Machinery's Handbook, 31st Edition
1798 Metric Machine Screws Table 8. American National Standard Header Points for Metric Machine Screws Before Threading ANSI/ASME B18.6.7M-1999 (Withdrawn)
Screw Blank Before Rolling Thread
40°–45°
D P
L
D P
L
a
Nominal Screw Size and Thread Pitch
Point Diameter
Nominal Screw Length
Max. 1.33 1.73 2.12 2.46 2.80 3.60 4.25 5.82 7.36 8.90
Min. 1.21 1.57 1.93 2.24 2.55 3.28 3.85 5.30 6.71 8.11
Max.
13 13 16 20 25 30 40 40 40
M2 × 0.4 M2.5 × 0.45 M3 × 0.5 M3.5 × 0.6 M4 × 0.7 M5 × 0.8 M6 × 1 M8 × 1.25 M10 × 1.5 M12 × 1.75
45 a Header points apply to these nominal lengths or shorter. The pointing of longer lengths may require machining to the dimensions specified. All dimensions in millimeters. The edge of the point may be rounded and the end of point need not be flat nor perpendicular to the axis of screw shank. British Machine Screws Many of these classifications of fasteners are covered in British Standards BS 57:1951, “B.A. Screws, Bolts and Nuts”; BS 450:1958 (obsolescent), “Machine Screws and Ma - chine Screw Nuts (BSW and BSF Threads)”; BS 1981:1953, “Unified Machine Screws and Machine Screw Nuts”; BS 2827:1957 (obsolescent):1957, “Machine Screw Nuts, Pressed Type (B.A. and Whitworth Form Threads)”; BS 3155:1960, “American Ma - chine Screws and Nuts in Sizes Below 1 ∕ 4 inch Diameter”; and BS 4183:1967 (obsoles cent), “Machine Screws and Machine Screw Nuts, Metric Series.” At a conference orga nized by the British Standards Institution in 1965 at which the major sectors of British industry were represented, a policy statement was approved that urged British firms to regard the traditional screw thread systems—Whitworth, B.A. and BSF—as obsoles - cent, and to make the internationally-agreed ISO metric thread their first choice (with ISO Unified thread as second choice) for all future designs. It is recognized that some sections of British industry already using ISO inch (Unified) screw threads may find it necessary, for various reasons, to continue with their use for some time: Whitworth and B.A. threads should, however, be superseded by ISO metric threads in preference to an
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