I need to bore a small hole in a rubber stopper (bung) like this:
I have a set of tools called stopper-borers like these:
But I can't figure out how to use them. Simply pressing on the borer doesn't get me very far as the rubber is hard enough to resist the sharp end of the tool, but soft enough to absorb the pressure I apply and simply deform momentarily.
The tools didn't come with any instructions and I can't find any on the web. Does anyone have any experience using stopper-borers on rubber stoppers?