Concrete roof tiles- tricky interview!?
I own tried many ways which cease up cracking the tile!
Answers: The best bit for cutting any concrete base product is a diamond bit. For a six inch hole, a core drill would work very economically, but it would be way too expensive. Most diamond and carborundum bit are made for circular saw which cut straight lines well but not curves. For a roof vent, you should not necessitate a perfectly verbs hole, as the roof vent will hide the hole. So basically use a masonry cutting pedals and cut a series of straight cut around the circle. This should work very resourcefully, it won't look very biddable, but when you put the metal flashing on, you won't see it.
Masory bit.
And the knowledge to use it.
You could try renting a concrete coring drill surrounded by a size that matches the vent.
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