Drilling hole in foam rubber?

[Martin]

The rubber foam I'm working with is a very tough closed cell structure, not like styrofoam, the common urethanes, vinyls and such.

I sectioned one using a new box cutter blade, about the sharpest blade you can find these days. It was almost impossible to move it through smoothly without lubrication. A soap solution was used and I got the smooth surface I need. But with the hole saw it didn't keep the teeth from grabbing despite reversing the rotation. So I will try to sharpen some 3/4 copper pipe as I mentioned unless I can find a 1" cork borer.

You can see the texture at

[Goedjn]

Why not use 1" EMT, if what you're after is a 1" hole? Out of curiosity, what are you trying to make, anyway?

[Martin]

Used nominal 3/4" copper pipe to make the "corkborer" because it was closer to the snug fit I needed. You can see the final product at

I'm making a device called an audio coupler, usually made from metal or hard rubber. Want to see how the cellular version might work. The coupler is used between a Sound Level Meter and the source of the sound and modifies the sound so that the meter hears the sound as an ear might hear it. It's a function of the geometry of the hole. That's really an oversimplified description. There is a lot of audiometry literature on the subject, on the "2cc Coupler", 2cc referring to the volume of the adult ear canal. Picture of an earlier version being used to calibrate a headphone at