You can spend a lot of money on hole saws and still come out with a crude,
over size hole in sheet metal. The problem is the arbor they come with.
Too much slop.
  I found a solution if you have a lathe.
Screw in a 5/8th fine thread bolt and nut.
Turn it around and chuck the hole saw itself. Then turn the
5/8th bolt threads down to make it run true.
  Paul Lamar

I nearly broke a wrist and an ankle the other day trying to cut a 2"
diameter in the side of a 6" well casing, 6' underground (I was crammed
down into the bottom of a trench when trying to cut the hole).

I started out with a Morse hole-saw. It looked good but was a piece of
crap. I drilled a pilot hole first, then broke 5 pilot-bits trying to
get the a decent start on the 2" hole.  I finally switched to an old
somewhat dull Milwaukee hole-saw I had around and managed to get the job
mostly done.  Once I had the hole almost finished I switched back to the
much sharper Morse.  The saw jumped out of the hole, wrapped up my
shoe-laces in the drill, tried redesigning my arm so the elbow pointed
upward, and then ripped up the canvas shoe I was wearing.  That was two
weeks ago and I still have a big welt/bruise on my ankle.
I am picking up some Milwaukee blades first chance I get.  If Hilti
makes hole saws, I suspect they'd be great too.

RBerglund


Green Lee makes some decent hole saws, but turning a bolt is the way to go.

Ben Lane


I know they made punches but not hole saws. That is a good company.
I have got to order some 3/8 hex stock and weld it to the 5/8th bolt.
Most drill press chucks won't handle the hole saw torque.

I'll drill a pilot hole in the bolt and press the hex stock in before
welding.

Paul Lamar


Green-lee piloted arbors for hole saws is the professional way to go.
Don't know what you were using, but I've never had trouble with piloted
arbors. Wouldn't use anything else on NEMA cabinets. Wouldn't use a hole
saw on thin aluminum though, lots of better methods of skinning that
cat, depending on the desired diameter.
C. Smith


It is .062 5052 aluminum. The bolt trick worked well but the
1.5 inch hole is still .030" over size.

I am looking for something a bit more accurate and cheaper than
a high buck hole saw :)

Paul Lamar


Other than the fly cutter that Mr. Berglund has mentioned, I don't know
of "low-buck" solutions. I have a tapered unibit that would work. But
they are not $4 a piece. My other choice would be a punch, again, not
low dollar. Sometimes you have to spend some money to get the job done
right. For larger stuff I have a die grinder/circle cutting jig. That I
made from scrap aluminum bar stock.
C. Smith