same here. i have used the same blair rotobroch cutter for 3 YEARS. i am a autobody tech and have used it on 1000+ spot welds in that time.
i first drill a 1/8" pilot hole. then dip the cutter in oil and drill at about 500 rpm in my 40yo 1/2" CP air drill.
the key is SOW and use 2 hands on the drill. if the bit grabs it and twist the drill and shatter it in 3 millisecond.

and you can't use it on high strength steel.