How to drill new mounting holes?

[bhuether]

How would you go about drilling a new mounting hole for a switch? I widened a hole on one of my guitars with a typical drill bit and it caused slight cracking of the maple top around the edge of the hole. So if I drill a new hole I want it to be smooth...

Any ideas?

Thanks,

brian

[David Schwab]

Use a brad point bit.

[jrfrond]

UniBit works well also.

[tedmich]

dull the bit a ton and use a drill press, or the unibit

[stingray_65]

Making a hole larger can be a real problem.

The drill needs to be centered or it will chatter and often leave a triangular shaped hole.

The Unibit has the ability to use the step of the size hole that exists as a pilot ensuring that the bit does not randomly grab and cause the split you described.

The problem with Unibit is their lack of selection in sizes and the lack of depth of their cut. They are properly designed for sheet metal.

My solution (take it for what it is worth) isn't as simple as a Unibit, but I’ll guarantee you'll have better results.

I would glue an appropriate sized piece back in the hole that has been marked in the center and use a brad point bit to re-drill the hole.

Drills that will be used on wood where you do not want tear out will have what is called a spur on their outer lip. It cuts the perimeter of the hole before removing the center. Most brad point bits do this well.

it will leave a nice clean entrance. The back side though is where a lot of problems come when drilling wood. as the drill starts its exit it will often rip long pieces out grain wise. This can be avoided if you back up the hole to be drilled with another piece of wood. If you can’t back it up go SLOWLY as you exit and the spurs will cut its way out instead of drilling its way out

Another couple of advantages to using a brad point VS step drill

Brad points can be had in 1/32" increments allowing you to get a proper fit for the switch or pot.

By gluing the plug in and using a brad point you can actually move the center of a hole.
For example your body is routed to have mini pots and you want a full size pot, but there isn’t enough clearance by just a bit. Move half the distance of the diameter of the bit from the edge of the hole you had and the bit will drill mostly in the guitar, but no further than edge of the old hole in essence moving the center of the hole.

[stingray_65]

Now are you making a BRAND NEW HOLE?

Or just opening up an existing hole?

If you're opening up a hole now that I’m thinking about it. It probably just needs opened a fraction of an inch.

Especially if you are going from a similar sized metric to imperial size or vice versa.

This could be done quite quickly and safely with a small round file in less time than it takes to have a beer..

[David Schwab]

Now are you making a BRAND NEW HOLE?

Or just opening up an existing hole?

So if I drill a new hole I want it to be smooth...

Any ideas?

Thanks,

brian

That's why I said a brad point.

If he was making an existing hole larger, I'd say use a reamer or unibit.

I use a reamer myself.

[jrfrond]

FYI- there are UniBits that have 3/8" cutting depth.

Forstner bits are a bit pricey, but probably the best at cutting round holes, right up there with UniBits. Also, I have some single flute drill bits that I bought from a machine shop supply. They work the same as UniBits, but are single-sized.

A little-known feature that I LOVE with UniBits is that there is a slight 45° chamfer between steps, and with a little practice, you can deburr the holes you just drilled by pushing the drill slightly toward the next step size, but never actually going through. If you have access to both sides of the material, you can do it on BOTH sides, and drill darn near machine-perfect holes every time.