when using the angle grinder or something else that makes a huge racket it's always a good idea to use earmuffs. even if it doesn't hurt at the time it certainly doesn't do your hearing any good. also when jacking the car up make sure that the car is sitting flat on all the stands. i help out working on the aussie race cars at race meetings and some of the stuff tafe kids think is alright is amazing. one bloke thought it would be fine that the car was only resting on 3 stands and the other one was about an inch too low, lucky i was there to tell him to do it properly. another couple of kids stuffed up somehow jacking a car up in the workshop and bent the chassis.