Our hardwood floors have been gouged and are uneven and three coats of polyurethane has already been applied on it. This is a 90 yr old home and we would like to correct the mistakes before settling in. My question: will the 3 coats of polyurethane be removed by the drum sanders? And if so what grit do we use? If this is not so, what do we use to remove the urethane before getting to the floors to even out the reckless job? Before this job was done, there was a lot of wax on the old floors and turpentine had to be used to remove the wax as the sandpaper was getting clogged up by the wax. Any help and suggestions would really be appreciated. Have a great day!