Notes on cutting large holes with a round column mill

Other than the drilling of chip holes around the edge of the hole as you wrote above, I've also found drilling a pilot hole and using a solid pilot of that size in the hole saw to make a big difference. Less wander and squealing.
The chip holes worked wonders, but I hadn't heard of using a solid pilot. Now that I've been made aware, it seems so obvious.

I've also found that fewer teeth on a hole saw actually works better. Each tooth needs enough power to stay engaged and cut, but when you have (3tpi x 3"dia x 3.14) = 28 teeth all cutting at once the power requirements are really high. I found that after some of the carbide teeth broke off, the rest actually cut better.

Also, with carbide tooth hole saws, if a tooth breaks off, and there is no way to clear it, the bits of the tooth will embed in the metal and work to destroy every last one of the remaining teeth. The chip holes eliminated this problem.
 
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