Funny you I should see this today as I spent a good part of yesterday sitting in the hospital with my wife and had the time to write a "Basics of Basics" on seperating welded on panels. I went thru the three common types of bits for drilling out spot welds.
That blair "mini hole saw" is actually the last one I would pick. After reading your posts I don't hate it as much as I use to though.
In certain places and times it may not be a bad choice.
But I still would HIGHLY recommend more of a "pro" type drill. I haven't seen one of those blair style in a body shop in almost 20 years!
This is more of what we use today in a shop though this particular exact design I haven't had good luck with but it gives you an idea. What we use is a one piece bit that looks like the one on the bottom of this photo with the pilot bit retracted in.
This is a lowsy photo but here is one.