Hi George, although the bearing system in a drill is designed to take end thrust in the main the lower bearing / bush will also keep the drill bit running true and stop it spiraling out of control. The amount of pressure normally applied to a drum sander will not have any adverse effect on your drill spindle. The more accurate the bobbin runs the better not only to put less stress on the quill but makes shaping easier. You might be better off looking at the Axminster Large drum sander for your drill.
Mike
