I prefer the Hougen "RotaCut" cutters kit number 11075C and order an extra couple of the smallest two cutters.
I've cut hundreds and hundreds if not thousands of spotwelds with them. I would resharpen them on the belt sander occasionally. They only die when you catch one tooth to many times and break it off, but can still last a while longer missing one.
Looks like they have a size or two even smaller than the kit comes with, I may order a couple of those for the little bitty spot welds.

I've used the Blair ones, but they don't seem to last as long.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-