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Thread: Drill a small-diameter pilot hole, THEN a large-diameter finished hole? Or not?

  1. #31
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    Amazon has all kinds of 10 mm drill bits. I would use a 1/8" drill bit and then a 10 mm brad point bit. I have done similar many times with very good results.

    You can also get some bass wood on Amazon to practice on.

  2. #32
    Thanks for the helpful, informative replies.

    Milling machines (that weigh more than my car, ha) are not an option. I had a small SIEG X3 mill that I sold two years ago. Never thought about using it to work on guitars or other woodworking applications; kicking myself now for selling it.

    Thanks to ChrisA Edwards for the offer of basswood scrap pieces, but I'll hold off for now. There's a local woodworker's supply that might stock basswood, but as I understand it, four wood species qualify as "basswood," so your offcuts might not be the same as what was used for this particular body. Thanks a lot, though.

    I drilled through a 1" thickness that's hidden by the metal plate behind the bolt-on neck. 3/8" hole was too tight. 25/64" seems about right, though maybe slightly loose. And that brings me to the next variable:

    Better the Devil You Know: My 25/64" twist drill makes a hole that seems to work. The excellent brad-point drill by LeeValley, as suggested by Kevin Jenness, might make a slightly different sized hole, And the 10mm drill from the same source, suggested by Clint Baxter, will be a few thousandths larger. I'd like to test with both those bits, but time and money are against it.

    I've been studying up on drill geometry and sharpening. There are some significant x-factors(!) The 25/64" twist drill I have is new and sharp, and cuts a hole that feels just about right when I press the metal anchor in, so I'm inclined to use that bit. And I appreciate the point made by several of you, that a pilot hole made by a small bit might wander, so here's what I think I'll do (tell me if I'm wrong):

    1. Chuck a 1/4" transfer punch and align it's center point with my punched start hole on the workpiece.
    2. Don't move any aspect of my set up.
    3. Chuck the 25/64" drill and drill to a depth of 1", which will exit the underside of the guitar body, but in a hidden location.

    Why drill all the way through? Turns out there's only .950" of basswood thickness (less than an inch). The metal anchor is .880" long (about 7/8") and should be pressed in slightly below the surface of the guitar body. So the remaining basswood would be paper-thin, that is, IF I could do everything perfectly.

    The 25/64" hole diameter might be a tad large (loose), and while I don't find any information stating that the anchor needs a hole with a bottom surface, I think a bottom to the hole makes sense. So...I plan to screw a short length of 1/8" aluminum bar to the basswood underside, hidden from view and hopefully not interfering with the tremolo springs. The aluminum would form a flat bottom for the holes, so the anchors can't work their way down and out.

    I had no idea how many issues I'd face in "modifying" this guitar...

    =O
    Last edited by Tom Burgess; 11-28-2021 at 9:45 PM.

  3. #33
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    You are going to need a 10mm drill bit for guitar tuners anyway, so I agree with the suggestion to obtain one as well as the other common metric bits. A lot of guitar parts are metric, not Imperial so the bits like the 25/64 are somewhat an approximation.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  4. #34
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    If you can not find the correct metric drill in the configuration desired remember standard twist drills also come in number and letter sizes. All drill bits drill a hole slightly greater in diameter then the bit due to runout of the bit, chuck, drilling machine.
    I think a W drill will be closer to 10mm then 25/64
    Bill D.

    10mm= 0.393701
    W = 0.38
    25/64 =0.3906
    Last edited by Bill Dufour; 11-28-2021 at 11:37 PM.

  5. #35
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    Screw machine, screw length drill bits are shorter and less likely to wander.
    Bill D

  6. #36
    Thanks, guys.

    Stewart-Macdonald is a well-known retailer of guitar parts and tools. The Stew-Mac product page for the bridge I'm installing says, "use a 3/8" drill for the 2-point post anchors." The best how-to source I found for installing these things, member vid1900 on Stat-Talk.com, says the anchor should press in easily.

    I drilled a 3/8" hole in softwood (pine or spruce). It was difficult to press in the anchor, and the softwood cracked when the anchor was about half way in. When I drilled a 3/8" hole in a hidden spot on the basswood guitar body, the anchor felt like it wasn't going in at all. The basswood is harder (or at least more rigid) than the softwood, and I was pretty sure the basswood would crack if I forced it using the drill press as a press ram.

    Thanks to you Bill Dufour for suggesting the 'W' size drill. I didn't know it existed, but for basswood, which is prone to splitting in this case, I think the .380" diameter is too small. Slightly larger than .375", but I think still too small; that basswood won't allow much of an interference fit.

    The 25/64" twist drill makes a hole that enables pressing in the anchor "easily," requiring moderate pressure. If any problem occurs, it'll be that the 25/64" hole is slightly loose. I don't want to drill too large a hole because I don't know how to reduce it if needed (I read somewhere about wood glue and toilet paper?). But drilling too small a hole will likely crack the skimpy basswood section when pressing in, and that would destroy the guitar. So I think it's better to err on the side of a slightly large hole.

