I purchased a 4" belt/ 6" dis sander by Delta a couple of weeks ago. I was able to sand the legs to the trestle table then the sand paper on the belt started slipping. I have tighted the adjustment in both directions with no result. I have called the Delta rep, no help there either. He says there are no more adjustments that I can make. Before I return this to Lowes and buy a more expensive one would someone have any suggestions? Lorraine