螺纹底孔直径
公制普通粗牙螺纹
螺纹代号M2×04M3×05M4×07M5×08M6×10M8×125M10×15M12×175M14×20M16×20M18×25M20×25M24×30M30×35M36×40M42×45M45×45M48×50钻头直径HSS16253342506885103120140155175210265320375405430硬质合金1652553443516987105122142157177………………………………
公制细牙螺纹
螺纹代号M2×025M3×035M4×05M5×05M6×075M8×10M8×075M10×10M10×125M10×075M12×15M12×125M12×10M14×15M14×10M16×15M16×10M18×15M18×10M20×20M20×15M20×10M24×20M24×15M24×10M30×3钻头直径HSS17527354563773988931051081112513014515016517181851922022523027硬质合金17527355455635717359189935107109111127131147151167171183187191……………………
fM30×2M30×15M30×15M36×30M36×2M36×15M42×4M42×3M42×2M42×15M45×4M45×3M45×2M45×15M48×4M48×3M48×2M48×15
2828529330340345383940405414243435440450460465
………………………………………………………………………………………………
攻螺纹前底孔直径的确定
（1）普通螺纹攻螺纹前底孔的钻头直径
f（2）非螺纹密封的管螺纹攻螺纹前钻底孔的钻头直径
螺纹公称直径（