Machinery's Handbook, 31st Edition
988
Taps Table 8. Standard Metric Size Tap Dimensions for Screw Thread Insert (STI) Taps ANSI/ASME B94.9-2008 (R2018)
Tap Dimensions, inch
Overall length, L
Thread Length, I
Square Length, I 2
Shank Diameter, d 1
Size of square, a
Nominal Size (STI)
Thread Pitch, mm Coarse Fine
Blank Design No.
Blank Diameter
M2.2 M2.5
0.45 0.45 0.50 0.60 0.70 0.80
… … … … … … … …
1 1 1 1 1 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
1.88 1.94 2.00 2.13 2.38 2.50 2.72 2.94 2.94 3.38 3.16 3.59 4.03 3.81 4.25 4.03 4.69 4.47 4.91 4.69 5.13 4.91 5.44 5.13 5.75 5.44 6.06 5.75 6.38 6.06 6.69 7.00
0.56 0.63 0.69 0.75 0.88 1.00 1.13 1.25 1.25 1.66 1.44 1.66 1.81 1.81 2.00 1.81 2.22 2.00 2.22 2.22 2.50 2.22 2.56 2.50 2.56 2.56 3.00 2.56 3.00 3.00 3.19 3.19
0.19 0.19 0.19 0.25 0.25 0.31 0.38 0.44 0.44 0.44 0.41 0.50 0.63 0.56 0.69 0.63 0.75 0.69 0.75 0.75 0.81 0.75 0.88 0.88 1.00 0.88 1.06 1.00 1.13 1.06 1.13 1.25
0.141 0.141 0.141 0.168 0.194 0.255 0.318 0.381 0.381 0.367 0.323 0.429 0.542 0.480 0.590 0.542 0.697 0.652 0.760 0.697 0.800 0.760 0.896 0.896 1.021 0.896 1.108 1.021 1.233 1.108 1.305 1.430
0.110 0.110 0.110 0.131 0.152 0.191 0.238 0.286 0.286 0.275 0.242 0.322 0.406 0.360 0.442 0.406 0.523 0.489 0.570 0.523 0.600 0.570 0.672 0.672 0.766 0.672 0.831 0.766 0.925 0.831 0.979 1.072
No.4 No.5 No.6 No.8
M3
M3.5
M4 M5 M6 M7 M8
No.10
1 ⁄ 4
1 1
5 ⁄ 16
3 ⁄ 8 3 ⁄ 8 1 ⁄ 2
1.25
1
M10
1.5
1.25
… …
7 ⁄ 16 9 ⁄ 16
M12 M14
1.75 1.5 1.25
2
…
11 ⁄ 16
…
1.5
5 ⁄ 8 3 ⁄ 4
M16
2
…
…
1.5
11 ⁄ 16
M18
2.5
…
7 ⁄ 8
…
2.0 1.25
13 ⁄ 16 15 ⁄ 16
M20
2.5
2.0
…
1.25
7 ⁄ 8
1
M22
2.5
2.0 1.5
…
15 ⁄ 16
1 1 ⁄ 8
M24
3
…
1 1 ⁄ 16
… 2
1 1 ⁄ 4 1 1 ⁄ 8 1 3 ⁄ 8 1 1 ⁄ 4 1 1 ⁄ 2 1 3 ⁄ 8 1 5 ⁄ 8 1 3 ⁄ 4
M27
3
…
… 2
M30
3.5
…
… 2
M33
3.5
…
… 2
M36 M39
4 4
3 3
2 2
These taps are larger than nominal size to the extent that the internal thread they produce will accommodate a helical coil screw insert, which at final assembly will accept a screw thread of the nominal size and pitch. For optional necks, use Table 6 and dimensions for equivalent blank sizes. Ground Thread Taps: STI sizes M8 and smaller have external center on thread end (may be removed on bottom taps); STI sizes M5 through M10 will have an external partial cone center on shank end, with the length of the cone center approximately 1 ⁄ 4 of the diameter of shank; STI sizes larger than M10 inch may have internal centers on both the thread and shank ends. For runout tolerances of tap elements, refer to Table 14 using dimensions for equivalent blank sizes. For number of flutes, refer to Table 11 using dimensions for equivalent blank sizes. For general dimension tolerances, refer to Table 5b using Table 5a equivalent blank sizes.
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