ASME B18.13:2017 pdf download Screw and Washer Assemblies – SEMS (Inch Series)
1 INTRODUCTION
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 notshown in this Standard may be considered SEMS; how-ever, these products must be covered by the purchaser’sdrawing or standard.
1.4Screw Heads
1.4.1 Head Styles.The head styles applicable tothe various types of SEMS shall be as depicted in theillustrations and designated in the tables for each type.Where only the slotted head SEMS are illustrated,itshould be understood that this Standard also applies tothe corresponding cross-recessed head.
1.5 Dimensions
All dimensions in this Standard are given in inchesunless stated otherwise.
1.6 Options
Options, where specified, shall be at the discretion ofthe manufacturer, unless otherwise agreed upon by themanufacturer and the purchaser.
1.7 Responsibility for Modification
Parts made to this Standard can be subject to theeffects of hydrogen embrittlement, either from elec-troplating operations or exposure in the environment.The manufacturer shall not be held responsible for modi-fications, such as plating (done by the purchaser tounplated SEMS supplied in the original order), whenthese modifications are not made by the manufacturer.1.8 Terminology
For definitions of terms relating to fasteners or compo-nent features thereof used in this Standard, refer toASME B18.12.
1.9 Reference Standards
The following is a list of publications referenced inthis Standard. The latest edition shall apply.
ASME B18.2.1，Square,Hex，Heavy Hex,and AskewHead Bolts and Hex,Heavy Hex, Hex Flange, LobedHead, and Lag Screws (Inch Series)
ASME B18.3, Socket Cap, Shoulder, Set Screws, and HexKeys (Inch Series)
ASME B18.6.3，Machine Screws,Tapping Screws,andMetallic Drive Screws (Inch Series)
ASME B18.13:2017 pdf download
