WhiteRook, I wish I knew.... I have a dozen or so of them that I let the idiots use. (One of them was nearly tooth-less, and that should have been a sign, but I missed it. Bit came bake with fewer teeth than the guy had.
)
Either way, the ones I have got now are lasting much longer by the simple addition of a 1/4" spring. The pilot goes through, and then you have to give it some light pressure on the spring to engage the carbide hole-saw portion.
At >$50 each they are a hard thing to spend money on, but when popping out >300 holes {FAST} in a set of panels, gutters and cans, they are money well spent. And just buy one for the job with the material, and figure if it lasts through that, its a bonus.
The only thing I know thats faster is a C-clamp for hole punches with an electric pump, and you really can only use them on everything but the back of a can or panel.