David Billington wrote:

Gunner Asch wrote:
John Doe wrote:

I have one regular and one heavy-duty "flying parts" or whatever
they are called hole cutters. The heavy duty is too big to cut a
40 mm hole. The small one probably won't cut 1/4"+ thick 6061
aluminum. I'd rather try something like this...

https://www.amazon.com/gp/product/B0...3H6VU16E&psc=1

Can you tell what sort of shank it has? I doubt square will work.
Round might work. I would prefer hex.

Any suggestions for a 40 mm aluminum hole saw, to be stuck in a
drill press?

I have a couple sets of these. What you are looking for is an Annular
Cutter:

https://www.mscdirect.com/product/details/66162819

https://www.mscdirect.com/product/de...12135?fromRR=Y

Dont bother trying to use these with a hand drill. A mill or good
solid drill press. Not! a Harbor Freight caca one either.

Ive used these to punch a hole in 1.5" 4130 plate in just a couple
minutes.

While I love annular cutters for use in the lathe and BP the 3/4" shank
may be a problem for the OPs requirements so a simple hole saw such as a
Starrett bi-metal hole saw would be more than adequate. Such as
https://www.amazon.com/HSS-BI-METAL-.../dp/B01DO4WNA8 .

Thanks. I thought carbide-tipped would be necessary, but then
figured bi-metal would work. I looked at Starrett and Morse. I
ordered two like your suggestion. One Lenox with integrated arbor,
and the other a Dewalt 7/16 inch shank arbor plus a Morse saw. Local
stores don't carry 1-9/16" diameter saws but no matter, already
delivered.