On Sat, 4 Jun 2016 10:56:08 +1000, Jon Anderson
wrote:

On 4/06/2016 12:31 AM, Ed Huntress wrote:

If it's worth the tooling investment, there are some combination bits
that will drill the hole and then ream it in one operation. Or, there
are multi-lead drill bits that drill a hole that's closer to being
round.

We have some of the multi-step single lip drills. They don't do a great
job of starting a hole in SS, but so long as material thickness is equal
or less than the step length, they do a good job. Mostly used out in the
plant though, in hand drills.

They can be useful. The combination bits I mentioned, though, are for
a single diameter, and they have a good reamer.


I'm trying to get approval to purchase a quality bench mounted punch,
something that'll do up to maybe 20mm in 2mm SS. We shouldn't be trying
to drill 20mm holes in sheetmetal...

Right. A punch is the right tool.

--
Ed Huntress