    Each anchor is fluted/splined. The outer diameter measures .392", and the lesser diameter—taken at the valleys of opposing splines—looks to be about .384". My 25/64" drill measures .387", so the sides of the wood hole will engage the anchor to about 1/2 the depth of the splines. By the seat of my pants, that sounds like a pretty good fit.

    As for metric, a 10mm drill is sure to be larger than the 25/64" drill, and that will be too large a diameter. Also, thanks Jim Becker for suggesting buying a 10mm drill for guitar work in general (and for the guitar tech user forum suggestions in your previous post). I've already replaced the Chinese tuning machines with Fender locking (staggered post heights: 3 high, 3 low) and thankfully the headstocks are drilled for 10mm tuners. Keeping the cost down is a big factor in modding these two "specimens" and I don't intend to do more of this work. So I'll hold off on buying that 10mm drill for now.

    I just need two Strats, set up differently for specific applications. The road I'm on seemed like an inexpensive solution, but the "opportunity cost" is mounting way beyond what I anticipated. Live and learn...

  7. #37
    I don't want to drill too large a hole because I don't know how to reduce it if needed

    Clearly you need to buy a cnc router in order to get the exact size hole you want.

    Seriously though, you could sleeve a slightly oversize hole with epoxy. Assuming that the posts are splined in line with their length and need to be removeable you could wax the posts before insertion. Epoxy can be softened with heat if extraction is required. If they have annular rings that is another story.

    Anticipating the exact size of a hole in wood based on the nominal dimensions of a boring bit is tricky, especially for a press fit. The accuracy of the bit's manufacture, the density and structure of the wood, runout in your drill press all contribute to the final result. Really the only way I know is to take a guess at the right size bit and try it out. Or dial it in on your cnc machine.

  8. #38
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    Quote Originally Posted by Tom Burgess View Post
    T
    I just need two Strats, set up differently for specific applications. The road I'm on seemed like an inexpensive solution, but the "opportunity cost" is mounting way beyond what I anticipated. Live and learn...
    I think that you've discovered the real life risk with inexpensive kits/components. Inconsistency, even from the same vendor. But you still get the satisfaction of setting things up the way you want.

    And don't be foolish...it will not be limited to just two S-type instruments. LOL It's like routers and hand planes...you can't have to many. Heck, I can barely play guitar and this happened...with more on the way. (The only one I didn't make is that very old, very cheap nylon acoustic)

    IMG_E0387.jpg
    --

    The most expensive tool is the one you buy "cheaply" and often...

  9. #39
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    .005” is probably very close to where you want to be for a press fit in wood. I would clamp across the grain when pressing also.
    Bumbling forward into the unknown.

  10. #40
    Quote Originally Posted by Kevin Jenness View Post
    I don't want to drill too large a hole because I don't know how to reduce it if needed
    Clearly you need to buy a cnc router in order to get the exact size hole you want.
    Ha! Count me IN!

    Quote Originally Posted by Kevin Jenness View Post
    Seriously though, you could sleeve a slightly oversize hole with epoxy. Assuming that the posts are splined in line with their length and need to be removeable you could wax the posts before insertion. Epoxy can be softened with heat if extraction is required. If they have annular rings that is another story.
    I should have included a photo of the metal anchor from the start.

    anchor.jpg

    And here's a link to the bridge in question with associated parts, including the anchors

    I'll look online for more information about lining the hole with epoxy. In the meantime, two quick questions:

    Q1. I'll be using J-B Weld (Original Formula) for the first time, to attach an aluminum brace to the interior of the guitar body - intended to support the basswood and keep it from splitting later due to vibrato bar use. The packaging describes J-B Weld as a "Cold-weld two-part epoxy system." Do you know if it would be is suitable for sleeving the hole.

    Q2. I assume the epoxy is used to lightly coat the hole. Is the idea to then redrill to intended size, with the epoxy making up the difference?

    Quote Originally Posted by Kevin Jenness View Post
    Anticipating the exact size of a hole in wood based on the nominal dimensions of a boring bit is tricky, especially for a press fit. The accuracy of the bit's manufacture, the density and structure of the wood, runout in your drill press all contribute to the final result. Really the only way I know is to take a guess at the right size bit and try it out. Or dial it in on your cnc machine.
    I appreciate your spelling that out, as it corroborates exactly where I am in the process. Sounds like the voice of experience, long-standing in your case, and recently-acquired in mine. =]

    CNC? Someday maybe.

  11. #41
    Quote Originally Posted by Jim Becker View Post
    I think that you've discovered the real life risk with inexpensive kits/components. Inconsistency, even from the same vendor. But you still get the satisfaction of setting things up the way you want.IMG_E0387.jpg
    Absolutely. Hard lessons, but as a result, I've learned more about Stratocaster guitars in the past two months than most Strat owners/players will ever know. And yeah, assuming I get everything "just right," these two strat clones will surpass some actual Fender Stratocasters costing many times the money I've invested.

