HJC, since you asked (and Terry threw me under the bus

) here's ANOTHER thread I managed to hijack, has more pics and sources -
https://www.tractorbynet.com/forums...-table-build-6.html?highlight=mag+drill+table
However, for the project you're talking about, I agree with the other comments - there are better ways that've been mentioned.
For one thing, there may be smaller than 7/16" cutters that fit the 3/4" Weldon shank, but I haven't seen them. As Terry mentioned tho, there ARE smaller annular type cutters with regular drill shanks, that would work on your DP if you can find a way to tighten up the table tilt. Be VERY AWARE, though, that not all the sheet metal type cutters will cut deeper than 1/4" - I have this set
Blair 119 Rotobroach Cutter Kit Hole Saw Kit - Hole Saw Sets - Amazon.com
But if you look at the second picture in that link, you'll see that the smaller sizes all have a shoulder (necessary so the adapter will fit) - I just measured my 3/8" cutter, and it would just BARELY cut thru 3/8" thick steel before that shoulder hits.
Here's Blair's info -
Blair Rotabroach Hole Cutters
They don't show any cutters below 13/16" with DOC greater than 1/4", but I have their 11090 KIT
Blair 119 Rotobroach Cutter Kit Hole Saw Kit - Hole Saw Sets - Amazon.com
and I know for a FACT that the 3 larger ones have NO SHOULDER, and WILL cut 1/2" DOC. As mentioned, the smaller ones will just BARELY cut thru 3/8" material before hitting the shoulder.
That STILL doesn't help your 3/8" holes unless you stick with a 5/16" wall angle, which is made in every size from 2x3 up to 5x5 -
So, if you can get your DP tightened up and an indexing/support setup figured out, THAT seems like it'd be one of your better choices -
Then again, if you're like ME (I'm told that's not all that common, in SOME ways :laughing:0 my criteria for choices like this is "WANT" = "NEED" - doesn't ALWAYS translate to "GET"

, but not for lack of effort... Steve
Add-on - "Will a mag drill lock onto a welding table with 1/2” plate top?"
Terry covered that too; I've drilled 1/8" square tube with the drill sitting on the tube itself, but two things - one, my mag drill is "not yer father's mag drill", I intentionally bought one of the heavier duty ones, (correctly) assuming that, because it's HEAVIER, and meant to hold on vertical surfaces, that the magnet structure has more pull, and (2) I didn't push it quite as hard as I usually do.
Magnets did NOT pull loose on the 1/8" material, but my USUAL table it sits on (the GRAY thing in the pics) is a 12" long piece of 10" C channel (3/8" web) with an ADDITIONAL facing of 1/2" flat bar, full-welded, with ends closed using MORE 1/2" FB - then I surfaced the top (after knocking off most of the weld beads with a flap disk) by using a 3" diameter carbide fly cutter on the mill. This gives me a nice flat surface for the drill to grip.
I'm also planning on adding a "diving board" of 3/4x3 FB that will let me reach further out over the xy table with dual DP vises, couple jobs convinced me it was a worthwhile mod... Steve