Machinery's Handbook, 31st Edition
1726 Metric Screws and Bolts Table 15. Socket Head Cap Screws (Metric Series)—Length of Complete Thread ANSI/ASME B18.3.1M-1986 (Withdrawn)
Length of Complete Thread, L T
Length of Complete Thread, L T
Length of Complete Thread, L T
Nominal Size
Nominal Size
Nominal Size
M1.6
15.2 16.0 17.0 18.0 20.0 22.0
M6 M8
24.0 28.0 32.0 36.0 40.0 44.0
M20 M24 M30 M36 M42 M48
52.0 60.0 72.0 84.0 96.0
M2
M2.5
M10 M12 M14 M16
M3 M4 M5
108.0 Grip length, L G equals screw length, L , minus L T . Total length of thread L TT equals L T plus 5 times the pitch of the coarse thread for the respective screw size. Body length L B equals L minus L TT . The minimum thread length for hex lag screws is equal to one-half the nominal screw length plus 12 mm, or 150 mm, whichever is shorter. Screws too short for this formula to apply are threaded as close to the head as practicable. Metric Screw and Bolt Diameter-Length Combinations.— For a given diameter, the rec - ommended range of lengths of metric cap screws, formed hex screws, heavy hex screws, hex flange screws, and heavy hex flange screws can be found in Table 17 , for heavy hex structural bolts in Table 18, for hex lag screws in Table 16, for round head square neck bolts in Table 19, and for socket head cap screws in Table 20. No recommendations for diameter- length combinations are given in the Standards for hex bolts and heavy hex bolts. Hex bolts in sizes M5 through M24 and heavy hex bolts in sizes M12 through M24 are standard only in lengths longer than 150 mm or 10 D , whichever is shorter. When shorter lengths of these sizes are ordered, hex cap screws are normally supplied in place of hex bolts and heavy hex screws in place of heavy hex bolts. Hex bolts in sizes M30 and larger and heavy hex bolts in sizes M30 and M36 are standard in all lengths; however, at manu facturer’s option, hex cap screws may be substituted for hex bolts and heavy hex screws for heavy hex bolts for any diameter-length combination.
Table 16. Recommended Diameter-Length Combinations for Metric Hex Lag Screws ANSI/ASME B18.2.3.8M-1981 (Withdrawn)
Nominal Screw Diameter
Nominal Screw Diameter
Nominal Length, L
Nominal Length, L
5
6
8 1012162024
10 12 16 20 24
8
… … … … … … … 90
d
d d d d d
10 12 14 16 20 25 30 35 40 45 50 60 70 80
… … … … … … 100
d d
d d d d d
… … … … … 110 … … … … … 120
… …
d d d
d d d d
d d d
d d d d
… … … … 130
… … … … … … … …
d d d d
d d d
… … … 140
d d d d d
d d d
… … 150
d d d d d d
d d d
… 160
d d d d d d d
d d d
180 200 220 240 260 280 300
… … … … … …
d d d d d d d d
d d
d d d d d d d d
d d
… … … … … … … … … … … … … … … … … … … …
d d d d d d d d
d
d d d d d d d d
d
…
d d d d d d d
d
… … … …
d d d d d d
d
d d d d d d
d
All dimensions are in millimeters. Recommended diameter-length combinations are indicated by the symbol d .
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