Tip: Cut Holes in Foam

There has been many times I have needed to cut a smooth hole in a piece of foam. When I am building RC planes I normally want to cut a smooth hole to run a pushrod or wire through the foam. When I need to do this I don’t want to just shove a stick through the foam to create a hole, nor do I want to use a drill bit because that would just tear the foam up. What I do to cut nice, smooth holes in foam uses a brass tube.

All I do to cut a smooth hole in foam is simply choose a piece of brass tubing the size I want the hole, sharpen the end, and then rotate the brass tube while pushing it through the foam. This creates a very smooth hole. To sharpen the brass tube I use a fine file and with light pressure work around the edge of the tube till it’s nicely tapered. When filing, the end of the tube will sometimes start to curl in a little so I have to ream it out with a pipe reamer. The end of the tube doesn’t have to be sharp like knife-sharp, just not blunt. A nice taper works nicely.

With a sharpened brass tube you can straight through holes, angled through holes, foam plugs, if you start on the edge of the foam you can cut troughs in the foam, and more. It works quite well for cutting the foam. So if you’re needing to cut a smooth hole through foam, just sharpen a piece of scrap brass tubing and try it out!