2022 ARP Catalog

30 24. What metallurgical issues cause common failures? The most common cause of failure of connecting rod bolts (and wheel bolts) is too little induced load (stretch) during installation. This allows the alternating load to impose cyclic loading on the bolt. Over tightening is also another cause, because the induced stress is too close to the yield point. 25. How do the various standards compare to each other with regard to fasteners? Where are the standards? A standard fastener is one that can be referenced from a nationally or internationally recog- nized standards document and may be produced by any interested manufacturer. In all fastener categories the custodian of each group (MS-AN-NAS) has tried to standardize the processing of specifications such as heat-treating per MIL-H-6875, cadmium plating per AMS QQ-P-416, passivation per AMS QQ-P-35 and testing, per MIL.-Std 1312, among others. ASTM stands for the American Society for Testing Materials, a large industry funded group used to write standards for many materials and testing procedures. It compares directly to AMS (Aerospace Material Standard). In the case of ARP, 100% raw material is purchased to AMS specification – with the excep- tion of special alloys used in proprietary products. All materials are carefully examined for proper chemistry – and finally, periodic examination by an independent laboratory. ARP con- sistently strives to exceed industry specifications for quality and product management. MS (Military Standards): MS bolt specifications cover a wide range of fastener hardware, high strength bolts, nuts and washers with spec’s for materials and processing. MS fasteners have various tensile strengths. AN (Army-Navy) Specifications: Generally lower strength bolts and studs primarily in the 125,000 psi UTS range. AN also covers a wide range of nuts, washers and other hardware. NAS (National Aerospace Standard): These specifications cover fasteners in the strength rang- es 160,000/180,000/200,000 psi UTS. ISO (International Standards Organization): ISO 9001-94: is a quality control system designed for manufacturers with design control. ISO 9002-94: is a quality control system designed for manufacturers who build parts to cus- tomer specifications, and do not have design control. ISO 9001:2015: is current ISO system well suited for manufacturers with engineering design functions, drawing control and statistical techniques to achieve demanding quality require- ments. AS (Aerospace Standard) AS9100:2016: is an Aerospace Quality Management System that includes and expands on all ISO requirements with focus to further improve product quality and meet or exceed cus- tomer requirements. Metallurgy for the Non-Engineer FASTENER TECH