Machinery's Handbook, 31st Edition
British Standard ISO Metric Screw Threads 2047 Table 4. Lengths of Thread Engagements for Short, Normal, and Long Categories Basic Major Diameter d Short Normal Long Basic Major Diameter d Short Normal Long
Length of Thread Engagement
Length of Thread Engagement
Up to and Incl.
Up to and Incl.
Up to and Incl.
Up to and Incl.
Up to and Incl.
Up to and Incl.
Pitch P
Pitch P
Over
Over
Over
Over
Over
Over
0.2
0.5
0.5 0.6 0.7 0.5 0.6 0.8
1.4 1.7 1.5 1.9 2.6 2
1.4 1.7 1.5 1.9 2.6 2
1
4
4
12
12 19 25 36 45 53 63 22 28 45 56 71 85 95 36 53 71 60 80
0.99 1.4
0.25 0.6
1.5
6.3 8.5
6.3 19 8.5 25
0.3 0.2
0.7 0.5
2 3
22.4 45
12
12 15 18 21 15 19 24 28 32 12 18 24 36 20 26 40
36 45 53 63 45 56 71 85 95 36 53 71 60 80
0.25 0.6 0.35 0.8 0.45 1.3 0.35 1 0.4 1
3.5 15
1.4
2.8
4
18
1
3
3
4.5 21
1.3
3.8
3.8
1.5
7.5 9.5
7.5 22 9.5 28
1
3
3
2 3 4 5 6 2 3 4 6 3 4 6
0.5 0.6 0.7
1.5 1.7
1.5 1.7 2.2 2.5 2.4 2
4.5
4.5
15 19 24 32 12 18 24 36 20 26 40
5 6
5 6
45
90
2.8
5.6
2
0.75 2.2
6.7 7.5 7.1
6.7 7.5 7.1
5.5 28
0.8
2.5
0.75 2.4
1
3
3 4 5
9
9
5.6 11.2
90 180
1.25 4
12 15
12 15 11 13 16 18 24 30
1.5
5
106 106
1
3.8
3.8 11 4.5 13 5.6 16
1.25 4.5
180 300
1.5
5.6
118 118
11.2 22.4
1.75 6
6 8
18 24 30
2
8
2.5 10
10
All dimensions are given in millimeters
T
EI
ES
T = Tolerance es and ES = Upper Deviations ei and EI = Lower Deviations Zero Line
ei
es
T
Fig. 2. Tolerance Positions with Respect to Zero Line (Basic Size) Design Profiles.— The design profiles for ISO metric internal and external screw threads are shown in Fig. 3 . These represent the profiles of the threads at their maximum metal condition. It may be noted that the root of each thread is deepened so as to clear the basic flat crest of the other thread. The contact between the thread is thus confined to their slop - ing flanks. However, for nut threads as well as bolt threads, the actual root contours shall not at any point violate the basic profile. Designation.— Screw threads complying with the requirements of the Standard shall be designated by the letter M followed by values of the nominal diameter and of the pitch, expressed in millimeters, and separated by the sign × . Example: M6 × 0.75. The absence of the indication of pitch means that a coarse pitch is specified. The complete designation of a screw thread consists of a designation for the thread sys tem and size, and a designation for the crest diameter tolerance. Each class designation consists of: a figure indicating the tolerance grade; and a letter indicating the tolerance
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