Smooth-back knife bars carry a factory straight edge on a heavier body than thin-knife stock — 3/16″ and 1/4″ thicknesses for cutterheads whose clamping geometry wants a deeper knife section. Each 25-inch bar is cut to your machine’s knife length in-shop; one bar typically yields a full set with stock left over for the next change.
Choose the width that clears your head’s knife slot — 1-1/4″ through 2-1/2″ — in two steels: M2 HSS for everyday planing and jointing across hard and soft woods, or XLW HP where abrasive stock and longer runs justify the wear-resistant grade. Both resharpen on standard HSS grinding equipment.
