Peg head hole enlargement

[Guitdrum]

I’m about to drill out the existing tuning machine holes to fit larger ones and I have a question.
Since the hole in the top of the headstock needs to fit the sleeve, I don’t have to drill all the way through right? The stem fits inside the original hole.
Secondly, if I’m using a tapered reamer you really can’t go all the way through or risk drilling a very large hole.
Do I have this right?

 

[4 Cat Slim]

The main thing is to work slowly when you use a tapered reamer, twist once or twice, then test fit the machine, and repeat until it feels right. Good luck with it!

 

[Preacher]

If you just need to make the hole for the tuner bushing larger you don't have to drill all the way through and the reamer is your best option.
Just go down far enough to get the bushing in.

You could also use a step bit and a forstner to enlarge a hole all the way through bit but it gets a little dicey and take a lot of patience to make it work. You would have to use the step bit to get to the size of hole you wanted and have around an 1/8" of depth in your piece before you switch to the forstner bit to complete drilling the hole. Again the chance of a mistake is high but it is really the only way to enlarge the hole accurately without plugging and redrilling.

 

[Guitdrum]

The main thing is to work slowly when you use a tapered reamer, twist once or twice, then test fit the machine, and repeat until it feels right. Good luck with it!

Yes thanks 4 cat for that reminder.
Care to address my other question?

 

[coloradojeff]

Stewart MacDonald (Stew Mac) has videos on this process on their website. Might be helpful

 

[4 Cat Slim]

You shouldn't have to go all the way through, just deep enough to seat the sleeve or bushing.

 

[guitarbuilder]

Most tuner bushings have splines and fit into a snug hole like string ferrules on the bridge. The casting on the tuning machine ( if it is cast) usually will require a slightly larger diameter. I usually drill through the peghead to fit the bushing and then use the tapered reamer from the back about a half turn at a time until the casting fits in with just a little pressure. If you drill through, use a piece of scrap for a backing board so the drill doesn't blow out the wood on the back.

 

[Guitdrum]

Thanks gents.

 

[awasson]

Don’t use a reamer. Get the right drill bit.

I went through this exercise last year on a Strat I was fitting vintage tuners on. I’ve got a variety of reamers, step drills, etc. but I didn’t have the correct drill size. I reamed one hole and the fit wasn’t snug. The taper was such that once it had gone deep enough the top of the hole was too wide. I went out, bought the correct size drill bit and did the others correctly. At some point I’ll refinish the neck and attend to the one hole that isn’t quite right.

 

[Nickadermis]

From stewmac just run it through from the back until the tip is flush and it's the correct size on front and back

 

[Vizcaster]

Don’t use a reamer. Get the right drill bit.

I'm sorry to disagree, but unless you're exceptionally skilled or exceptionally lucky (wouldn't we all rather be the latter?) a drill bit is not the proper tool for enlarging an existing hole. Not only can it chip the finish but because it's not being guided by anything in the center, it's possible for a flute to bind and crack the headstock (wonder how I know that?).

A step drill bit will help align with the existing hole while drilling the next step, but it won't go very deep so you need to follow with a forstner bit which is designed to guide itself from the edges instead of from the center point (there's nothing under the center because of the existing hole).

The Stew Mac step-reamer bit is sort of a single-flute drill bit with a pilot point that rides in the existing hole - perfect for the job and works very cleanly. Satisfies the canons of ethics to which we all aspire -- never remove any more wood than you absolutely have to when modifying a guitar.

But a step-drill and forstner, or the StewMac gadget, are the only ways to enlarge the front and leave the back untouched. A tapered reamer is going to be cutting the full depth of the hole, even if it's leaving a little bit more in the bottom of the hole. The advantages of the reamer are that it will not chew out the finish on the front, and you have absolute control over just how big the hole is getting until the threaded bushings of the new tuners drop into place. Besides the reamer is a very useful tool for it's intended purpose, that is to make sure holes drilled into sheet metal can be cleaned up so they come out round (ever notice how a flexible material can deform around the bit and you wind up with a hole shaped like a figure-eight? it's not an illusion). you don't need a luthier's tapered reamer that has an exact 3 degree or 5 degree taper unless you're repairing a bridge for an acoustic; the standard 1/2" tapered reamer used by mechanics and machinists will do fine for headstock modifications as well as for enlarging holes to convert imported potentiometers to domestic ones.

 

[R. Stratenstein]

View attachment 502071

From stewmac just run it through from the back until the tip is flush and it's the correct size on front and back

I'm sorry to disagree, but unless you're exceptionally skilled or exceptionally lucky (wouldn't we all rather be the latter?) a drill bit is not the proper tool for enlarging an existing hole. Not only can it chip the finish but because it's not being guided by anything in the center, it's possible for a flute to bind and crack the headstock (wonder how I know that?).

A step drill bit will help align with the existing hole while drilling the next step, but it won't go very deep so you need to follow with a forstner bit which is designed to guide itself from the edges instead of from the center point (there's nothing under the center because of the existing hole).

The Stew Mac step-reamer bit is sort of a single-flute drill bit with a pilot point that rides in the existing hole - perfect for the job and works very cleanly. Satisfies the canons of ethics to which we all aspire -- never remove any more wood than you absolutely have to when modifying a guitar.

