Please use eye protection.
for the distinction between wafer/pin tumber locks, there is the wiki article here and how stuff works here. According the latter reference
You’re all going about opening the file cabinet the wrong way. All you need to do is lift up the lock bar that slides into side of the drawer to prevent it from opening.
Jam a wedge into the crack at the side of the drawer on the lock side. Use a flashlight to see where the lock bar is holding the drawer from opening. Insert a thin metal strip or rod (a slim jim or even a thin metal ruler works great) and lift the bar preventing the drawer from opening and pull.
Once you get it open you can remove the drawers and access the lock cylinder to replace it with a new one.
There’s also the freon and hammer trick, but canned air should also work. I’ve never done it myself but I’m sure youtube will be eager to help.
I think you turn the can upside down and spray into the keyhole. The liquid air turns the metal in the springs brittle (if it’s a pin tumbler lock). Then a sharp blow with a hammer shatters the springs. At least I think that’s the principle. No idea if this works with wafers though.
For crying out loud!
Half a pound of C-4; problem solved.
Sheesh!
I was - also ear and hand protection. I considered using a face mask, too, once the metal filings started flying, but I was working outside so I didn’t.
Anyway, the cobalt bit did the trick. I drilled all the way through the lock until I was able to rock it, and that released the drawers. I’m a little irked at the “How-to” sites for not mentioning that if you have a stainless steel lock, you’re going to need a special bit. On the plus side, I got a helluva filing cabinet for ten bucks. The thing only has two drawers, and it’s so heavy I can’t lift it. 
Thanks, all, for your help.
The problem is already solved but the best tool is with the file end of a standard nail clipper. you insert it and rotate clockwise in a rocking motion as if there is an axis in the center of the file. Usually takes about 5 seconds. Most office desk locks are like this.
Really squigs out people who forgot their keys at work and need to get into their desks. “you can open a desk in 5 seconds”.
Nuke it from orbit. It’s the only way to be sure.
Glad it worked.
It’s surprising how much difference a quality drill bit makes. Almost any bit is fine for wood, but it really takes a decent bit to drill into Stainless.
I used to be a facilities maintenance guy at a large office building and I became the “go-to” guy for people that had forgotten or lost their keys. I had (or made) master keys for most of the standard furniture brands, but if I didn’t have them on me I’d just pick the lock. My favorite was a senior VP who insisted I wouldn’t be able to open his giant wooden credenza because it was “very secure.” Well, it wasn’t. It was a typical wafer lock and I had it open in less time than it takes to read this sentence.
And I know what his face looked like when you did it. :p. A word of advice when doing this. Don’t open the drawer after picking it. Just unlock it and let them open it. It’s less traumatic/invasive for the soon-to-be-surprised person you are helping.