Drilling Sinks

I have some detergent pumps that I want to mount in the deck of two sinks. They need a 1" hole (being American). One sink is Asterite and one is Stainless.

I have a 1" HSS drill and some hole cutters.

The asterite sink has a 6mm hole that I will use as a pilot because I had a pump there before, and I think my HSS drill is the thing to use ( I can't get the hole cutters to run true on it).

I find stainless is difficult to drill because it is hard and shiny and I have an idea it work hardens. Should I drill a Pilot hole?

The stainless will snag a 1" drill and get torn up. Ideally a step drill or a hole punch is what you need, I have both and could send you one if it isn't urgent.

If it were a metal sheet you would clamp a block of wood either side and drill through that, it would hold the steel flat.

The other material I'm not sure about.

If you can't wait for a hole punch you could try geting a friend to push up against you with a block of wood, but take care you don't end up with a block of wood shaped indent.

I find that for drilling thin metal it is best to use a high drill speed hold it really firm, and if you are lucky it cuts through rather than pulling up the lip of the hole when you get to the critical point. Some form of animal fat like dripping but at least butter would help.

A Q-Max cutter is the D's B's for stainless, but I'm sure I've used a HSS/biimetal holesaw. SHould work OK for either sink, I'd have thought?

Thanks for the suggestions, and Paul, your kind offer. Am off on hols shortly, will have another think when I'm back.