Suitable for industrial hinge installation, wood processing and maintenance, model making, installation of spherical door handle, drawer handle and other occasions Made of high carbon steel, special heat treatment technology, sharp knife edge, high hardness, durable, size: 15/20/25/30 / 35mm Blade arc design, cut resistance is small, improve the drill hole speed, chip removal easy, hole neat, smooth, no broken edge, will not produce tremor phenomenon