Originally the can taps for R12 and 22 cans had a clip that locked over the upper lip and a neoprene sealed piece that threaded tight onto the top of the can, then a needle was threaded in to pierce the can top.

I have used the hand grip clamp type tap and it works fine. You just have to pay attention and see that you LOCK the grip as you pierce the can. I still have an old fashioned can tapper and one of the hand grips. The last time I used cans, I used the hand grip.

Good luck,