Feel free to add to this thread, never too late to learn something!
2 for today;
when preparing to use a hole saw, dress the set off the outside of the saw, back to where its straight down the face. You will get a much neater hole, doesn't wander near so much and actually get the diameter you wanted. While you are at it, make sure the centre drill is straight and only protrudes as much as you need (ideally thickness of the material you are drilling through IF TUBE OR SHEET. Cut in bursts of only a second r so, cut slowly and use some lubricant (WD40 at a pinch)
If you are going to try to shape alloy panels it's unbelievably easier if you anneal it (unless you are using grade zero). To anneal, scribble over the area you are going to work with a Sharpie pen (permanent type). Fire up your MAP or similar type blowtorch and warm the panel until your scribble disappears. Allow it to cool, then start work. If it becomes difficult, that's called Work Hardening, so just repeat. It might not be the technically correct method, but it works.
