FALL 2019

68 THE DISTRIBUTOR’S

68 THE DISTRIBUTOR’S LINK Anthony Di Maio Anthony E. Di Maio attended Wentworth Institute and Northeastern University. In 1962 he started working with Blind Fasteners as Vice-President of Engineering & Manufacturing for two blind rivet manufacturers. He has been Chairman of the Technical Committee of the Industrial Fasteners Institute (IFI) and is still involved in the writing of IFI specifications. In 1991, he started ADM Engineering and is working with Fastener Manufacturers developing new fasteners and special machinery. He can be reached at ADM Engineering, 6 Hermon Ave., Haverhill, MA 01832; phone and fax 978-521-0277; e-mail: tdimaio@verizon.net. PROPER HOLE CONDITIONS FOR BLIND RIVETING Work piece hole conditions can affect the performance of a blind rivet. Many times a blind rivet user will contact me that they are having a problem with their blind rivets setting properly. In many cases, it is not the blind that is causing their problem, but instead it is the condition of the hole in their work piece that is causing the problem. The following are some of the hole conditions that will give a blind rivet user a problem. Hole Burrs This condition occurs when drilling a hole with a dull drill and pushing the drill through the work piece rather than having the drill cut the material. A sharp drill should always be used when drill a hole for a blind rivet. A dull drill will cause a circular burr to be formed around the diameter of the hole. This condition can be created in a work piece made of any type of metal. A worn or dull hole punch will also leave a burr around the diameter of the hole to be riveted. In most cases, the burr is on the blind rivet upset side of the work piece because the drilling operation is usually performed from the operator side. Burr Break Away Upset Side tensile strength, the burr cuts into the blind rivet barrel upset. If the blind rivet body is made of aluminum and the work piece is made of steel, stainless steel or hard aluminum, the burr will cut away a portion or the entire barrel upset created by the mandrel head when setting the blind rivet. When a part of, or the entire upset is cut away when setting the blind rivet, this greatly reduces the tensile strength of the set blind rivet. To achieve the tensile strength of the set blind rivet, there must be no burr on the hole either on the upset side or the flange side of the work piece. The upset side burr will cut the blind rivet barrel upset and on the flange side it will cut the flange of the set blind rivet. Hole Diameter The diameter of the hole to be riveted is also important relative to the tensile strength and clamp load of the set blind rivet. All blind rivet manufacturers list the recommended minimum and maximum hole diameters for all sizes of blind rivets they produce. The minimum is not the problem. If the hole diameter is too small the body of the blind rivet will not entire the hole. The oversized hole is the problem for more than one reason. Flange Side FIGURE 1 FIGURE 2 When the blind rivet is inserted into the hole of the work piece and set, the mandrel head upsets the barrel of the blind rivet body and forms the barrel against the burr. As the mandrel is being pulled to it’s maximum CONTRIBUTOR ARTICLE When a blind rivet is set in an oversized hole, the mandrel head will pass through the barrel of the blind rivet body. The mandrel will continue down the blind rivet body until it teaches the flange of the blind rivet body. CONTINUED ON PAGE 146