ASTM F2437/F2437M-17(2023)

ABSTRACT This specification covers the requirements for carbon and alloy steel compressible-washer-type direct tension indicators (DTIs) capable of indicating a specified bolt tension in cap screws, bolts, anchors, and studs. These DTIs are intended for installation under a bolt or cap screw head, a hex nut, or against a hardened washer or other flat hardened surface. The following are two types of DTIs: Type 1 DTIs are suitable for comparatively large bearing surfaces and Type 2 DTIs are suitable for comparatively smaller bearing surfaces. DTIs shall have a configuration produced by extrusion, punching, pressing, or similar forming to permit a measurable decrease in thickness when placed in compression. The design shall be such that the degree of plastic deformation of the protrusions shall indicate the tension in a tightened cap screw, bolt, anchor, or stud. The process used for heat treatment of DTIs, if required, shall be through-hardening by heating to a temperature above the upper transformation temperature, quenching in oil, and then tempering by reheating to a suitable temperature to attain desired mechanical/performance properties. Protective coatings, platings, or finishes may be applied on the DTIs if specified. Compression load and hardness of the DTIs shall be determined by performing mechanical tests. SCOPE 1.1 This specification covers the requirements for carbon and alloy steel compressible-washer-type direct tension indicators (DTIs) capable of indicating a specified bolt tension in cap screws, bolts, anchors, and studs. 1.2 Direct tension indicators in inch sizes 1/4 through 21/2 in. and metric sizes M6 and M72 are covered. 1.3 Direct tension indicators have two styles and four grades for inch fasteners, Grades 5, 8, 55, and 105, and two property classes for metric fasteners, property classes 8.8 and 10.9 each of which differ in their compressive load requirements at a given gap (see Table 1 and Table 2). 1.3.1 Style 1 DTIs are suitable for comparatively smaller bearing surfaces. Style 1 DTIs are available in Grades 5 and 8, which differ in the amount of tension they indicate at a prescribed gap (see Table 1 and Table 3). 1.3.2 Style 2 DTIs are suitable for comparatively large bearing surfaces. Style 2 DTIs are available in Grades 55 and 105, which differ in the amount of tension they indicate at a prescribed gap (see Table 1 and Table 3). 1.4 Direct tension indicators are intended for installation under a bolt or cap screw head, a hex nut, or against a hardened washer or other flat hardened surface. 1.5 Recommended Fasteners—Fasteners meeting the requirements of the standards referenced in Table 3 are considered compatible with the DTI grade or class listed. 1.6 The values stated for Inch DTIs are expressed in inch-pound units and for Metric DTIs values are expressed in SI units. The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined. 1.7 The following precautionary statement pertains only to the test method portions, Section 12of this specification: This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.