Hi grumpy, I can see what you mean there mate, but I think the secret is that you use only light pressure, and remember that it only used to remove minor blemishes on the front edge.
My greenskeeper swears by it; if it were causing the bedknife any sort of "hollowing" anywhere, with the tolerances they use on their green mowers (to prepare their greens to championship level) I can't see them being used or purchased for that matter. Remember they are a commercial product for professionals, not necessarily for home use.....but for my money, worth every cent.
