Hi I borrowed a wheel dresser from a friend to true up my wheel. It's a fairly old basic model that has no screw thread adjustments just an attachment that goes on the bar running across the wheel to which you slide on the square section tube which has the diamond dresser in it. When he gave it to me he pointed out the the jagged edge of the diamond saying that this is what is cutting. I've trued my stone but noticed later that the diamond tip was smooth. I looked on line and all the diamond tips I've looked at are smooth but when he lent it to me it was definitely rough feeling.. Am I just unfortunate and the tip wore out whilst I was using it or is it still good. Remember it is an old style dresser. I've added some photos. Thanks for looking Michael