Why is it unsafe to use electric power tools that need extension cable what can you use?

Almost all my life I have used electric power tools with extension cable. I have never found it "unsafe" or ever had any incident with that. - Probably just more garbage coming from 'teachers' who think they know more than those of us who just 'do it' knowledgably and safely !

Another AnswerWell, speaking as a 'teacher', I agree that it is quite safe to use an extension cord with a power tool -in fact, that's what extension cords are for and it's probably safer than just using the limited amount of cord permanently connected to the power tool itself. There are some provisos, however; for example, if the power tool has an earth (ground) conductor then so, too, must the extension cord. And the current-carrying capacity of the power cord must equal or exceed that of the power tool. And it's best not to leave the extension cord on the reel due to the resulting increased inductance and lack of cooling. And, of course, there's the obvious safety requirements -don't drill or saw through it, or drape it is liable to become damaged or where people are liable to trip over it, etc.