Machinery's Handbook, 31st Edition
992
Taps Table 12. Pulley Taps, Fractional Size (High-Speed Steel, Ground Thread) ANSI/ASME B94.9-2008 (R2018)
L
I 4
I
I
I 2
a
1
d 1
+0.03 -0.03 d 1
Threads per Inch NC UNC
Length d of Shank Close Tolerance, I 4
Dia. of Shank, d 1
Size b of Square, a
Dia. of Tap
Number of Flutes
Length Overall, L
Thread Length, I
Neck Length, I 1
Square Length I 2
20 18 16 14 13 11 10
4 4 4 4 4 4 4
6, 8 6, 8
1.00 0.38 0.31 1.13 0.38 0.38 1.25 0.38 0.44
1.50 1.56 1.63 1.69 1.69 2.00 2.25
0.255 0.191 0.318 0.238 0.381 0.286 0.444 0.333 0.507 0.380 0.633 0.475 0.759 0.569
1 ⁄
4
5 ⁄
16
6, 8, 10
3 ⁄
8
6, 8
1.44
0.44 0.50 0.50 0.56 0.63 0.69
7 ⁄
16
6, 8, 10, 12 1.66 6, 8,10,12 1.81
1 ⁄ 5 ⁄ 3 ⁄
2 8 4
10,12
2.00 0.75 0.75
Tolerances for General Dimensions
Diameter Range Tolerance
Diameter Range Tolerance
Element
Element
Overall length, L Thread length, I Square length, I 2 Neck length, I 1
±0.06 ±0.06 ±0.03
4 to 4 to 4 to 4 to
Shank Diameter, d 1 a Size of Square, a b Length of close tolerance shank, I 4
1 ⁄ 1 ⁄ 1 ⁄ 1 ⁄
3 ⁄ 3 ⁄ 3 ⁄ 3 ⁄
4 to 4 to 8 to 4 to
1 ⁄ 1 ⁄ 3 ⁄
1 ⁄ 1 ⁄ 5 ⁄
- 0.005 - 0.004 - 0.006
4 4 4
2
2 4
c
d
1 ⁄
3 ⁄
4
4
a Shank diameter, d b Size of square, a , is equal to 0.75 d
1 , is approximately the same as the maximum major diameter for that size.
1 to the nearest 0.001 in.
c Neck length, I
1 , is optional with manufacturer.
d Length of close tolerance shank, I 4 , is a min. length that is held to runout tolerances per Table 14. These taps are standard with plug chamfer in H3 limit only. All dimensions are given in inches. These taps have an internal center in thread end. For standard thread limits, see Table 20. For runout tolerances of tap elements, see Table 14.
L
L
I 1
I
I
I
2
I 2
d 1
d 1
L
I
I 2
d 1
Straight and Taper Pipe Tap Dimensions, Ground and Cut Thread (Table 13a and Table 13b)
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