Understanding Rivet Dimensions - Lightning Bolt, Inc.

Understanding Rivet Dimensions:  A Simple Primer

Understanding rivet dimensions means realizing a rivet’s diameter and length measures differently from that of a hex bolt.  I will explain the very basic mechanics of a rivet assembly and the rhyme and reason behind the two numbers denoting the size of a rivet.

Rivets join two materials. A drilled hole in both the materials accommodates the rivet. In turn, the rivet holds the two materials together.  The rivet passes through the holes in the two materials and a rivet setting tool finishes the install.  The tool pulls the two materials together and expands the body of the rivet on the blind side, or the side that cannot be seen. The mandrel continues into the body of the rivet, filling the hole and completing the expansion. The mandrel breaks, leaving a solid circle lock that ensures a weather resistant assembly. This assembly will also be vibration-proof and extra strong. Rivets in a pair of jeans exemplifies a simple rivet application.  Those in the body of a car, ship, or airplane mark a more complex rivet application.

I will explain the very basic mechanics of a rivet assembly and then  the rhyme and reason behind the two numbers denoting its size.

The first dimension notes the diameter and the second notes the length, or the grip range.  The rivet diameter measures in 32nds of an inch. If the size of the hole measures 3/16, the size would be termed as 6 for 6/32. The grip range is the total thickness of the materials being fastened together. Grip range measures in 16ths of an inch. Therefore, if the second number of your rivet size is 4, this means the grip range measures 4/16 of an inch (1/4).  A 4-4 All Aluminum Dome Blind Rivet means the rivet diameter is 4/32 or 1/8, the grip range is 4/16 or ¼, both the rivet and the mandrel are aluminum and the head style is dome.

In the above example, the material and the head style were noted.  Common rivet materials are:   aluminum, steel, stainless steel, or copper. A rivet should match the mechanical and physical properties of the materials being joined.  This holds true especially for assemblies working in high temperatures and/or corrosive elements. This compatibility helps reduce the risk of galvanic corrosion and material fatigue. The rivet and the mandrel can be the same material, or they can be two different ones. In addition, there is also the head style to consider: open end, closed end, dome, countersunk, multi-grip, etc…

A blind, or a pop rivet, ranks as the most commonly used type of rivet.  Pop rivets work in assemblies where only one side can be reached.

Years ago, prior to the invention of the blind rivet in 1916, one had to hammer at the rivet from both sides of the work. Now special rivet guns complete the work from one side.

I hope this helps those of you with little familiarity with rivets. Wrapping it all up, just remember the first dimension refers to the diameter (just like a bolt). The second dimension refers to the to the thickness of the work (grip range).


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