FASTENINGS & ADHESIVES FEATURE
MEETING THE REQUIREMENTS Regardless of self-clinching fastener type or style, designers should understand that the host metal sheet material must always meet three basic requirements for success: • Metal sheets into which the fastener will be installed must have adequate ductility to allow the displaced sheet material to cold flow into the undercut without fracturing. • These metal sheets must be sufficiently softer than the fastener so that the fastener does not significantly deform during the installation process.
• Sheets must meet the minimum thickness required by the particular fastener. Typically, there is no specified maximum thickness required for the sheets. Many mechanical fastener attachment
applications in the appliance industry demand corrosion resistance and hardness, while contributing to thinner and lighter designs. Considering self- clinching technology, specific fasteners manufactured exclusively for use in stainless steel have been developed. However, a prevalent misconception is that any stainless self-clinching fastener will perform without fail when installed
in any stainless sheet. This is not true. In fact, standard stainless self-clinching fasteners made from 300 Series cannot be expected to perform reliably in 300 Series stainless sheets, due to the relative hardness issue. Appropriate stainless self-clinching fasteners for installation into 300 Series stainless sheets include types manufactured from 400 Series stainless. Those made from special alloy (precipitation hardened) stainless will offer even higher corrosion resistance. Depending on type, these fasteners can be used effectively in sheets with hardness ranges from HRB 88 to HRB 92.
THE RIGHT SOLUTION Most fasteners designed to provide permanent load-bearing threads in thin materials require both sides of a work piece to be accessible during installation and final component attachment. If there is access from only one side, so-called ‘blind’ applications, ‘blind’ threaded inserts can be used. These fasteners are suited (where other permanently installed threaded hardware is not) for tubing, extrusion and other similar applications. Such inserts are made from aluminium, brass, steel or stainless steel and are
designed to be used instead of tapped holes, weld nuts, rivets, and self-drilling or tapping screws. Installed from the accessible ‘front’ side of a work piece, they will provide strong permanent metal threads in metal or plastic sheets as thin as .020” / 0.50mm. As with self-clinching fasteners, blind threaded inserts eliminate any need for additional hardware beyond a mating part. A variety of blind threaded insert types are available, including large diameter and low-profile head designs for enhanced strength, types for use in any material thickness, and heavy-duty styles enabling sheet-on-sheet attachment. Threaded self-clinching fastener
and blind insert technologies can satisfy a wide range of attachment applications for appliances, but distinct parameters and requirements presented by an application will always prevail during decision-making. Partnering at the start of the design process with an experienced hardware manufacturer can help with specifying the right solution.
Penn Engineering
www.pemnet.com Enter 204
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Enter 8 / DESIGNSOLUTIONS Enter 9 DESIGN SOLUTIONS | MAY 2015 13
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