Cutting round holes in thin wood

[johnpipe108]

I needed to make 11 port holes, 3/8" in diameter for the covered navigation bridge plating on the 1:24 scale submarine, in thin, soft, 1/16" basswood. I tested using a drive punch, and found that my larger, high-quality 1/2" leather drive punch could cut nice clean holes with one or two wacks from a lignum-vitae mallet. However, my cheap, utility tubular steel 3/8" punch would not penetrate, and after 6 wacks split the test piece! The edge was not good on it.

I decided to try putting it into the drill press, to use as a tube-drill. First I spun it up and touched up the edge a bit with emery cloth, then made test cuts; I ran the press at medium speed. I found that a gentle press, lift, press, lift, press, lift routine will result in a very clean circular cut in three to five "taps." This shot was taken just after cutting the eleven ports:



Tube-drills like this can be improvised for small numbers of holes, from brass hobby tubing.

HTH, John

 

[spanner570]

If I may John, and as a sort of follow on to your post, the following tip was shown to me whilst serving my time as a joiner, and could be of some use to members.....

I am sure you know the trick John, but for those who don't.....

When drilling holes of any diameter in timber or plywood, always firmly place a scrap piece of wood under the piece to be drilled. Then when you drill, go straight through your 'wanted' piece into the backing one.

This way you will always get a clean exit hole on the underside of the top piece.

I hope this will be of some use to someone!

Thanks John,

Ron

 

[CDW]

Another point worth mentioning is that the cutting edge would benefit from being bevelled from the inner diameter of the brass tube out this gives the outer diameter a clean straight cutting edge. (if the bevel's on the outside then the inner edge of the hole will crush a little due to the bevelling of the edge (sometimes though this effect is desirable)

You can use a fine round file to bevel the inner edge of the tube by putting the tube in a drill and holding the file at the required angle inside the tube untill you get the desired cutting edge.

Just a tip i picked up from a saddlemaker.