I’ve installed a lot of skylights in tar and gravel roofs. As a consequence, I’ve gummed up plenty of circular-saw blades trying to burn through the built-up roofing. Since this kind of cutting ruins the blades anyway, I decided to modify a blade so that it would work better.
I selected my dullest combination blade, and set the teeth way out — 1/4 in. or more. This radical set allowed the blade to clear itself with each revolution, and worked even better than I’d hoped.
Bob Whiteley, San Rafael, CA