Machinery's Handbook, 31st Edition
2130
MEASURING SCREW THREADS Dimensions Over Wires of Given Diameter for Checking Screw Threads of American National Form (US Standard) and the V-Form
Dimension over Wires
Dimension over Wires
No. of Threads per Inch
No. of Threads per Inch
Wire Dia. Used
Dia. of Thread
Wire Dia. Used
Dia. of Thread
V- Thread
US Thread
V- Thread
US Thread
18 20 22 24 18 20 22 24 16 18 20 14 16 12 13 14 12 14 10 11 12 10 11 10 11 12
0.035 0.2588 0.2708 0.035 0.2684 0.2792 0.035 0.2763 0.2861 0.035 0.2828 0.2919 0.035 0.3213 0.3333 0.035 0.3309 0.3417 0.035 0.3388 0.3486 0.035 0.3453 0.3544 0.040 0.3867 0.4003 0.040 0.3988 0.4108 0.040 0.4084 0.4192 0.050 0.4638 0.4793 0.050 0.4792 0.4928 0.050 0.5057 0.5237 0.050 0.5168 0.5334 0.050 0.5263 0.5418 0.050 0.5682 0.5862 0.050 0.5888 0.6043 0.070 0.6618 0.6835 0.070 0.6775 0.6972 0.070 0.6907 0.7087 0.070 0.7243 0.7460 0.070 0.7400 0.7597 0.070 0.7868 0.8085 0.070 0.8025 0.8222 0.070 0.8157 0.8337 0.070 0.8300 0.8541 0.070 0.8493 0.8710
8 9
0.090 0.9285 0.9556 0.090 0.9525 0.9766 0.090 0.9718 0.9935 0.090 0.9910 1.0181 0.090 1.0150 1.0391 0.090 1.0535 1.0806 0.090 1.0775 1.1016 0.090 1.1476 1.1785 0.090 1.2726 1.3035 0.150 1.5363 1.5724 0.150 1.6613 1.6974 0.150 1.7601 1.7995 0.150 1.8536 1.8969 0.150 1.9786 2.0219 0.150 2.0651 2.1132 0.150 2.3151 2.3632 0.150 2.5170 2.5711 0.150 2.7670 2.28211 0.200 3.1051 3.1670 0.200 3.3551 3.4170 0.250 3.7171 3.7837 0.250 3.9226 3.9948 0.250 4.1726 4.2448 0.250 4.3975 4.4729 0.250 4.6202 4.6989 0.250 4.8402 4.9227 0.250 5.0572 5.1438
1 ∕ 4 1 ∕ 4 1 ∕ 4 1 ∕ 4
7 ∕ 8 7 ∕ 8 7 ∕ 8
10
8 9 8 9 7 7 6 6 5 5
15 ∕ 16 15 ∕ 16
5 ∕ 16 5 ∕ 16 5 ∕ 16 5 ∕ 16
1 1
1 1 ∕ 8 1 1 ∕ 4 1 3 ∕ 8 1 1 ∕ 2 1 5 ∕ 8 1 3 ∕ 4 1 7 ∕ 8 2 1 ∕ 4 2 1 ∕ 2 2 3 ∕ 4 3 1 ∕ 4 3 1 ∕ 2 3 3 ∕ 4 2 3 4 1 ∕ 4 4 1 ∕ 2 4 3 ∕ 4 4
3 ∕ 8 3 ∕ 8 3 ∕ 8
5 1 ∕ 2
7 ∕ 16 7 ∕ 16
1 ∕ 2 1 ∕ 2 1 ∕ 2
4 1 ∕ 2 4 1 ∕ 2
4 4
9 ∕ 16 9 ∕ 16
3 1 ∕ 2 3 1 ∕ 2 3 1 ∕ 4
5 ∕ 8 5 ∕ 8 5 ∕ 8
3 3
11 ∕ 16 11 ∕ 16
2 7 ∕ 8 2 3 ∕ 4 2 5 ∕ 8 2 1 ∕ 2
3 ∕ 4 3 ∕ 4 3 ∕ 4
9
5
13 ∕ 16 13 ∕ 16
10
… … … … …
Buckingham Simplified Formula which Includes Effect of Lead Angle.— The Formula (3) which follows gives very accurate results for the lower lead angles in determining mea - surement M . However, if extreme accuracy is essential, it may be advisable to use the involute helicoid formulas as explained later.
cos cos W A T B n # =
sin M E W A 1 n = + + ^ h
(3) where
(3a)
Theoretically correct equations for determining measurement M are complex and cumbersome to apply. Formula (3) combines simplicity with a degree of accuracy which meets all but the most exacting requirements, particularly for lead angles below 8 or 10 de - grees and the higher thread angles. However, the wire diameter used in Formula (3) must conform to that obtained by Formula (3a) to permit a direct solution or one not involving indeterminate equations and successive trials. Application of Buckingham Formula: In the application of Formula (3) to screw or worm threads, two general cases are to be considered.
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