole size of 16mm (41/64")
    The standard Ultralites use 9/16" and 11/16" holes for the 3/8" and 1/2" string post tuners.

    Enlarging a hole in your case would depend on what tools you have available. It's also possible to slightly enlarge a hole by using a small sanding drum in a Dremel rotary hobby tool. I've used a standard twist drill in a hand held drill, but ONLY with the drill running in the REVERSE direction.
    You can also make a hardwood guide with a properly sized hole drilled in it. You clamp the guide over the hole with a undrilled block of hardwood on the back side of the hole and you can then safely use a Forstner bit that otherwise needs solid material under the center spur to guide it.

    As mentioned, a reamer can be used, but unless the reamer maximum diameter happens to be the exact size you need you end up with a tapered hole which I'm not fond of. The Hipshot tuner doesn't have a lot of wiggle room on the body side of the tuner, so if you drill a straight through hole that matches the bushing size the tuner body doesn't cover the hole by much. I'm surprised more people don't use a stepped size hole for mounting them.

    In any case, it's usually not difficult to enlarge a hole safely if a little common sense and care are exercised.
    Last edited: Feb 22, 2021
    westrock, Beej, dkelley and 1 other person like this.
  5. dwizum

    dwizum Supporting Member

    Dec 21, 2018
    If you don't know what you're doing, no matter what method you decide to try, get a piece of scrap wood, drill some holes in it, then practice making them larger. Threads like this often give me the conniptions because of how easy it is to completely ruin a valuable bass by screwing up the tuner holes. Might as well screw up a piece of scrap while you're learning.

    My personal preference for a "I don't have many tools and have no experience with this" approach would be to get a round file, trace the desired hole size on both sides of the headstock, then file the hole until it meets the lines. Plus, using a hand tool means things will happen slowly, and slow translates to "more controllable" when you're new at something.

    I would strongly suggest staying away from twist drill bits, no matter what you decide. They have a very aggressive hook angle to help them pull down into the material you're drilling. When used to enlarge an existing hole, there's no resistance against the bit - so it's easy for it to catch and yank itself into the workpiece with very bad results (cracking the headstock or tearing out a big chunk of wood). Hole saws, fostner bits, and brad point bits are a little easier to work with since they don't have a hook angle designed to pull themselves into the work, but when enlarging an existing hole, there's no way to get them started, since they all depend on a brad point or pilot bit to center them on your desired hole. If you want to go this route, either plug the holes (giving the bits something to center on) and then drill them back out to the larger size. Or, drill a hole through a piece of scrap wood, then securely clamp the scrap wood over your existing hole, such that the hole you made can act as a guide to correctly locate the bit over the existing hole.
  6. Dan_reeves


    Jun 14, 2013
    Thanks everyone for your thoughts. The bass is a Jay Turser beatle bass, so not a really expensive piece. But I would still like to do it right and get a good fit. I already have the Ultralights, and they are in fact the licensed ones not the US ones. I will measure everything first for sure to make sure the sizing is right. Maybe I’ll luck out and they’ll fit with little adjustment, but I doubt it. I am ok with woodworking but have never done this in particular so I appreciate the experienced thoughts! Thanks all!
  7. dwizum

    dwizum Supporting Member

    Dec 21, 2018
    Just to be clear - both the USA and the Licensed versions are available with either string post size. So, knowing you have Licensed doesn't imply a specific hole size is needed, you still need to verify the post size in order to know the required hole size.
    Zooberwerx, dkelley and bassdude51 like this.
  8. bholder

    bholder Affable Sociopath Supporting Member

    Sep 2, 2001
    Vestal, NY
    Received a gift from Sire* (see sig)
    Make something idiot proof and Nature simply devises a better idiot. :p

    (nothing serious to add, good luck with your tuner holes!)
  9. I second that you need to use a reamer. But if you use a drill, make sure you have a piece of wood clamped to the back of the headstock to prevent tear out.
    bolophonic, dkelley and bholder like this.
  10. Arie X

    Arie X

    Oct 19, 2015
    figure out your specs first then go buy a rat tail file (it's round) and work the holes open gradually. proceed from both ends to avoid chip out and busting up the finish if it has one on the headstock. it's low tech, cheaper than a reamer, safer then a drill, and the best path towards success for a new craftsperson then getting a drill bit caught into the wood and flinging the whole guitar into the nearest wall. it goes surprisingly faster then you'd think. smooth out the roughness with sandpaper rolled up onto a dowel or something.
    westrock likes this.
  11. Juststanley

    Juststanley Supporting Member

    Aug 11, 2014
    Yea...There is no such thing as an "idiot proof" tool !

