Formed GranitekSink Cut Outs

rayf01

I have this sink, and I need to knock out the knockouts to install the tape. None have been punched or drilled out yet. There is however underneith the sink, pre knockouts I guess? Where it has been partially holed, just not all the way through.

What is the best way to knock these out? Someone said a ballpeen hammer, however I think that would just crack my sink? Use a particular hole saw?

http://www.homehardware.ca/Products/..._ant_20_8x31_4

Just Bill

I would not try to knock out those precuts, but rather they should be finished drilling with a carbide or diamond hole cutter the same size, usually 1 1/8". Drill from the backside until the pilot breaks thru the top, then finish from the top.