Home / Standards / GB/T 6138.1-2007 GB/T 6138.1-2007 Abolished Subland twist drills for holes prior to tapping screw threads - Part 1: The types and dimensions of subland twist drills with cylindrical shanks 攻丝前钻孔用阶梯麻花钻 第1部分：直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