On July 3, 2018 at 13:00, Ernie Gilman said...
A circular saw will indeed be quicker, but there's the danger of a rotating blade to deal with, especially on a ceiling. I say this after knowing a man who was cutting across a ceiling with a circular saw and lost quite a bit of blood when things didn't go as planned and the blade hit the arm before the blade guard swung back in place.
Also, it's easier to cut parallel edges with something slower, like a jab saw, than with a circular saw. If you have to fix non-parallel edges before you can patch, the work might take longer with a circular saw.
Since there can be PVC sprinkler pipes inside walls and above ceilings, any electric tool can be disastrous. You can feel what's happening with a jab saw.
That guy must have been cutting across his arm- I have never seen a blade guard that closed so slowly that anything could get in.
Parallel edges are easy- the distance from the blade to the edge of the guide plate is known, so screwing a straightedge to the wall that's wide enough to create the desired opening and following it with the saw makes it very clean and professional-looking. The blade depth can be set so that it will never go past the backside of the drywall, so the wiring/pipe issue is moot.
Dust collection is another story- a fine-tooth carbide blade is needed but it can be better to reverse the blade so the dust won't be pulled out as aggressively. It will also do less damage to the paper on the surface if the gullets aren't very deep, especially if the saw uses batteries and the charge level is low.
