FALL 2024

10 THE DISTRIBUTOR’S

10 THE DISTRIBUTOR’S LINK Rob LaPointe EXPEDITE TESTING SERVICE Rob LaPointe is a noted authority in materials and fastener technology. With extensive experience in the management and science of materials testing laboratories combined with master’s degrees in physics and education, he excels at bringing solutions to the client. Working specifically in the fastener testing industry, he has developed expertise in mechanical, nondestructive, metallurgical and chemical testing. With a background of 20 years in physics education, Rob is effective at communicating complex ideas in a simple and understandable manner, communicating well with clients enabling them to make informed decisions about their products and business. Rob is President/CEO of Expedite Testing Service, 11645 Riverside Drive, Suite 127, Lakeside, CA 92040. Tel: 619-736-7872, Cell: 909-254-1278 or visit www.expeditetest.com. HARDNESS TESTING SMALL FASTENERS: USING MACROHARDNESS & MICROHARDNESS TECHNIQUES Testing the performance of the fasteners we manufacture or resell is an essential part of most production standards. While tensile, microstructure and discontinuity testing all may be required on the products we sell, the single most informative property of a metal is its hardness. The hardness of a material is a measure of its resistance to being deformed when applying force to it. Knowing the hardness of a metal informs us of its strength and processing history. Hardness is directly correlated to the quench and temper process of heat treating low-alloy carbon steel and the precipitation and solution hardening of many types of stainless-steel. Hardness data can be used to determine the degree and depth of case hardening and it is useful in determining the presence of many of the detrimental effects to metal caused by poor production and heat treatment such as decarburization, alloy segregation and the evaluation of FIGURE 2 ROCKWELL HARDNESS INDENTATIONS ON THE UNTHREADED PORTION OF A SOCKET-HEAD CAP SCREW TECHNICAL ARTICLE FIGURE 1 ROCKWELL HARDNESS INDENTATIONS ON THE WRENCHING FLATS OF A HEX-HEAD CAP SCREW inclusions (pollutants) in the melt of cast material. While detailed data sets measuring hardness in specific locations can tell us much about the condition of metal, a general core-hardness test is what most standards require. Core-hardness is a hardness measure of the bulk of a through-hardened piece of metal or the unaltered portion, below the surface, of a product that has a hardness treatment near its surface. Throughhardening is the effect of the heat treatment process that achieves the same hardness throughout the material. Assuming the metal is the same hardness from the surface to the interior and that no surface effects are altering the hardness at the surface, a core-hardness measurement can be taken on the surface of a sample or on a properly prepared section revealing the interior of the sample. Fasteners made to ASTM A574, SAE J429 and ISO 898-1 standards are all examples of throughhardened products that can have their core-hardness measured at the surface or on an interior section. CONTINUED ON PAGE 90