But a step-drill and forstner, or the StewMac gadget, are the only ways to enlarge the front and leave the back untouched. A tapered reamer is going to be cutting the full depth of the hole, even if it's leaving a little bit more in the bottom of the hole. The advantages of the reamer are that it will not chew out the finish on the front, and you have absolute control over just how big the hole is getting until the threaded bushings of the new tuners drop into place. Besides the reamer is a very useful tool for it's intended purpose, that is to make sure holes drilled into sheet metal can be cleaned up so they come out round (ever notice how a flexible material can deform around the bit and you wind up with a hole shaped like a figure-eight? it's not an illusion). you don't need a luthier's tapered reamer that has an exact 3 degree or 5 degree taper unless you're repairing a bridge for an acoustic; the standard 1/2" tapered reamer used by mechanics and machinists will do fine for headstock modifications as well as for enlarging holes to convert imported potentiometers to domestic ones.

These two posts illustrate a point I was going to make: a good, sharp twist drill bit has a very good chance of grabbing, and chipping or cracking the finish around the hole, AND/OR grabbing the hole edges and uncontrollably blasting through the entire hole. The safest, “right” way to do the job is with the purpose-built tool cited in these posts. However, cost may be a factor, and most of us can get away with, and live with the job a tapered reamer, applied slowly and carefully, does.

 

[Nickadermis]

These two posts illustrate a point I was going to make: a good, sharp twist drill bit has a very good chance of grabbing, and chipping or cracking the finish around the hole, AND/OR grabbing the hole edges and uncontrollably blasting through the entire hole. The safest, “right” way to do the job is with the purpose-built tool cited in these posts. However, cost may be a factor, and most of us can get away with, and live with the job a tapered reamer, applied slowly and carefully, does.

Yes sir ! I didn't want to risk it. I do believe my bit was under twenty bucks and will be used a few times.

 

[awasson]

I'm sorry to disagree, but unless you're exceptionally skilled or exceptionally lucky (wouldn't we all rather be the latter?) a drill bit is not the proper tool for enlarging an existing hole. Not only can it chip the finish but because it's not being guided by anything in the center, it's possible for a flute to bind and crack the headstock (wonder how I know that?).

A step drill bit will help align with the existing hole while drilling the next step, but it won't go very deep so you need to follow with a forstner bit which is designed to guide itself from the edges instead of from the center point (there's nothing under the center because of the existing hole).

The Stew Mac step-reamer bit is sort of a single-flute drill bit with a pilot point that rides in the existing hole - perfect for the job and works very cleanly. Satisfies the canons of ethics to which we all aspire -- never remove any more wood than you absolutely have to when modifying a guitar.

But a step-drill and forstner, or the StewMac gadget, are the only ways to enlarge the front and leave the back untouched. A tapered reamer is going to be cutting the full depth of the hole, even if it's leaving a little bit more in the bottom of the hole. The advantages of the reamer are that it will not chew out the finish on the front, and you have absolute control over just how big the hole is getting until the threaded bushings of the new tuners drop into place. Besides the reamer is a very useful tool for it's intended purpose, that is to make sure holes drilled into sheet metal can be cleaned up so they come out round (ever notice how a flexible material can deform around the bit and you wind up with a hole shaped like a figure-eight? it's not an illusion). you don't need a luthier's tapered reamer that has an exact 3 degree or 5 degree taper unless you're repairing a bridge for an acoustic; the standard 1/2" tapered reamer used by mechanics and machinists will do fine for headstock modifications as well as for enlarging holes to convert imported potentiometers to domestic ones.

These two posts illustrate a point I was going to make: a good, sharp twist drill bit has a very good chance of grabbing, and chipping or cracking the finish around the hole, AND/OR grabbing the hole edges and uncontrollably blasting through the entire hole. The safest, “right” way to do the job is with the purpose-built tool cited in these posts. However, cost may be a factor, and most of us can get away with, and live with the job a tapered reamer, applied slowly and carefully, does.

I’m not sure how one can run into trouble enlarging a hole with the correct sized drill bit but I have respect for the work I’ve seen in the Home Depot so I’m just going to assume it’s a real danger. It isn’t going to change my approach though. I’ve got dozens of step drills and reams of different lengths and angles and my experience is a drill bit does a better job.

My most recent experience enlarging from OEM MIM tuner press in bushing to vintage split tuner press in bushings was that I will have to fix the one hole I enlarged using a strep drill and ream because the angle of the ream undercut the wood too much by the time it got to the appropriate depth. Once I saw the results, I stopped what I was doing and bought the correct size, which I think was 23/64” or something odd like that.

The other 5 were done with the appropriate sized bit. The shoulder of the bit as it comes to a point will keep the bit from bouncing and a drill press is going to be your friend for a job like that. I’m pretty handy with tools so I did mine on a bench with a big chuck cordless. There was no binding or breakage. It just worked the way it was supposed to. Had I been at all concerned, I’d use the drill press.

As I mentioned, I went for the step drill and ream first... now I have to fix it. It’s not super noticeable but I know it’s there. I would caution anyone to not make that mistake.

EDIT: That bit from Stewmac that @Nickadermis posted looks like the right tool for the job you’re doing.