Bridge holes need to be drilled wider

I'm working on a PRS-Q1 kit and it doesn't come pre-drilled for the bridge. It's taken weeks to get the courage up to drill into this thing since I know how crucial bridge placement is to the sound of the instrument.

I was pretty sure that I saw in a video or read somewhere that a 7/16" bit was required. While at the hardware store, I brought the bridge along and tried to measure by holding the bit up to the pieces. Thought I might be OK with a 3/8" bit, so I went with that. And also because they didn't seem to have any bradpoints at 7/16". MISTAKE!

So I get home and drill out the holes only to find out that the 3/8" bit is too small. So now I have the need to widen these holes to 7/16". How? I have now acquired a 7/16" bit. However, because this is the bridge, I need these holes to be near perfectly on center. Otherwise the bridge and tailpiece won't fit right. I'm not sure I trust myself to eyeball this.

Two ideas I've had so far:

1). Fill the holes with either wood, glue, or a combination of the two. Then it's just a matter of re-measuring and redrilling. Any material added would just get drilled out anyways. Problem is I don't have spare wood really laying around so it would probably need to be all glue (Titebond II). Is that OK?

2). Measure the difference in diameter, divide by 2, mark out that far from the existing edge of the hole in 4 directions. Problem here is I don't have a caliper or know if I can precise enough without one. The smallest markings on the rulers I have now are cm. Maybe just buy a caliper?

Tell me the best way to remedy this situation!

I'd reckon the safest method would be to get some 3/8" dowel, glue them in and let them set. Then remark your centres and re-drill with the 7/16" bit. You really want something solid for the tip of the brad point to bite into, not sure the glue plug will do that for you.

Personally I think the small holes will serve to centre and align the larger drill bit. I had to do this on my Jnr as the bridge I used had larger posts than were already drilled.

Quote:

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Originally Posted by Dedman

Personally I think the small holes will serve to centre and align the larger drill bit. I had to do this on my Jnr as the bridge I used had larger posts than were already drilled.

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Yeah, Im not sure it that is going to work with the Brad Point though, the centering for it comes from the spike in the centre of the bit, if you've a smaller hole then that spike is hitting nothing and the edges of the flute are the first thing that will make contact. (At least thats how it appears on the ones I have).
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If you're using a standard drill bit then what you say is probably true, but I'd imagine that the possibility of tearing out increases if all your torque at start up is on the flutes.
I guess the best solution is to run a couple of test holes on stock and see what happens. I've not had great success with drilling out like that, but i suppose you are only talking 1/32" a side.

ah, I missed the brad point bit :P

You could just try using a standard 7/16 drill bit that's used to drill metal, I actually got pretty good results drilling holes in wood with the Titanium-coated Metal drill bits I have, I use them with a cordless drill.


To keep your drill at 90 degrees to the guitar body, you can glue two short pieces of 1 Inch by 1/2 Inch pieces of wood together to make one L-Shaped piece of wood, making sure that you get everything square.

A brad point centers the bit, you've already drilled the holes, personally I see no issue widening them by simply redrilling the new holes using the old ones as pilots, center of the hole will be the same