ASME B18.2.3.1M:1999 pdf download METRIC HEX CAP SCREWS
1 INTRODUCTORY NOTES
1.1 Scope
1.1.1 This Standard covers the complete general anddimensional data for metric series hex cap scrcwsrecognized as American National Standard.
1.1.2 The inclusion of dimensional data in thisStandard is not intended to imply that al! of the sizesin conjunction with the various options described hereinarc stock items. Consumers should consult with suppliersconcerning lists of stock production hex cap screws.
1.2 Comparison With ISO Standards
1.2.1 Hex cap screws, sizes M5 to M64, as presentedin this Standard are harmonized to the extent possiblewith ISO 4014 or, for short screws threaded full lengthwith ISO 4017.Dimensional differences between thisStandard and 1SO 4014 or ISO 4017 are few.relativelyminor, and none will affect the functional interchangeability of screws manufactured to the requirements ofeither.
The following functional characteristics of screws.sizes M5 through M14 with nominal iengths 2 timesdiameter through 10 times diameter, sizes M16 throughM24 with nominal lengths 2 times diameter through150 mmm.and sizes M30 through M64 with nominallengths 2 times diameter and longer.are in agrcementbetween this Standard and ISO 4014 or ISO 4017.asapplicable:
(a) nominal diameters and thread pitches,
(b) body diameters.
(c) widths across flats and corners (sec para. 1.2.5),
(d) nominal head heights,
(e) nominal lengths and thread lengths, and
(f) thread dimensions.This Standard omits sizes Ml.6-M4M18.M22M27，M33.M39，M45M52、and M60，which areincluded in ISO 4014 and ISO 4017.This Standardincludes sizes M10 xI.S with15 mm width acrossflats.M72x6.M80x6,M90 x6.and M100x6 which are not in ISO 4014 or ISO 4017.
This Standard specifies some requirements that arenot included in ISO 4014 or ISO 4017.Dimensionalrequirements shown in bold type within the textand where noted within tables differ from, or arein addition to,ISO 4014 and/or ISO 4017, or, forsizes over M64. other relevant nonproduct ISO stan-dards. The technical differences between this Standardand the ISO standards are summarized in Appendix IV
1.2.2 At its mccting in Varna in May of 1977,1SO/TC2 studied several technical reports analyzing designconsiderations influencing determination of the bestseries of width across flats for hexagon bolts, screws.and nuts. A primary technical objective was to achievea logical ratio between the head or nut bearing surfacearea (which determines the magnitude of the compressive stress on the bolted members) and the tensilestress area of the screw thread (which governs theclamping force that can be developed by tighteningthe fastener).
Ml0 screws with 15 mm width across fats arecurrently being produced and used in the U.S. andmany other countries of the world. This size, however.is not an ISO standard, Uniess Ml0 screws with 15mm width across flats are specifically ordered, MI0screws with 16 mm width across flats shall be furnished
1.2.3 Letter symbols designating dimensional charac-teristics arc in accord with ISO 225ISO 4014.and[SO 4017, except where capitals have been used insteadof the lower case letters used in the ISO standards.
1.3 Terminology
For definitions of tcrms relating to fasteners or compo.nent features thercof used in this Standard, refer toASME B18.12

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