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Distributor's Link Magazine Spring 2018 / Vol 41 No2


38 THE DISTRIBUTOR’S LINK PENN ENGINEERING 5190 Old Easton Road, Danboro, PA 18916 TEL 1-800-237-4736 FAX 215-766-0143 EMAIL WEB THE ‘HARD FASTENER FACTS’ FOR CLINCHING INTO STAINLESS by Michael J. Rossi, Marketing Services Supervisor Designers will turn to self-clinching fasteners when they need a practical method to provide threads in thinmetal sheets. The fasteners install permanently; reduce hardware; and promote thinner and lighter designs. In stainless applications, though, designers may run into some particularly hard choices. A prevalent misconception is that all stainless self-clinching fasteners will perform as intended in all stainless sheets. But the relative hardness of fastener and sheet looms as an overriding influence, because self-clinching requires that the fastener always be harder than its host sheet. In general, installation of self-clinching fasteners is accomplished by pressing the fastener into place in a properly sized drilled or punched hole. This process causes displaced sheet material (“softer” than the fastener) to cold flow into a specially designed annular recess in the shank or pilot of the fastener, permanently locking the fastener in place. For effective installation into stainless, however, users should realize that work hardening can occur around the mounting hole during the process. Every effort must be made to enable the displaced sheet material to flow as intended. Our ongoing recommendation is that proper installation can best be accomplished by using a special anvil with a raised ring, which acts as a second displacer of the stainless sheet material (thereby ensuring that the annual groove of the fastener is filled). With differing stainless hardness levels available and widely varying degrees of desired corrosion resistance, decision-making can become complicated. Following are ASSORTMENT OF VARIOUS TYPES OF STAINLESS STEEL SELF-CLINCHING FASTENERS some guidelines and hardware profiles to help make the job easier when selecting stainless fasteners for 300 Series stainless applications (the most-often used stainless panel material): Fastener Material Standard stainless self-clinching fasteners made from 300 Series cannot be expected to perform reliably in 300 Series stainless sheets, due to the hardness relativity issue. These fasteners can, however, serve ideally when installed in other types of metal sheets (steel or aluminum) whose hardness is 70 or less on the Rockwell “B” scale (also designated HRB 70). The proper fastener solutions for installation into 300 Series stainless sheets include types manufactured from 400 Series stainless or those made from special alloy (precipitation hardened) stainless. Depending on type, these fasteners can be used effectively in sheets with hardness ranges from HRB 88 to HRB 92. TECHNICAL ARTICLE CONTINUED ON PAGE 126



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