Woodworking Mortising Chisel Sets, Square Hole Drill Bit for Mortise Machine (1/4'', 5/16'', 3/8'', 1/2'')

TAPERED SQUARE GROOVES - toolant mortise chisel bits have tapered square grooves inspired by the Japanese pattern. They help to remove chips quickly and accurately, improving efficiency compared to old-school tools with curved grooves; DUAL HEAT TREATMENT - to enhance their durability, these mortise chisel bits undergo a dual heat treatment process: 780℃ induction, 320℃ isothermal quenching, and 250℃ low-temperature tempering. This process helps to reduce quenching residual stress and brittleness while maintaining high hardness (58 ~ 64HRC) and wear resistance; HIGH COORDINATION - the core of these mortise chisel bits is straightened, and the shell goes through a three-step boring process to make sure the core and shell are perfectly coordinated; BLACK OXIDE SURFACE - our mortise chisel bits have a black oxide surface that offers top-notch anti-rust and anti-corrosion protection to the metal surface. The heating process during blackening also helps to minimize any residual stress in