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I'm in the midst of drilling a headstock for a set of Wilkinson open-backed tuners. The bushings seem to want 9mm holes.

I have some questions:

Is 9mm the common size for pressed-in bushings (like 10mm is for closed tuners)? Is a fractional size used in the US?

I read a comment that Wilkinson tuner bushings holes are 8.75 mm (right strange size) and I wonder if what I need to do is drill 8mm holes and ream larger. Any tricks to pressing bushings into tapered holes? Damfino.

Thanks!

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Peter Havriluk

It could be that since they’re a USA company they require an imperial measurement, not metric.

8.75mm is .344.5 thousands of an in, or 11/32”.

The stewmac bit I use that is designed to follow a 1/4” pilot hole for the posts cuts a .340 hole, leaving .002 to press against the very slightly tapered bushings on Grover Sta-Tites…

Thanks, Ed. I've seen 11/32 mentioned, but I didn't pay attention to the context.

I'll test with drilling 8mm and running a tapered reamer starting at the top. I've got lots of scrap to test on.

I've got a 11/32" drill bit, but it's a split point, not a brad point and it might not want to follow a punch. That's why there's testing.

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Peter Havriluk

I'll drill a pilot hole with an undersized brad point and then re-drill with the split point. The tapered reamer should work too and may give a better fit if the bushings are tapered.

Can't remember who turned me on to these but I bought them years ago for projects like this. I also bought one StewMac sells for Waverly tuners.

The ones for RC Airplane props might get you close, safely.

https://www.amazon.com/Great-Planes-Precision-Standard-Propeller/dp/B001G8VUYK/ref=sr_1_3?keywords=rc+airplane+prop+stepped+drill&qid=1707838979&sr=8-3

https://www.amazon.com/Great-Planes-Precision-Metric-Propeller/dp/B001KNGAXW/ref=sr_1_1?keywords=rc+airplane+prop+stepped+drill&qid=1707838979&sr=8-1

If a luthier supply sold them they would probably cost $100 each.

Just another handy tool in the tool box.

Using a regular twist drill to enlarge a hole can catch and pull itself into the hole and or pull up chips and be a day spoiler.

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Brian R, Wood Mechanic
N8ZED

Thanks, everybody.

Back to the shop this morning. A 't' sized drill (9.09 mm, says a conversion chart) seems to do the job with these bushings nicely. These bushings are parallel-sided and chamfered a bit at the bottom. I'll invest in some odd-numbered metric brad point drills and carry on.

I have prop reamers, and I agree that the 'luthier' markup on tools can make one gag. I've gotten more than one eyeroll when I mention that a Certain Vendor offers 'luthier'
screwdrivers, and I suspect that somewhere in their catalog is an entry for left-handed 'luthier' screwdrivers.

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Peter Havriluk

rbuddy wrote:
"Using a regular twist drill to enlarge a hole can catch and pull itself into the hole and or pull up chips and be a day spoiler. "

Hi Brian,
You are right - if the pilot hole is close to the finished size the drill can catch and pull itself through the work. A smaller pilot hole keeps the bit where it should be and doesn't usually allow this to happen.
If I am using a twist drill to "ream" a hole slightly larger then I run the drill in reverse and push the bit through -again - to avoid the drill bit pulling itself through the hole too quickly.

"Clarity" has never been one of my stronger writing traits.

Thanks Clay

I've heard of doing that before but always found a solution that seemed a little more direct. I get that if you are likely doing this once in a lifetime there is reluctance to buy specialized tools.

I thought I'd try it and see. A couple tries later into a piece of maple and my results were not stellar. I tried a couple different bit combinations but used the actual sizes required for Waverly tuners. The reversed bit didn't want to follow the hole well and did some damage the collar on the bushing might not cover.

If you are going to try reversing bit direction I would definitely do a couple test runs to check results. Always good to test new methods off the guitar anyway.

I imagine the method works better in some woods than others.

EDIT - I should add, I've had some luck doing things like this with a twist drill held in a hand drill vise or even just creating a "ball" of tape on the shank of a twist drill and spinning it by hand where you have a better feel and control of what's happening at the cutting end.

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Brian R, Wood Mechanic
N8ZED

Just an aside, I have used the SM Waverly piloted reamr for many years. I found that using a hand held drill could give a slightly oversized diameter for the bushing.
Using a drill press at low rpm worked much better. I use 250rpm.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I have 3 of the SM reamers but sometimes they don’t fit so I also have a selection of SAE and metric step drills. A sharp step drill will work well to open up holes, much cleaner than a split point bit as long as you drill a pilot hole (I use a brad point bit) that corresponds to a smaller step. A correctly-sized pilot hole stabilizes the step drill while it cuts. The step drill may not go deep enough but the pilot hole allows you to use the step drill from both sides then a split point can be used to finish the hole if needed.


Steve

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Steve Smith
"Music is what feelings sound like"

Hi Brian,
I agree it is a good idea to try whatever method you will be using on a scrap of similar material before risking the work piece, especially if you are unfamiliar with the technique. In the immortal words of Harry Callahan - "man's gotta know his limitations".
Although a press is better I free hand drilled a hole in a piece of dense tropical hardwood scrap with a 21/64ths twist drill and then reamed it with an 11/32nds twist drill run backwards. Although the grain "reversed" in the piece of wood there was little tearout when done this way with a modicum of skill, and certainly nothing the bushing wouldn't cover.
YMMV, and certainly test on scrap if you haven't done it before.

The metric brad point drills I bought from Amazon turned out to be JUNK. Dull, wobbles, immensely crude work. Returning tomorrow.

I tried a 23/64 split point drill. Beautiful fit, clean holes. I'll just have to be really careful about centering the drill bit in my center-punched impressions.

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Peter Havriluk

Amazon is turning into Ali Express. Sellers of quality merchandise are leaving the platform and being replaced by inferior products. Louis Rossman tested some 2 amp fuses bought on Amazon that took 10 amps to blow:
https://www.youtube.com/watch?v=B90_SNNbcoU

^ You know it’s sad but true…

I use the tapered plumbers reamer and ream up until the bushing fit about 3/4 to 7/8 of the way in, then use my bench vise to press them in. The vise has leather on both sides to protect the wood.

I was curious as to specs for the Wilkinson tuners. Took a while to find them but I did. I wanted to compare to Waverly's I like to use.

They are very close dimensionally but slightly different in many ways. Here are the numbers of both for anyone interested.

Wilkinson -



Waverly - edit Fixed wrong image posted earlier.

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Brian R, Wood Mechanic
N8ZED

An "F body" clamp with the soft plastic pads can also be used to press in tuner bushings. Just another way to skin that cat.

I have been using a reversed spool clamp to press on bushings for many years. I remove the finish buildup around the hole with a cut off plumbers reamer. The spool clamp works great for me.

[youtube] https://youtu.be/Pm9wlrsH5M8?si=fTUJWNKrwMrcwg7L[/youtube]

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It's not what you don't know that hurts you, it's what you do know that's wrong.