FALL 2014

42 THE DISTRIBUTOR’S

42 THE DISTRIBUTOR’S LINK Industrial Rivet & Fastener Co. 200 Paris Avenue Northvale, NJ 07647 Tel: 1-800-289-7483 (1-800-BUY-RIVET) Fax: 201-750-1050 Email: info@rivet.com www.rivet.com THE ART & SCIENCE OF MANDREL PRODUCTION by Steven Sherman, VP Engineering Blind rivets have been produced since the mid 1900’s, and although many blind riveting technologies have evolved since – one constant has remained: the mandrel. Used in common blind rivet assemblies, the mandrel is a key component, and often the most critical, in the proper functioning of a blind rivet. It provides the rivet body retention and gives it the renowned “pop” or “click” sound when it breaks. To date, the mandrel in a blind rivet assembly is still the best method to provide secondary expansion in a blind rivet application. The Purpose By design, the mandrel is intended to resist corrosion and retain the rivet body as an assembly in transport until its eventual use. It is put into use when the mandrel is pulled through the rivet body by a mechanical tool to a pre-determined force, expanding the rivet body and then breaking at a specific point when the force is achieved. The spent mandrel is ejected into the riveting tool while the remaining slug is retained in the rivet body. Clearly this task is not as simple as it may seem to accomplish. And while mandrels are typically made on conventional construction nail headers, they are not considered easy products to manufacture – even by machine manufacturers’ own claims. The Design The mandrel has a few key features that are important to its proper functioning, including the: • Wire Tensile Strength • Wire Coating • Wire Size • Head Design, Diameter and Shape • The Retention Point • The Breakload and Break Point Location • The Cutoff The wire strength is a configured alloy with a specific tensile range. Without this tensile range being held to tight limits, the mandrel’s breakpoint, breakload, head and cutoff would all be affected. More importantly, there is a direct correlation between the wire tensile strength and the breakload. The Industrial Fasteners Institute (IFI) dictates what the breakloads should be and without properly specified wire, it might not be possible to achieve the appropriate breakload values. This would eventually cause low blind rivet performance or failure. The wire size and coating also have an affect on the tensile strength and shear strength, as well as the fit, function and shelf life, all of which are critical points in the IFI specification. Since RivetKing tensile tests every wire batch we receive, we are able to collect valuable information and provide it directly to our production staff for use with our drawings and in production. please turn to page 208