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90 THE DISTRIBUTOR’S

90 THE DISTRIBUTOR’S LINK ROB LaPOINTE HARDNESS TESTING SMALL FASTENERS: USING MACROHARDNESS & MICROHARDNESS TECHNIQUES from page 10 Both ASTM A574 and SAE J429 require hardness testing to be done according to ASTM F606. ASTM F606 is familiar to many in the industry as a general fastener testing standard for mechanical properties such as hardness, tensile and proof-load testing. ASTM F606 is currently in revision 21 as ASTM F606/F606M- 21, including both imperial and metric fasteners. For hardness testing methodology, ASTM F606 refers to ASTM E18 for Rockwell hardness, ASTM E10 for Brinell hardness, ASTM E92 for Vickers macrohardness and Vickers and Knoop microhardness and ASTM E384 for microhardness in both Vickers and Knoop scales. This article will focus only on Rockwell macrohardness and Vickers and Knoop microhardness as they are the most common hardness methods and scales. Test Location ASTM F606 specifies the allowed location for measurements on a variety of fastener configurations. F606 allows hardness to be taken on the top of the head and wrenching flats of hex or square bolts (Figure 1). Measurement can also be taken on the unthreaded body of the fastener (Figure 2), on its end or in the arbitration location (Figures 3 and 10). The arbitration location is specified as the location hardness shall be taken on an externally threaded fastener when there is a dispute between two interested parties on the hardness results taken from an alternative location. The arbitration location is on a section of the FIGURE 3 THE ARBITRATION LOCATION FOR HARDNESS TESTING FASTENERS PER ASTM F606/F606M. fastener, approximately one diameter toward the head from the thread end (Figure 3). The hardness shall be taken at mid-radius and the result shall be an average of four readings taken approximately 90 degrees apart from one another as shown in Figure 3. This location provides the most accurate result of the core-hardness of a fastener, being sufficiently removed from surface and forming effects that could bias a core-hardness result taken from another location. The accuracy of a hardness measurement is not only dependent on the location of test, but also on the preparation of the sample, the condition, use and calibration of the hardness testing instrument and the spacing of the indentations. Rockwell, Brinell, Vickers and Knoop hardness methods all rely on accurately measuring the geometry of an indentation placed in the sample by the test instrument. Rockwell-B and Brinell both use a steel or tungsten carbide ball indenter, while Rockwell-A, Rockwell-C, Vickers, and Knoop all use a diamond indenter. The indentation’s depth or width is measured, depending on method, and that dimension is converted into a hardness value. The size of the indentation is directly related to hardness as softer materials will experience a greater deformation to an applied force than harder materials. The bigger the indentation, the softer the material. Sample Preparation Proper sample preparation is essential for accuracy. For macrohardness testing, the surface being tested must be clean, smooth and oriented 90 degrees from the direction the force is applied. ASTM F606 requires the removal of any surface oxides or coatings as well as any decarburized layers on the outside of the sample. While oxides and coating are easy to see, decarburization is not. Decarburization is carbon depletion in the surface of metal due to improper heat treatment. This result of carbon removal is a softer metal. The thread of the fastener is particularly affected by this defect and can cause a thread to strip rather than allowing the fastener to reach ultimate tensile strength. CONTINUED ON PAGE 130

THE DISTRIBUTOR’S LINK 91 EUROLINK FASTENER SUPPLY SERVICE 840 South Buncombe Road, Greer, SC 29650 TEL 864-801-0505 FAX 864-801-3606 EMAIL sales@eurolinkfss.com WEB www.eurolinkfss.com SOUTH CAROLINA PRODUCT LINE EXPANSION Eurolink Fastener Supply Service Expands its South Carolina Product Lines to Include ISO Torx Drive Socket and Machine Screws We are excited to announce that Eurolink Fastener Supply Service, a trusted leader in hard-to-find metric fastener solutions, is now stocking ISO Torx Drive Socket and Machine Screws. This addition broadens our extensive inventory, catering to the growing demand for premium-quality fastening solutions. The newly available ISO Torx Drive Screws include options in 8.8 alloy steel as well as both A2 and A4 stainless steel. Known for their reliability and precision, these screws are perfect for applications where high-strength, corrosion resistance, and a secure drive system are essential. Available Materials: 8.8 alloy steel, A2 stainless steel, and A4 stainless steel Drive Type: Torx, ensuring reduced cam-out and improved torque transmission Standards Compliance: ISO specifications include 14579, 14580, 14581, 14583, 14585, 7380-1, and 7380-2 Meeting Industry Needs With Versatility And Reliability At Eurolink, we prioritize delivering high-quality, specialized metric fasteners that meet the needs of industrial distributors throughout North America. Our ISO Torx Drive Socket and Machine Screws provide a robust solution for a wide range of industries, including automotive, aerospace, and general manufacturing. The addition of these products reaffirms our commitment to offering the most comprehensive range of European metric fasteners in the U.S. market. BUSINESS FOCUS ARTICLE EUROLINK FASTENER SUPPLY SERVICE