Home / Standards / GB/T 6138.2-2007 GB/T 6138.2-2007 Abolished Subland twist drills for holes prior to tapping screw threads - Part 2: The types and dimensions of Subland twist drills with Morse typer shanks 攻丝前钻孔用阶梯麻花钻 第2部分：莫氏锥柄阶梯麻花钻的型式和尺寸 Standard Type GBT ICS 25.100.30 CCS J41 Status 废止 Issue Date 2007-06-25 Implementation 2007-11-01 Responsible Dept 中国机械工业联合会 Drafting Unit 中国机械工业联合会