Machinery's Handbook, 31st Edition
Metric Machine Screws 1791 Table 1. American National Standard Thread Lengths for Metric Machine Screws ANSI/ASME B18.6.7M-1999 (Withdrawn) L U L U L US
Pan, Hex, and Hex Flange Head Screws
Flat and Oval Countersunk Head Screws
Heat-Treated Recessed Flat Countersunk Head Screws
L U
L
L US
L U L L
B
L L US
Nominal Screw Length a
Full Form Thread Length c
Nomi nal Screw Length Equal to or Shorter than a
Unthreaded Length b
Unthreaded Length b
Nominal Screw Size and Thread Pitch
Nomi nal Screw Length Longer than a
To and Includ
Max d
Max e Over
ing Max d
Max e
Min 25.0 25.0 25.0 38.0 38.0 38.0 38.0 38.0 38.0
6 8 9
1.0 1.1 1.2 1.5 1.8 2.0 2.5 3.1 3.8 4.4
0.4 0.5 0.5
6 8 9
30 30 30
1.0 1.1 1.2 1.5 1.8 2.0 2.5 3.1 3.8 4.4
0.8 0.9 1.0 1.2 1.4 1.6 2.0 2.5 3.0 3.5
30 30 30 50 50 50 50 50 50 50
M2 × 0.4
M2.5 × 0.45
M3 × 0.5
10 12 15 18 24 30 36
0.6 10 50 0.7 12 50 0.8 15 50 1.0 18 50 1.2 24 50 1.5 30 50 1.8 36 50
M3.5 × 0.6
M4 × 0.7 M5 × 0.8
M6 × 1
M8 × 1.25 M10 × 1.5
M12 × 1.75 38.0 a The length tolerances for metric machine screws are: up to 3 mm, incl., ± 0.2 mm; over 3 to 10 mm, incl., ± 0.3 mm; over 10 to 16 mm, incl., ± 0.4 mm; over 16 to 50 mm, incl., ± 0.5 mm; over 50 mm, ± 1.0 mm. b Unthreaded lengths L U and L US represent the distance, measured parallel to the axis of screw, from the underside of the head to the face of a nonchamfered or noncounterbored standard GO thread ring gage assembled by hand as far as the thread will permit. c Refer to the illustrations for respective screw head styles. d The L US values apply only to heat-treated recessed flat countersunk head screws. e The L U values apply to all screws except heat-treated recessed flat countersunk head screws. All dimensions in millimeters.
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