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Semi-Tubular Impact Riveting

The most common type of impact riveting is semi-tubular impact riveting.

The semi-tubular rivet was invented and patented in 1876 by American engineer and manufacturer, Melon Bray. The intention was to create a fastener similar to the solid rivet that required much less insertion force and allowed longer rivets to be used without buckling of the rivet shank.

A semi-tubular rivet, by definition, is a rivet with a hollow end whose hole depth does not exceed 112% of the rivet body diameter. (A tubular rivet is any rivet whose hole depth is greater than that.)

Semi-tubular rivets are inserted in the same basic manner as solid rivets. The way the rivet is formed and its affect on the parts being assembled, however, are quite different.

In semi-tubular impact riveting, a compressive axial load is applied to the end of the tubular rivet shank with a specially shaped form tool. This causes the rivet end to flare as it follows the shape of the tool.

The rivet end continues to flare and roll until the end has rolled back against the surface of the workpiece.

The parts being assembled are (typically) slightly compressed under this load. Most of the joint strength is compressive between the rivet head and rivet clinch (formed end). Rivet shank expansion, like that required for successful solid impact riveting, is minimal. Rivet insertion force is typically less than 40% of that required for a solid rivet of the same shank diameter & material.

SEMI-TUBULAR RIVET DIMENSIONING

The following charts are design aids to assist you in standard rivet sizing:

These charts coincide with ASME/ANSI standard #B18.7 - 1972 (R1992).

More detailed info on standard rivet dimensioning and tolerancing can be found from a number of sources including:

ANSI (American National Standards Institute - http://web.ansi.org/)

ASME (American Society of Mechanical Engineers - http://www.asme.org/)

IFI (Industrial Fasteners Institute - http://www.industrial-fasteners.org/)

SEMI-TUBULAR RIVETING RULES OF THUMB

While actual rivet sizing will be very dependent on the application's conditions of use, there are a number of "Rules of Thumb" that have been developed over the years to help determine a good starting point when sizing a rivet. Here are a number that we've picked up along the way:

Rivet Clinch Allowance: Rivet clinch allowance is normally between 50 and 65 percent of the nominal rivet shank diameter.

Rivet Clearance Hole Diameter: In general, the rivet clearance hole should be between 105 and 110% of the maximum rivet diameter. When dealing with applications where multiple rivets are being used, this is often increase to between 110 and 115% to account for potential tolerance stack-up problems.

Rivet Diameter to Part(s) Thickness Ratio: The ratio of a semi-tubular rivet's shank diameter to total material thickness should optimally be:

Metal parts: Between 1:1 and 3:1
Plastic parts: 1:1

Rivet Edge Distance: The minimum recommended distance from the centerline of a rivet and edge of the work piece is 2.0 x Rivet Shank Diameter.

Pitch Distance of Multiple Rivets: The center-to-center distance between rivets on metal applications should be at least 3 times the largest rivet diameter being used. For plastics, this distance is increased to 5 times the largest rivet diameter.

Rule of Thumb for Size of the Clinched Rivet End is as follows (these estimated dimensions are for reference only):

Clinch diameter = 1.50 x Rivet Shank Diameter
Clinch height = .20 x Rivet Shank Diameter

Hopefully, the above information will help you with your semi-tubular riveting application. Please contact us directly for further assistance.

Jay-Cee Sales & Rivet

"The Quality Rivet People"
For further information please call 1-800-521-6777
www.rivetsinstock.com   sales@rivetsinstock.com