DRILLING TOOL

PROBLEM TO BE SOLVED: To provide a drilling tool capable of further improving hole position accuracy and breakage resistance.SOLUTION: In a drilling tool, two cutting edges 2 are provided at a tip of a tool body 1, two spiral chip discharge grooves 3a, 3b are formed to be connected in the midway section on an outer periphery of the tool body 1, and each chip discharge groove 3a, 3b is provided in parallel from a connecting section. The total of a peripheral direction length of a margin 4 is 20% or more and 55% or less of a circumferential length of a circle of a tool diameter in a range not more than 1 times of the tool diameter in an axial direction from a tool tip. Thickness of a hard film 5 provided on a tool outer peripheral surface is 0.5 μm or more and 10 μm or less in a range not more than 1 times of the tool diameter in the axial direction from the tool tip. The hard film 5 is provided to be thicker toward the tool tip side. Web thickness W of the tool is 20% or more and 60% or less of the tool diameter.SELECTED DRAWING: Figure 2 【課題】穴位置精度及び耐折損性の更なる改善が可能な穴明け工具の提供。【解決手段】工具本体１の先端に２つの切れ刃２が設けられ、工具本体１の外周に２つの螺旋状の切り屑排出溝３ａ・３ｂが途中部で連設するように形成され、各切り屑排出溝３ａ・３ｂが連設部から並走するように設けられた穴明け工具であって、工具先端から軸方向に工具直径の１倍以下の範囲でマージン４の周方向長さの合計が工具直径の円の円周長さの２０％以上５５％以下であり、工具外周面に設けた硬質皮膜５の厚さが工具先端から軸方向に工具直径の１倍以下の範囲で０．５μｍ以上１０μｍ以下であり、硬質皮膜５は工具先端側ほど厚く設けられ、工具の心厚Ｗが工具直径の２０％以上６０％以下である。【選択図】図２