    Go slow, measure twice, cut once....
  12. Cave Puppy

    Cave Puppy "Humph Bo, he's wond!" - John Lennon

    Jan 13, 2015
    Get you a reamer. They're cheap at Harbor Freight.
  13. r_bnks

    r_bnks Supporting Member

  14. MotorCityMinion


    Jun 15, 2017
    Tapered reamer? Ream out the holes from both sides, ever so slightly over size then drill it out. Clamp a piece of scrap to the headstock on the exit side and drill thru to it to minimize tear out.
    LostJohnny, dkelley and mikewalker like this.
  15. Allegrus


    Mar 13, 2019
    Ottawa, ON
    I'm going to give another approach even though the reamer seems a popular choice with everyone here:

    1. Plug the existing holes with a dowel or SOMETHING you can drill. I've seen someone describe this technique with using epoxy to plug the hole for example.
    2. Redrill the holes to the size you want a right-sized forstner bit. Go SLOW when you get to the end of the hole or put a backing block to minimize tear out. If your going to this by hand with a brace, it will be critical for you to be as perpendicular to the headstock when drilling as possible ... or go find a neighbour with a drill press.
  16. Dec1975


    Aug 30, 2006
    Cedar Park, TX
    A reamer would be the right tool for the job. However, in my younger years, when I didn't have a reamer, I used a step-bit from Unibit with a drill. Carefully.
    TerribleTim68 likes this.
  17. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    This is the best tool: A straight reamer with a pilot. It makes a clean counterbore of the exact size, with no splitting or chipping. I've made them up in many different sizes for different Luthier jobs. I have a couple sized just for bass tuner bushings. I normally use them in a drill press, slow speed, but they can also be turned in by hand.

    It's a simple design, easy to machine with a lathe and a mill. I usually make them from stainless steel, and don't even bother hardening them.



    I don't understand why you guys are recommending taper reamers? A taper reamer is great for enlarging holes in thin stock, but in a headstock it will cut a tapered hole. A tuner bushing needs a straight hole, a counterbore of a particular diameter and depth.

    A straight reamer, like I've shown above is the best way to cut a precise straight hole. A pilot on the front makes it easier and neater. But, you can also use a standard Machinist's Reamer of the right size.

    You can also use a large straight drill bit, gently, turning it by hand.

    If you don't have any of those tools, the safest thing is a large round file. Slowly and carefully, checking the roundness and diameter.
    Last edited: Feb 22, 2021
  18. RichterScale


    Feb 21, 2021
    This was the first thing that came to mind when reading the OP. Seeing how I have a lot of tools for general trade work and nothing specific for guitars or fine carpentry I thought, what do I have in the tool box that would work for this? The step bit is the first thing I thought of. They are typically made for metal, so would work on a harder wood. But they typically cut in shallow 1/8" increments. So, you'd have to drill to the desired diameter from both sides and then use a standard bit to drill out the center. Seems like you would have to do the same process with a reamer, since it's tapered. I think the step bit would actually work better in this particular scenario. Seeing how it would cut the wood in a straight cylinder, rather than a taper, which may help guide the drill bit better.
    I suggest getting a higher quality and more $ step bit and not the cheap ones at harbor freight though. There's definitely a difference.
    Giraffe likes this.
  19. Jazz Ad

    Jazz Ad Mi la ré sol

    Whatever you do, no brute force. You wouldn't imagine how easy it is to split a piece of wood from a tool in a see through hole.
    RikterScale likes this.
  20. step drills | McMaster-Carr

    I usually use a step drill to start the new hole. Then you finish with a regular bit.

    Scroll down to to the bottom of the page for some nice piloted drill bits. If you can find the right size, this is a good solution.

    If I order from this outfit early enough in the day, they deliver the same afternoon! No affiliation!
    FugaziBomb likes this.
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

    Mar 2, 2021

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