Sharpened at the factory, this five-piece chisel set is hand-forged from a combination of soft iron and Yasuki Shirogami (Japanese White Steel). Hollowed back reduces the friction with the workpiece. The cutting blade is tempered to HRC63+ hardness to ensure a long lived edge. The handle is made of Japanese red oak, well balanced. Please read the instructions in the box before using this chisel set. *Important Notice* 1. Do not use the grinding machine to sharpen this chisel, grinding machines may chip the cutting edge. Please use waterstone to sharpen the chisel. 2.When pulling the chisel out of the workpiece, avoid moving it front and back, wiggle it from left to right instead.