We are scraping the black carpet pad off a hardwood floor after removing the carpet. How much do we actually have to scrap off and how much will the sander take off? I'm assuming the sander will take some off.
The sander will take all of it off. The problem you MAY incur is dependent on the composition of the padding. It will probably end up clogging your sanding disc and prevent you from getting an even sanding pattern. Or you could end up changing the sanding pads a number of times. So try to remove as much as possible before starting your sanding or sand in an out of the way spot to test.