Drilling OVERLAPPING HOLES in wood: What type drill (bit) is best?

[Tom Burgess]

I'm modifying an electric guitar body made of basswood, which is considered a "soft hardwood."

I need to elongate four holes that pass through 1" of wood. They are 3/16" in diameter, and I need to convert them to 3/16 x 3/8" slots.

I would employ a 3/16" straight router bit, but cannot find one online or locally with a 1" or greater depth of cut, and budget constraints eliminate any expensive options.

Unless you can suggest a better method, I'm stuck drilling two overlapping holes next to each existing 3/16" hole, for a final slot length of 3/8". I think a Forstner bit would work, but my smallest is 1/4".

Assuming I can clamp the guitar body to my drill press table, I'm wondering if a brad point bit would hold true better than a typical twist drill.

Thanks

[Brian Tymchak]

A brad point bit works just fine for what you want to do. You must clamp your workpiece so that it doesn't shift when the spurs engage the edge of the existing hole and I like to start the 2nd hole very slowly to let the spurs do a good job sgearing the surface.

[Jamie Buxton]

To make elongated holes, I use a bit intended to go in a roto-zip tool. A roto-zip is mostly used to make cut-outs in drywall. The bit looks like a twist drill, but sides are sharpened so it can cut going sideways. I don’t have a roto-zip, but rather drive the bit with a Dremel tool.

[John K Jordan]

Just an idea. If you know someone with a suitable milling machine this is an easy task, might offer to do it for free. I've milled a lot of wood and plastic as well as metals.

JKJ

I'm modifying an electric guitar body made of basswood, which is considered a "soft hardwood."

I need to elongate four holes that pass through 1" of wood. They are 3/16" in diameter, and I need to convert them to 3/16 x 3/8" slots.

I would employ a 3/16" straight router bit, but cannot find one online or locally with a 1" or greater depth of cut, and budget constraints eliminate any expensive options.

Unless you can suggest a better method, I'm stuck drilling two overlapping holes next to each existing 3/16" hole, for a final slot length of 3/8". I think a Forstner bit would work, but my smallest is 1/4".

Assuming I can clamp the guitar body to my drill press table, I'm wondering if a brad point bit would hold true better than a typical twist drill.

Thanks

[Tom Burgess]

A brad point bit works just fine for what you want to do. You must clamp your workpiece so that it doesn't shift when the spurs engage the edge of the existing hole and I like to start the 2nd hole very slowly to let the spurs do a good job sgearing the surface.

Thanks for your helpful reply. If I go this route I will clamp the workpiece in place, and will indeed follow your advice about starting the 2nd hole slowly.

[Tom Burgess]

To make elongated holes, I use a bit intended to go in a roto-zip tool. A roto-zip is mostly used to make cut-outs in drywall. The bit looks like a twist drill, but sides are sharpened so it can cut going sideways. I don’t have a roto-zip, but rather drive the bit with a Dremel tool.

Another excellent idea. I actually do have a RotoZip tool(!) purchased years ago for a particular job and then sort of...forgotten. Duh.

THIS is advertised as a DRYWALL bit, but further down the page states, "Compatible Material: Wood, Drywall"

Do you read that to mean it can be used for wood, though it's primarily intended for drywall? I have eight holes to modify, and only need to cut 3/8" length per hole. 8 x.375" is a whopping 3 inches of cutting. Of course, it could dull in that amount of cutting IF it's intended only for drywall.

The RotoZip site, does not mention using that XB-OWD1 bit for wood, but says it has a 1/4" shank. So it would fit in my trim router's collet. The RotoZip has a minimal sheet metal ring base, a stand-off really. My router has a more substantial base (compared to the RotoZip), so does anybody know if I can run the RotoZip XB-OWD1 Outlet/Window/Door Bit in a trim router?

Thanks for reminding me about my RotoZip.

[Tom Burgess]

Just an idea. If you know someone with a suitable milling machine this is an easy task, might offer to do it for free. I've milled a lot of wood and plastic as well as metals.

JKJ

Thanks, John. In fact, I HAD a small milling machine, which I didn't use nearly enough, so I sold it in preparation for a recent cross-country move. How many times have I kicked myself for doing that...? It was a SIEG X3 purchased from Grizzly, and LOTs of accessories, too...

Ugh.

I don't know anybody with a milling machine in my new location, and can't (yet) think of a way to meet such a person. Hmmm. I'll think more about that. Thanks to all three of you for really thought provoking replies.

[Richard Coers]

You can always add a single axis, or X Y table to a drill press.

[Tom Burgess]

You can always add a single axis, or X Y table to a drill press.

Thanks, Richard. I have an X-Y vise, and could make it hold a table (of sorts) but the precision would be "relaxed" compared to my former milling machine table. And this guitar body is pretty big...

[Tom Burgess]

I'm still open to suggestions, but at this point I see a way to accomplish this.

I'll call RotoZip tomorrow to see if their 3/16" XB-OWD1 Outlet/Window/Door Bit will cut basswood that's a full 1" deep.

If not, on to Plan-B:

1. For each existing 3/16" hole, drill 2 additional overlapping 3/16" holes using a fresh brad point bit.

2. Thanks to this discussion, I discovered a 5-pack of RotoZip 1/8" SC (Sabre Cut) bits purchased back when I bought the tool (seemed like a good idea at the time...) The SC bits are intended for wood.

3. If I have skill enough, I'll use the SC bits to flatten the sides the 3-hole 'slots' made by the brad point bit.

4. Plan-B is a two-step process, which doubles my chances of messing this up. Great, another "challenge."

[Bill Dufour]

Do not use the router bit to cut full depth. Do about 1/4" deep or less per pass. I would make a rectangular guide hole in a piece of plywood or scrap for router collar. I would clamp the guide hole board to the guitar and go for it.
Hammer and chisel is always an option.
Bill D

[John K Jordan]

...I don't know anybody with a milling machine in my new location, and can't (yet) think of a way to meet such a person.

One possible way is to put your location in your user profile on SMC so it will be visible in the upper corner of every message. Someone in the same area may come to the rescue!

[Keith Westfall]

Of course, it could dull in that amount of cutting IF it's intended only for drywall.

One would think that drywall would be harder on it than wood. Wouldn't it? (never used one )

[Leigh Betsch]

How about just using a chisel

[Gordon Stump]

I would use a fostner bit and a chisel