Bored hole size before tapping ( for thread forming )

■ for Metric Threads

SizeClassRecomm Hole Siz Max.ended e(mm) Min.thread engagement ratio (Estimation %)ref.Minor of interna (5H/ Max.diameter l threads 6H) Min.SizeClassRecom Hole Si Max.mended ze(mm) Min.thread engagement ratio (Estimation %)ref.Minor of intern (5H Max.diameter al threads /6H) Min. unit: mm
M1×0.25 ISO2X0.920.8980~1000.7850.729M8×1.25ISO2X7.527.3980~1006.9126.647
ISO3X0.910.8975~90ISO3X7.517.4180~95
M12025 ISO2X1.111.0980~10009850929M81ISO2X7.607.4980~10071536917
.×. ISO3X1.111.0975~90..×ISO3X7.607.5280~95..
M1403 ISO2X1.301.2680~10011421075M1015ISO2X9.389.2685~10086768376
.×. ISO3X1.301.2770~90..×.ISO3X9.419.2980~95..
M1.6×0.35 ISO2X1.471.4375~1001.3211.221M10×1.25ISO2X9.529.3880~1008.9128.647
ISO3X1.481.4470~95ISO3X9.509.4080~95
M204 ISO2X1.851.8075~100M12175ISO2X11.2711.1385~100
×. ISO3X1.871.8170~951.6791.567×.ISO3X11.2611.1785~9510.44110.106
M204 ISO2X2.342.2775~100M121ISO2X11.4211.2585~100
.5×.5 ISO3X2.342.2975~952.1382.013×.5ISO3X11.4011.2880~9510.67610.376
M3×0.5 ISO2X2.832.7675~1002.5992.459M12×1.25ISO2X11.5111.3780~10010.91210.647
ISO3X2.822.7675~95ISO3X11.5011.4080~95
M3.5×0.6 ISO2X3.303.2275~1003.0102.850M14×2ISO2X13.1713.0085~10012.21011.835
ISO3X3.283.2275~95ISO3X13.1513.0585~95
ISO2X3.733.6680~100ISO2X13.3613.2385~100
M4×0.7 ISO3X3.743.6775~953.4223.242M14×1.5ISO3X13.4013.2880~9512.67612.376
ISO2X4.684.6080~100ISO2X15.1715.0085~100
M5×0.8 ISO3X4.714.6275~954.3344.134M16×2ISO3X15.1515.0485~9514.21013.835
ISO2X5.605.5080~100ISO2X15.3515.2385~100
M6×1 ISO3X5.615.5380~955.1534.917M16×1.5ISO3X15.4015.2780~9514.67614.376