ASME B18.2.3.2-2005 pdf free download.Metric Formed Hex Screws.
(n) This Standard covers the complete dimensional and general data for metric formed hex screws recognized as American National Standard. Formed hex screws are cold formed products with fully upset (non-trimmed) heads. Formed hex screws are standard only in sizes M5 thru M24, with lengths up to 150 mm, or 10 times nominal screw size, whichever is shorter.
(b) The inclusion of dimensional data in this Standard is not intended to imply that all of the sizes in conjunction with the various options described herein are stock items. Consumers should consult with suppliers concerning lists of stock production formed hex screws.
2 COMPARISON WITH ISO STANDARDS
Because of numerous differences between this Standard and ISO 4015, a detailed summary is included in Appendix C.
At its meeting in Vama, May 1977, ISO/TC2 studied several technical reports analyzing design considerations influencing determination of the best series of width aCToss flats for hexagon bolts, screws, and nuts. A primary technical objective was to achieve a logical ratio between underhead (nut) bearing surface area (which determines the magnitude of the compressive stress on the bolted members) and the tensile stress area of the screw thread (which governs the clamping force that can be developed by tightening the fastener). Table 1 lists the sizes selected by I50/TC2 to be ISO standard.
M10 screws with 15 mm width across flats are Currently being produced and used in the US. and many other countries. This size, however, is not an ISO standard. Unless M10 screws with 15 mm width aCross flats are sefially ordered, M10 screws with 16 mm width across flats shall be furnished.
(c) Letter symbols designating dimensional charac- teristics are in accord with those used in ISO standards, except that capital ltters have been used instead of the lower case ltters used in IS0 standards.
3 TERMINOLOGY
For definitions of terms relating to fasteners or component features thereof used in this Standard, refer to American National Standard ASME B18.12.
The transition from full thread to incomplete thread shall be smooth and uniform. The major diameter of the incomplete threads shall not exceed the actual major diaim’ter of the complete (full form) threads. The transition threads shall have a rounded root contour.
6.6.5 Position of Body-to-Thread. For products with cut threads, at maximum material condition, the axis of the screw body, 0, (derived median line), over a length equal to the nominal screw diameter from the last scratch of thread, shall be within the positional tolerance zone diameter specified in Table 2 with respect to the axis of the thread, over a length equal to the nominal screw diameter from the last complete thread. A gage and gaging procedure for checking body position is given in Nonmandatory Appendix B.
6.7 Screw Threads
6.7.1 Thread Series and Tolerance aass. Screw threads shall be general purpose metric screw threads with tolerance Class 6g conforming to ASME Bi .13M, unless otherwise specified by the purchaser, For screws with additive finish, size limits for tolerance Class 6g apply prior to coating, and the thread after coating is subject to acceptance using a basic (tolerance position is) size GO thread gage and tolerance Class 6g thread gage for either minimum material LO or NOT GO.
6.7.2 Thread Gaging. Unless otherwise specified, dimensional acceptability of screw threads shall be based on System 21 of ASME B1.3M.
6.8 MaterIals and Mechanical Properties
6.8.1 Steel. Unless otherwise specified, steel screws shall conform to the requirements of ASTM F 568M.
6.8.2 Corrosion-Resistant Steels. Unless other. wise specified, screws made of corrosion-resistant steels shall conform to the requirements of ASTM F 738M.
6.8.3 Nonferrous Metals. Unless otherwise sped- tied, nonferrous screws shall conform to the require- merits of ASTM F 468M.
6.9 FInish
Unless otherwise specified, screws shall be supplied with a natural (as processed) finish, unplated or uncoated, in a clean condition and lightly oiled.
6.10 Identification Symbols
Identification marking symbols shall be on top of the screw heads and shall be raised or indented at the manufacturer’s option, unless otherwise specified at the time of ordering.