    Quote Originally Posted by Jim Becker View Post
    And don't be foolish...it will not be limited to just two S-type instruments. LOL It's like routers and hand planes...you can't have to many. Heck, I can barely play guitar and this happened...with more on the way. (The only one I didn't make is that very old, very cheap nylon acoustic)IMG_E0387.jpg
    HA! I hear you, Jim. I've been down that road with other types of projects. They take over your life if you let them. Honestly, I owned one acoustic guitar for decades. That's it, just one guitar. But the ability to record digitally at very little expense opens the Pandora's Box of "needing one more instrument, or one more microphone, etc." Luckily, I proved to myself long ago that more gear seldom solves my problem. More work and practice are the solutions.

    I cannot see your photo because I'm not a supporting member at this time. I assume it's brimming with guitars in your collection, most of which you built. The ability to build inexpensive instruments that compare well with very expensive (way overpriced) big-name instruments makes it very difficult to resist building an expansive collection. Brother, there should be a 12-step program... =]

    I have two acoustic guitars, setup differently for specific purposes
    I have a short-scale, single-cutaway solid body electric with a pair of humbucker pickups (coil split) to fill the role of a Les Paul
    I have a five-string bass
    I will have one Strat clone with a floating tremolo bridge, for traditional Stratocaster work
    I will have one Strat clone with a decked tremolo (easily converted back to floating), for bending strings and imitating Telecaster tone

    THAT'S IT!
    THAT'S ALL!
    I hope... =D
    Last edited by Tom Burgess; 11-29-2021 at 4:08 PM.

  12. #42
    Quote Originally Posted by Brian Holcombe View Post
    .005” is probably very close to where you want to be for a press fit in wood. I would clamp across the grain when pressing also.
    There's some built-in inaccuracy, but I think my measurements suggest about a .005" press fit. So I take your remarks as a confirmation and encouragement (tell me if I'm wrong).

    Clamping across the grain is a great idea, but the guitar's shape makes it difficult, and being a very inexpensive specimen, the paint wants to chip off if I just look at it hard. I'll see if I can find a way. Thanks

    [AFTERTHOUGHT] I expect to install the aluminum brace described in my Post #40 above before I drill the two dreaded post holes. That brace should negate the need for cross-grain clamping.

    As your signature implies, I'm about to "bumble forward into this unknown."
    Last edited by Tom Burgess; 11-29-2021 at 1:42 PM.

  13. #43
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    Quote Originally Posted by Tom Burgess View Post
    I cannot see your photo because I'm not a supporting member at this time.
    Easily fixed...Click on the Donate button up above. $6. Well worth it as you get photos, private messages, Classifieds, etc.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  14. #44
    Quote Originally Posted by Tom Burgess View Post



    Q1. I'll be using J-B Weld (Original Formula) for the first time, to attach an aluminum brace to the interior of the guitar body - intended to support the basswood and keep it from splitting later due to vibrato bar use. The packaging describes J-B Weld as a "Cold-weld two-part epoxy system." Do you know if it would be is suitable for sleeving the hole.

    Q2. I assume the epoxy is used to lightly coat the hole. Is the idea to then redrill to intended size, with the epoxy making up the difference?.
    I don't think I'd use JB Weld for either application as it is a putty consistency and won't penetrate the wood to any degree. I use marine epoxy to wet out the wood and thicken it with various fillers when needed.

    As to sleeving, I would coat the hole with epoxy and set the pins wet. Do a test to see if it will work for you. If you can get a proper press fit by drilling that would be preferable.

  15. #45
    Quote Originally Posted by Jim Becker View Post
    Easily fixed...Click on the Donate button up above. $6. Well worth it as you get photos, private messages, Classifieds, etc.
    SIX BUX?!

    =O That's amazingly inexpensive. SawmillCreek.org has always been a great source of woodworking information, well worth supporting. And yeah, the benefits you outline are indeed worthwhile.

    Now that I'm relocated, and have decent garage space again, maybe I can return to my natural DIY ways. I sold off my bench tools prior to the interstate move, and have been working on my new/old fixer-upper house for the past year. Things are finally pretty much under control, so I WILL join as a supporting member, but will put that off until after January 1. It'll be a business expense, and I want to keep bookkeeping organized...or at least try.

    I'm trying to complete this project using only what I have on hand. Had to purchase a few specialty items for drilling in tight spaces (inside the body), but that's about all. I put together a clamping jig (out of scrap wood and a couple of carriage bolts) for mounting the guitar body on the drill press table. Man, without that, these operations are impossible. Next step is to run E and e strings from the loose bridge (set in place) to their respective tuning machines. I know you know this, Jim, but for others I'll explain that adding the strings helps me judge the space between outer strings and the edges of the fretboard. Sort of a "second opinion" to help me center the bridge relative to the neck.

    Then...gulp...it's down to marking the two actual drilling points, and going for it...

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