The woodworking drill is made of 4241 high speed steel, center bevel drill bit body is NO. Steel 45 Chamfer diameter: 15.8 mm. 4 sizes in one set of drill bits (3mm/4mm/5mm/6mm), which meet your different needs perfectly. Specially designed for sleeve cutters or pilot holes. By loosening and tightening the grub screw with a wrench (included), the depth of the counter sleeve and the drilling depth can be easily adjusted for set screws. different lengths. The drilling length can be adjusted for different screw lengths, just loosen and tighten the screws. 5-flute chamfer can unload the wood faster in the drilling process, with a smooth bore drilled at once to save you time and labor. The surface of the workpiece will be perfectly integrated with a screw cap. Compatible with drills with chuck, for drilling on hardwood or wooden floor. It is recommended to use the center punch for the position before drilling, keep the bit vertical to prevent the bit from bending or breaking.