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]