Radial and Orbital Riveting Add Finesse to Fastening, Joining

An EcoLine orbital riveter from Baltec uses 2 to 7 bar of pneumatic pressure to form heads on rivets. Maximum riveting force ranges from 20 kN on the Model 20 to up to 35 kN with the Model 35.

Orbital forming is a cold-forming process used on parts in which an angled peen or forming tool attached to a spindle spins 3 to 6 degrees off center and applies axial and radial forces to a portion of a part. This progressively moves some of that material, forming it into a predetermined shape.

The process works on a wide variety of malleable materials, including steel (even high-alloy steel with a hardness of 54), aluminum, brass, bronze, copper, lead, and zinc, as well as many polymer composites and other plastics, including ABS. Depending on the tool, the process can create swages, crowns, and flares, or, as it is most commonly used, put heads on studs and rivets (also called upsetting or bucking rivets).

Peens are shaped with the final shape of the finished part in mind. Specific peens have been designed to produce conical, flat, eyelet, and crown heads. The forming tools are usually made of M2 drill-rod steel and heat treated to a Rockwell C hardness of 60 to 64. On the riveting or forming machine, they are held in place by a setscrew and can be quickly changed.

In orbital riveting, also called radial or spin riveting, the forming tool is in contact with a small area on the part being formed at any one time. As a result, the compressive forces on it are 80% less than in impact riveting, a brute-force approach to riveting. The line of contact between the tool and rivet does not vary.

On each revolution of the spindle, the same line of contact is maintained. Because the same point on the tool is always in contact with the same point on the rivet, there is little friction and no tearing of the material. This means it will not create a galled or hammered finish. Solid rivets formed with orbital riveting will have smooth finishes whether they are crowned, conical, or flat head.