GB/T 39542.3-2020技术制图活动铅笔第3部分:黑铅芯HB铅芯弯曲强度标准
英文:Mechanical pencils for technical drawings—Part 3: Black leads—Bending strengths of HB leads GB/T 39542.3-2020介绍: 国家标准...
英文:Mechanical pencils for technical drawings—Part 3: Black leads—Bending strengths of HB leads GB/T 39542.3-2020介绍: 国家标准...