Drilling straight holes through a template

[Nick Sorenson]

I'm trying to drill straight holes perfectly aligned through a template in wood. The template is 3/4 Baltic Birch plywood. The material being drilled is 1 3/4" Alder and Ash (electric guitar bodies). The holes need to be straight and accurate.

I'm looking for advice. Do I need a steel insert for my template?

Also, there are 3 different size holes in the string through hole in the body:

1. the main hole for the string to pass all the way through -1/8"
2. the hole for the body of the ferule (grommet) 5/16"
3. the hole for the upper rim of the grommet (3/8") so it can be flush mounted.

How would I get all 3 size holes exact with one another?

Attached are pictures of what I'm talking about in a Fender Telecaster

The next post will have just the grommet itself so you can see what I'm talking about with the flush mount.

[Nick Sorenson]

Here is the actual bushing.

[Prashun Patel]

Do you have access to a drill press? That's the easiest.

I'd use brad point bits to drill the holes from largest to smallest.

The template should be enough to guide the grommet and ferule holes vertical enough.

[Jamie Buxton]

I can't see a pic of the bushing.

If I understand what you're trying to do, I don't think a simple template is going to work. You're trying to make the 3/8" holes perfectly spaced on one face of the guitar, and the 1/8" holes on the other face perfectly space on the other face of the guitar. The guitar is 1 3/4" thick. If you drill the 1/8" holes from the 3/8" face, and if the 1/8" bit has any slight mis-angle to it, the exit holes will not be perfectly spaces. Heck, a 1/8" bit is flexible enough that it can attempt to follow grain lines inside the wood, and deflect enough to be visible on the exit face.

I'd bore from both faces of the guitar, and let the holes meet in the middle. I'd make two templates, one for each face of the guitar. One template would assure that the 1/8" holes are properly spaced where you can see them, on that face of the guitar. The other template would properly space the 3/8" holes on the other face.

[John Coloccia]

Here's how I do it:

Using the bridge as a guide, drill 1/8" holes on the back (or front....doesn't matter because the tele's flat) about 1/2 way through the body. Don't drill it all at once. Back the drill in and out to make sure the chips are really cleared out and the bit's travelling straight. If you're tele has a contoured back, then drill from the front first certainly.

Now, if you're drill press is like mine, you have a wooden insert in the middle of your table. If not, simply lay a piece of wood on top of the table. Clamp the wood down so it won't move, drill a 1/8" hole (don't go all the way through) and stick a 1/8" pin in there.

Turn the guitar over and use the pin in the table to index into the holes you previously drilled. Finish drilling the 1/8" holes.

Now you can flip the Tele over again and use the front holes to index for the enlarged grommet holes. I usually don't bother...I just line it up by eye.

Works for me at any rate. I got the idea from watching someone drill evenly spaced dowels once.....it was probably Norm

[Richard M. Wolfe]

There are drill bit jigs made for holding a hand drill for this purpose. I think one is called Accudrill. I couldn't comment on them as I have never used one. Just looking at it a problem might be 'wandering' when starting if not clamped in place. It seems to me the best way would for using one of the jigs would be to be to make a short pilot hole by hand and then use the jig. Another way might be to make a pilot by drilling the appropriate size holes in a piece of hard wood using a drill press. For drilling the project run the bit through the wood slightly, center it on the spot and clamp the 'guide' in place. The guide could be remade as needed.

[Josiah Bartlett]

Alternately you could use a plunge router for this... you would have to use a template, and clamp the body to a backer board so it doesn't blow out, and it would be best to drill the holes before you plane/sand the bottom. You will need 3 straight cutting bits of the size you need. Clamp Plunge through the 1/8" hole, then swap bits, use the same template and plunge the next size, etc. Its not as simple as a drill press but it should be very repeatable with a good template. The other option would be to modify a step drill bit with a grinder to get the size holes you want and get them all in one swell foop.

[Wes Grass]

If your template is used more than once, yes, it needs to be steel.

Could be done with a step drill, if the 1/8 section is relatively short. But because of the overall depth you'd have to pilot off the 5/16 and use a separate piloted tool for the 3/8 c'bore. Which probably isn't a standard size so that would have to be custom ground as well. May be easier to use interchangeable bushings in the fixture.

A proper fixture would align templates on both sides at once. Whether that's worth the trouble/time/cost of doing depends on your production qty's.

[Nick Sorenson]

From what I can see taking guitars apart that were made on CNC machines it looks like the hole is drilled from the back with a 3/16" counterbore, a 5/16" hole for the recess for the grommet body, a 11/64" for the main hole and finally coming out the other side with a 7/64" bit. I think the reason they do it in steps is because a 1/8" bit can flex.

So since I don't have a CNC machine, I probably need to get a metal template insert for my body template. I am thinking I probably should have the template have the largest hole in it for a 3/16" forstner bit and then use the center point from the forstner bit hole for the rest of the holes.

Any tips on lining up the drill press with the center point mark from the forstner bit?

Any idea if my template should be for the bigger or the smaller hole?
thanks,
Nick

[Doug Shepard]

...Any tips on lining up the drill press with the center point mark from the forstner bit?
....

This is rather tedious but it works. With the original forstner in the DP, lower it into the hole then clamp the work down in that location. Raise the bit and change to the smaller diameter one. Since the work is now in the way, you cant run the bit down the side to measure for setting the DP depth so you'll have to set the depth for the 2nd bit using some other method (scrap gauge blocks, digital calipers, etc) that indexes off the top surface and distance on the DP depth stop nuts. Not sure I'd want to go through all that setup for 6 holes but it works.

[Nissim Avrahami]

Any tips on lining up the drill press with the center point mark from the forstner bit?
Nick

Hi Nick

Maybe this post will give you some ideas...
http://www.sawmillcreek.org/showthread.php?t=78165

niki