Assembly - January 2009 - (Page 61) to shear force or vibration, this space allows the screw to move in the path of least resistance. The Sinuloc threads eliminate this space. By simultaneously pushing on both the pressure and the trailing flanks of the joint, the fastener creates prevailing tension within the joint itself. The fastener can be installed in standard tapped holes without damaging the mating threads, and it can be installed and reinstalled repeatedly. “Sinuloc is like being in a hallway with your shoulders stuck between the walls. You can’t move left or right,” says LeVey. Loss of clamp load due to thermal cycling is more problematic when driving into light metals, such as magnesium and aluminum, than when fastening steel. That’s because light metals have different rates of thermal expansion than the steel screws. To counter this, suppliers have designed screws specifically for aluminum and other light alloys. One example is the ALtracs thread-forming fastener from Semblex Corp. (Elmhurst, IL). The fastener’s threads have a 33-degree asymmetrical flank angle, which equalizes the strength ratio between the steel screw and the mating boss. This is achieved through balancing the cross-sectional area of the thread to reflect each material’s strength characteristics. The thread-forming zone consists of a tapered, noncircular point with thread-forming relief flats. The taper helps assemblers insert and align the fastener in the hole. It also decreases the amount of torque needed to start the thread-forming process. The flat areas in the zone provide relief during threadforming, reducing driving torque by approximately 30 percent. The screw’s circular cross section maximizes thread engagement compared with trilobular screw designs, providing high stripping torques, consistent vibration resistance and superior clamp-load generation. “The ALtracs fastener prevents loss of clamp load due to vibration and thermal cycling,” says Gene Simpson, director of engineering services for Semblex. The threads of the ALtracs fastener have a 33-degree asymmetrical flank angle, which equalizes the strength ratio between the steel screw and the mating boss. Photo courtesy Semblex Corp. and EJOT Verbindungstechnik We’re hearing that more and more, and it’s great news! 650 ton forming press custom engineered for a U.S. company that is expanding domestic capacity With hi-tech shop floors, U.S. manufacturers are again becoming globally competitive. The new automated workplace requires highly specialized equipment, and Multipress is meeting this demand with customized hydraulic presses featuring the latest in sensors, electronic controls, and advanced hydraulic technology. We can definitely help you to be more productive. Call us for an eye-opening quote on a custom engineered press. Columbus, Ohio • (614) 228-0185 sales@multipress.com www.multipress.com www.assemblymag.com January 2009 / ASSE M B LY 61 http://www.multipress.com http://www.multipress.com http://www.assemblymag.com
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