I've only put cutting oil on two discs so far, it takes a while but it works and still feels sharp as I have to go through a good 3/8 inch of stock. No heat issues as the wheels acted like a large heatsink, I could still touch the bit after using it for a few minutes, it's just that I had to rest the drill fairly often as it wasn't very good and the bit is huge even though the shank fits a standard cartridge. Overall happy with my purchase as I've made a few wheels that have come in handy again.