I am about to buy a disc grinder for my bench grinder. I am looking at the one on Koval knives.My question is they sell 7" and 9" round sand paper that cost $3-$4 each, this seems very expensive, could I just but sheets for 75 cents each, cut out the 8" circle and use spray adhesive? I wonder if the Koval $3 sand paper will hold out much longer or not. So basically would I be better off buying sheets and making them fit my disc grinder? Thanks a lot for all the help.