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Distributor's Link Magazine Summer 2021 / Vol 44 No 3


102 THE DISTRIBUTOR’S LINK ROB LaPOINTE FASTENER SCIENCE: SHEAR TESTING – SINGLE AND DOUBLE SHEAR FOR FASTENERS from page 10 FIGURE 2 FRICTIONAL FORCE IS THE PRODUCT OF THE NORMAL FORCE AND THE COEFFICIENT OF FRICTION µ. FIGURE 4 BEARING CONNECTION When a joint is tightened in this manner, there are no shear loads on the fastener itself, even if there are shear loads on the assembly. The shear loads are carried by the frictional force that is created by the tensioned fastener. This type of joint is known as a Slip-critical joint and relies on the friction in the joint rather than the shear properties of the fastener to keep the joint from slipping. The Slipcritical joint is illustrated in figure 3. Notice that the bolt itself does not bear the load needed for the joint to not slip, but rather it is carried by the fiction created through tensioning of the bolt-nut assembly. Fasteners used in the Bearing Connection application must be able to withstand shear loads applicable to the conditions that will be experienced in service. Thus, it is paramount to the performance qualification of these fasteners that shear testing be performed and that the fastener is able to withstand the loads necessary to achieve good performance. Testing fasteners for shear properties is typically done in one of two ways, single shear or double shear. Single shear tests the fastener in one plane and double shear tests the fastener in two planes. Figure 5 illustrates the two types of shear testing. The test chosen depends on the application, specification and configuration of the fastener although, often times, the two tests are interchangeable and either test can provide the necessary data. The principal difference between the two tests is the testing fixture. Single shear creates a shearing force in one plane and double shear creates a shearing force in two parallel planes. FIGURE 3 SLIP-CRITICAL JOINT The second principal way fasteners are used in a Bearing Connection where the bolt itself bears the shear load of the joint rather than the friction. Figure 4 illustrates a bearing connection where there is little or no clamp-load created by tensioning the fastener. This type of joint relies on the shear strength of the fastener to hold the joint in registration rather than relying on the tensile strength of the fastener to create friction in the joint assembly. FIGURE 5 SINGLE SHEAR TEST ASSEMBLY (LEFT) AND DOUBLE SHEAR TEST ASSEMBLY (RIGHT) CONTINUED ON PAGE 158

SETKO FASTENERS THE DISTRIBUTOR’S LINK 103 300 N Klick Street, Unit A, Hampshire, IL 60140 TEL 630-800-6377 EMAIL WEB BUILDING RELATIONSHIPS THAT CUSTOMERS CAN COUNT ON The name “Setko” will sound familiar if you have been in the fastener industry for some time. Setko, a family owned business, continues to stand firm in its belief of strong customer service and long-lasting relationships. At Setko, we offer our customers more than great pricing. Setko builds relationships that customers can count on, quality they can trust and a personal commitment to each company no matter how small or large. Today, Setko Fasteners continues its legacy by opening their doors to all companies looking to expand and develop strong customer / supplier relationships. Whether it’s domestically manufactured or imported socket product, hard to find semi-standards, or items that re-quire secondary operations such as plating, patching or drilling - Setko Fasteners will provide the finished product and save you valuable time and money! Setko already stocks Hex Socket Set Screws with BUSINESS FOCUS ARTICLE every point style in Alloy and Stainless, Metric and Standard sizes. In addition, Setko has a full line of Socket Head, Button and Flat Head Cap Screws - Plain and Zinc Plated. Setko Fasteners is adding new product every day! We are expanding our lines to include more Socket Shoulder Bolts, Square Head Set Screws, Nylon and Brass Tip Set Screws, Short and Long Arm Hex Keys, 6-Lobe (Torx) Keys, Hex Jam Screws, and Dowel Pins! Setko continues to offer Mill Shipments and blanket orders with releases over a full year to support each customer’s monthly requirements. Setko works directly with each customer to fulfill their requirements by analyzing yearly usage and processing parts accordingly. This reduces costs and ensures product is available when needed. Please contact Setko Fasteners - your full service supplier.

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