Earlier quoted context omitted.
It's tougher than it looks. Especially so with newer Chinese made products actually adding lead weights inside their cheap plastic cases to make their cheap products feel as though they were cut from a heavier cloth. Some rules of thumb that I have when it comes to buying old power tools are: Does it look like something your grandfather might have owned? Is it of all metal construction? If not, are the plastics of a…
Also - keep in mind a lot of places you find these things they're _really_ cheap, so it's often perfectly fine to buy one that is _probably_ good, then pull it apart when you get home to check it's interior and construction. If you only dropped $5 at a thrift store, it doesn't hurt too much when you find its actually shitty plastic with a lump of rusty steel inside - and you just trow it out...
Plenty of items that I have purchased and been unhappy with personally have found their way back to thrift stores.
I try to donate primarily to the more local actual charities that do a lot of good in my community like the salvation army, but I have no problem donating to for profit thrift stores either as I am in them often and I can see the great things that they're doing for a very large number of less wealthy people.