Design News, February 2013

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Some types of captive panel screw hardware have been designed specifically for tool-only access, and are therefore especially well-suited to applications that must comply with security or safety requirements. Source: PennEngineering Reliability in a Clutch cessful outcome. First, the metal sheets into which the captive panel fastener will be installed must have adequate ductility to allow the displaced sheet material to cold flow into the undercut. Next, these metal sheets must be sufficiently softer than the fastener so that the fastener itself does not deform during the installation process. Finally, these sheets must meet the minimum thickness required by the particular fastener. As an example, one basic type of captive panel screw assembly requires a minimum sheet thickness of 0.036 inch (0.92 mm). Typically, there is no specified maximum thickness required for clinching into sheets. Sheet thickness may become a consideration, however, depending on the fastener's screw length. Some applications may be inappropriate for self-clinching hardware, especially when stainless-steel panels are involved, due to the relative fastener/ panel hardness issue. But compatible solutions do exist. An example is a captive panel fastener with a retainer made from 400 Series stainless, which installs reliably into a stainless sheet. The second mounting style of captive panel screws is the flare-mounted type. These panel fasteners with captive screws are usually one of the types recommended for stainless-steel appli- cations, and for most thin materials of any hardness. Unlike self-clinching versions, during installation a flaremounted fastener's shank deforms instead of the panel deforming, and requires minimal installation force. These fasteners likewise install flush on the backside of a panel. Also unlike selfclinching fasteners, they are appropriate for close centerline-to-edge applications. They are also appropriate for use in painted panels, since the paint thickness does not hinder attachment, unlike the self-clinching process, and no marring occurs during installation. One trade-off is the fact that an extra step is needed for panel preparation, since the mounting hole requires a countersink. The third mounting style, floating/ flaring-mounted fasteners, can install into stainless steel or any thin panel material, including PC boards, regardless of the panel's hardness. These are similar to flare-mounted types in that they deform during installation, require minimal squeezing force with punch and anvil to flare their retainer, and serve as practical hardware for close centerline-to-edge applications. An added advantage is the fact that they can compensate for mating thread misalignment, offering up to 0.81 inch (2.06 mm) of float within the mounting hole. Design News | february 2013 | w w w. d e s i gn n –47– ...a clutch, brake or power transmission part for that matter. Since 1903 Carlyle Johnson has solved some of history's toughest motion control challenges – it's what we love to do. Our precision electrical, mechanical, air and hydraulic power transmission products consistently prove reliable and dependable in every application. Underwater, on the ground and in the air, CJM is everywhere. Standard and Custom Clutch, Brake & Power Transmission Solutions 291 Boston Turnpike • Bolton, CT 06043 Phone: 860-643-1531

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