Общий каталог Yamawa 2022 - 2023 - страница 1238

26. Center Drills Description of products Center Drills are the tool for making center hole. Center Drills are also used for positioning before drilling, and for chamfering of the hole. Shank portion Countersink portion ■Names of each part Drill diam. (Dc) Drill portion Shank diam. (Ds) Drill length (ℓ) Overall length (L) ■Shape of center hole and center Type A (60°) Center hole & 60°center Type B (60°) Center hole & 60°center Type A (90°) Center hole & 90°center Type R Center hole & 60°center ■Advantage of Type B Center holes Avoid burrs around the hole Avoid roughness surface Avoid scar or distortion resulting from a blow of work piece Note : Advantage of Type B center holes : B type center drill protect the 60° conical bearing surface from scar or distortion resulting from a blow, roughness of workpiece surface or burrs around the hole. ■Advantage of Type R Center holes Angle of center hole is higher than Angle of center hole is lower than Center hole and center are misaligned. that of center. that of center. A type R type Information Technical Note : R type center hole stably holds the center. It also some of advantage of B type center hole. Technical-87