Общий каталог Yamawa 2022 - 2023 - страница 1238

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Technical Description of productsInformation Avoid scar or distortion resulting from a blow Avoid roughness surface of work piece Shank diam. Avoid burrs around the hole 26. Center Drills Center Drills are the tool for making center hole. Center Drills are also used for positioning before drilling, and for chamfering of the hole. ■Names of each part Shank portion Countersink portion Drill diam. (Dc) Drill portion (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 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 thanthat of center. Angle of center hole is lower thanthat of center. Center hole and center are misaligned. A type R type Note : R type center hole stably holds the center. It also some of advantage of B type center hole. Technical-87