Instruct: Classify Amazon reviews into positive or negative sentiment
Query: DIY

This backer pad will not center itself on the grinder's 5/8" spindle due to its oversize mounting hole. It appears this design depends on the lock nut for centering. However, the lock nut is undersized and too small for the sanding disk's hole to allow the sanding disk to center itself. The end result is an un-centered pad and an un-centered sanding disk which result in undesired vibrations. I am returning this one and looking for another brand in hope of a more precise design.