ASME B18.13 pdf download

ASME B18.13 pdf download Screw and Washer Assemblies – SEMS (Inch Series)
1.1 Scope
This Standard covers general and dimensional data pertinent to the various types of screw and captive washer assemblies, otherwise known as SEMS. SEMS products may include screws, tapping screws, or bolts in sizes No. 0 through 1 ⁄ 2 in. diameters in various grades and materials. The word SEMS is recognized in the United States as a generic term applicable to screw and washer assemblies. Also included in this Standard is Nonmandatory Appendix A illustrating the relative proportions of plain and conical washer SEMS. NOTE: The word lock, which appears in the names of products in this Standard, is a generic term historically associated with their identification and is not intended to imply an indefinite fixity in attachments where the fasteners are used.
1.2 Use and Application
The SEMS covered by this Standard are general pur- pose fasteners intended for mass production and other assembly operations where speed and convenience are paramount factors. Further attributes of the various washers, recognized herein, are given in detail for each type of SEMS. Products having washers of styles and shapes not shown in this Standard may be considered SEMS; however, these products must be covered by the purchaser’s drawing, standard, or the supplier’s standards.
1.3 Types of SEMS Included in this Standard are SEMS comprised of the following types of screws and washers:
(a) Helical Spring Lock Washers
(1) socket head cap screws (see Table 1)
(2) hex cap screws (see Table 2)
(3) machine screws (see Tables 2 and 3)
(4) tapping screws (see Tables 2 and 3)
(b) Tooth Lock Washers
(1) machine screws (see Tables 4 and 5)
(2) tapping screws (see Tables 4 and 5)
(3) hex cap screws (see Tables 4 and 5)
(c) Conical Spring Washers
(1) hex cap screws (see Table 6)
(2) machine screws (see Table 6)
(3) tapping screws (see Table 6)
(d) Plain Washers
(1) machine screws (see Table 7)
(2) tapping screws (see Table 7)
(3) hex cap screws (see Table 7)
(e) Products having washers of styles and shapes not shown in this Standard may be considered SEMS; how- ever, these products must be covered by the purchaser’s drawing or standard.
1.4 Screw Heads
1.4.1 Head Styles. The head styles applicable to the various types of SEMS shall be as depicted in the illustrations and designated in the tables for each type. Where only the slotted head SEMS are illustrated, it should be understood that this Standard also applies to the corresponding cross-recessed head.
1.5 Dimensions All dimensions in this Standard are given in inches unless stated otherwise.
1.6 Options Options, where specified, shall be at the discretion of the manufacturer, unless otherwise agreed upon by the manufacturer and the purchaser.
1.7 Responsibility for Modification Parts made to this Standard can be subject to the effects of hydrogen embrittlement, either from electroplating operations or exposure in the environment.

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