This rather dated article recommends using a shortened reciprocating saw blade to punch through drywall. I have an old blade (intended to be used to cut wood, as far as I can tell) that I'm happy to cut short for this purpose, but the page's recommendation of cutting through the blade with cable pliers is a non-starter. Perhaps recip saw blades were thinner in the 80s.
I have a decent selection of tools in the house, but not anything particularly geared toward metalworking. How can I cut through this blade to shorten it? I do have a recip saw blade that appears to be intended for cutting through metal (it has an icon of what appears to be a girder on it, and is red) but I'm not sure if another blade was the target that they had in mind for it.