The following article is taken from the AMA National Newsletter.
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CUTTING HOLES

Whenever you find it necessary to make a hole in balsa or foam (routing pushrods, antennas, etc.), the best method is to use a properly sharpened length of tubing rather than a standard drill bit which will never produce a clean, round hole in these materials. Ideally the tubing should be thin walled and available in progressive sizes for a good variety of hole sizes. Progressive sizes of brass tubing are available, work well, but can be costly.

A very good source I have found, is available in old telescopic antennas used on radio transmitters, receivers, or probably the best source, old TV set "rabbit ear" antennas. These antennas are usually long and made up of quite a few closely-sized brass tubes that can be disassembled to provide a wide variety of "drill" sizes.

Disassemble the antenna as follows:

1. Use a fine tooth saw or a Dremel tool with an abrasive cutting wheel to make a cut around the base of largest diameter tube as shown. (The tube is usually crimped onto a ball swivel or threaded mounting post.)

2. There should be one or two small, copper clips fall out when the mounting post is removed. (These clips prevent the sections from pulling apart as the antenna sections are extended and provide the electrical contacts between the sections.)

3. The copper clips retaining the smaller diameter sections together will fall out as each section is extended and collapsed. This will separate the antenna into individual tubes.

4. After all sections are disassembled, sharpen the end of each tube using a countersink bit. (This can be done by hand-rotating the bit with your fingers while holding the tube stationary in the other hand.) Be certain to sharpen the inside of the tube only. This allows the tube to cut a clean, straight hole.

When using the cutter, rotate it while pressing it against the material being cut. If possible, back up the hole on the opposite side with some scrap balsa to prevent tearing as it breaks through. If the tubing has been properly sharpened, a very accurate hole will result.

from Itasca RC Club News
33175 Gary Drive
Grand Rapids MN 55477