ASME B18.13-2017 pdf download
ASME B18.13-2017 pdf download.Screw and Washer Assemblies – SEMS(Inch Series).
2.4 Hex Cap Screws for SEMS
The hex head cap screws component of SEMS shall conform to the specifications for cap screws published in ASME B18.2.1, except for the following:
(a) The maximum diameter of the unthreaded shank shall be sufficient to allow free assembly and rotation of the washer relative to the screw.
(b) On hexagon cap screws threaded full length, the unthreaded length is the distance measured parallel to the axis of the screw from the underside of the washer to the face of a nonchamfered or noncounterbored standard GO ring gage. The unthreaded length is a maximum of two thread pitches (see Fig. 1). When required, threads extending closer than two pitches to the contacting face of the washer may be negotiated between the manufacturer and purchaser.
2.5 ApplicabiLity of Screw Sizes
To the extent that coverage is provided in the respective dimensional tables, numbered nominal sizes shall apply to all types of screws, including Type A tapping screws, and fractional nominal sizes shall apply to all types of screws except Type A tapping screws.
2.6 Washers for SEMS
The washer components of SEMS shall conform with the dimensions and specifications given for the various types in this Standard. It should be noted that the washers for SEMS may differ dimensionally from the equivalent over-the-thread washers as specified in ASME B18.21.1. Except for helical spring lock washers where the inside diameters are included for manufacturing purposes, the holes in the SEMS washers are not specified inasmuch as the washers shall be assembled onto the screw blanks before the threads are rolled. The edge contour of the hole on the head side of the washer and the size relationship between the washer inside diameter and the diameter of the unthreaded shank on the screw shall be such that the washer will be retained on the screw after the threads are rolled, and shall be free to rotate after assembly.
2.7 Finish
2.7.1 General. Unless otherwise specified by the purchaser, SEMS shall be supplied with a natural (asprocessed) finish, unpiated or uncoated. Where corrosion preventive treatment is required, SEMS shall be plated or coated as specified by the purchaser. The application of heavy coating deposits or supplemental treatments entailing organic compounds may result in a bonding of the SEMS components at points that abut.
3 DATA FOR HELICAL SPRING LOCK WASHER SEMS
3.1 Application
The helical spring lock washers covered herein are intended for general applications. Helical spring lock washers compensate for developed looseness between component parts of an assembly, distribute the load over a larger area for some head styles, and provide a hardened bearing surface.
32 Specifications
The washers shall conform to the specifications for helical spring washers published in ASME B18.21.1, except for modifications contained herein.
3.3 Washer Components
3.3.1 Dimensions. The dimensions of helical spring lock washers shall be as specified in Tables 1, 2, and 3. The corners at the outer and inner peripheries of the asher may be slightly rounded. However, the extent of the rounding shall be such that the bearing width of the washer section is not reduced to less than the equivalent of 7O% of the specified minimum section width. See Fig. 3 for the check method.
3.3.2 Tests. After heat treatment of the SEMS, the washers shall be removed, undamaged, from the screws for testing. The washers shall meet all test requirements for standard over-the-thread washers specified in
ASME B18.21.1.
3.4 Screw Components
(a) Socket head cap screws shall be assembled with washers shown in Table 1.
