Steel counter chamfers specially designed sleeves or counter pilot hole drilling. Adjustable depth of counter sleeve with a wrench. Woodworking drilling and chamfering removable parts. Seven pieces include bits for pilot drilling holes for screws of sizes 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 10mm. The drilling length can be adjusted for different length screws simply by loosening and tightening the screw. The chamfer is 5 grooves. During use, the wood can be unloaded faster. Smoothly drilled one-way hole. Perfect screw closure embedded in the workpiece surface. Feature: Single groove edge chamfer 90 degrees Enlarge or countersink holes, deburr edges; 15 degree bevel Use on steel, aluminum and other metals, plastic or wood Great drilling accessory for all workshop work with lifetime manufacturer's warranty Heat treated and hardened carbon steel with titanium nitrate coating for superior cutting performance Specification: Black Chamfer Drill Body Material: Steel Material: HSS 4241 Wood and