Corob Cutters machines all of their molding knives with precision CNC technology out of high speed steel blanks that are heat-treated, NOT carbide. This material is less expensive than carbide and allows you to sharpen the knives as they wear from use. To sharpen, use a few light strokes on an oil stone on the cutting face only. The unique screw/ball locking system provides a precision fit for knives each and every time. Choose from 48 shapes of molding knives to mix, match and create hundreds of custom moldings!