CafeenMan

Folks keep e-mailing me asking me how I drill clean holes in balsa. I use several techniques. My first choice is a brad point drill bit but more often than not the size I need isn't available or is too large for my tiny drill press.

I've been making hole saws and punches from brass tubing for a long time. It's easy to do, but there are some tricks to making them more effective.

For example, if you use the hole saw in a drill press then you usually don't need to sharpen it much or at all. If you don't sharpen it and you use it free-hand then it will walk. If you do sharpen it and use it freehand then it will bite into the wood immediately, but the plugs are tapered and jam the saw - usually before you're all the way through.

The trick here is to sharpen the saw, but not all the way to the base of the teeth so that the teeth can shave the edges of the plug.

The basis of this is a piece of hard tubing - steel is best. Cut slots around the perimeter using a thin emery wheel. Deburr the inside and run a file around the outside. Test it on scraps and adjust as necessary.

More details here:

[link=http://www.airfieldmodels.com/information_source/how_to_articles_for_model_builders/tools/razor_hole_saw/index.htm]Make a Razor Hole Saw[/link]

RCVFR

My Feedback: (7)

Thanks for a very useful article. Not only "how to", but also pitfalls to avoid.

Dr1Driver

Great pictures, good technique.

I'd like to add: If you want the hole super clean, soak the area in thin CA first. This will harden the balsa and eliminate almost all splintering on the backside of the cut.

Dr.1

Runway

Usual, careful description. Thanks Paul.

CafeenMan

Thanks everyone. Another thought I had is to drill a hole across the tube on the opposite end of the saw to put a piece of music wire to help twist if the bit is larger.

Bumstead

My Feedback: (2)

Best balsa hole drills I found was the ones I made from a guys discarded antenna.
He had bent the tip and being kinda worried about stray electrons replaced the antenna.
Bonus from the trash pile.
I pulled the sections apart and had six various diameter drills.
With a cone shaped Dremel stone I sharpened one end of each and Bingo, six great hole saws
for free

Woodpile

Try using electrical tape to hold a new #11 Xacto blade to the outside of a hole saw of the diameter you want to cut. Extend the point to just longer than the thickness of your material and of course the sharp side must be in the line of rotation. Advance slowly with a medium bit speed and the blade will stay put and cut a perfect hole.

elcam84

My Feedback: (2)

I do something similar. I took some thin wall tubing and epoxied pieces into wood handles then sharpened the inside with a cone. Just press down and twist a little and it cuts right through. you need to sharpen it fairly often because you are using it by hand.

They are handy for cutting a hole here and there.

The antenna idea is very good as they are fairly hard. You could get bigger tubes from automatic car antennas.

CafeenMan

I normally use a punch for thin balsa, but it doesn't work in thicker wood - a hole saw works better. But the punch makes cleaner holes when it works.

Woodpile - How does the taped X-Acto blade work free hand? I'm guessing it can only be used in a drill press.

Woodpile

CafeenMan,

It's easier in a drill press because you have more control over speed and advance, but the mandrel on the hole saw keeps the blade on target. The main thing you have to watch is that the blade doesn't slip. This method cuts the cleanest holes I've ever seen in balsa though and it doesn't matter whether it's hard or soft.

Woodpile

As an after thought, you could probably use a hose clamp to get more pressure on the blade to hold it in place. A few wraps of electrical tape pulled tight works for me, but if you were cutting multiple blanks, like say wing ribs stacked together, you loose area on the blade to get a good grip.

Bumstead

My Feedback: (2)

As for me, the idea of a #11 taped to a spinning rod isn't my idea of fun

SMUGator

Agree with Dagwood.

CafeenMan

I don't think it's the safest idea in the world, but in a drill press that turns slowly and with great care, I can see that it would work very well for larger holes. What I presented is for smaller holes - maybe up to 3/4" or so if turning by hand. But for holes for wing tubes I can see at least trying Woodpile's Hole Saw of Doom.

Woodpile

Cutting holes as I described is no more dangerous than using any other power tool. Use it carefully and mind your fingers, no problems. If you're a klutz or your mind wanders, people will call you "Stumpy".

Ever take a good look at the business end of a Dremel Tool?


Ed

CafeenMan

The business end of a Dremel has often given me no choice but to look at it as it flies into my face.