Considerations for Permanent Part Assembly

Comparing Permanent and Nonpermanent Fastening Methods

	Joint Characteristic						Cost
	Articulation	Clamp load	Low profile	Vibration resistance	Hole fill	Aesthetics	Fastener	Machining	Equipment	Labor	Overall
Tenon + orbital or spiral forming	Best	Good	Best	Fair	Fair	Best	Best	Fair	Good	Good	Good
Tenon + hot upset forming	Poor	Best	Best	Best	Best	Fair	Best	Fair	Poor	Good	Good
Solid rivet + impact riveting	Poor	Fair	Best	Good	Best	Good	Good	Best	Fair	Best	Good
Semitubular rivet + impact riveting	Good	Fair	Best	Fair	Fair	Good	Good	Best	Good	Best	Best
Rivet + orbital or spiral forming	Best	Fair	Best	Fair	Fair	Best	Good	Best	Good	Good	Good
Rivet + hot upset forming	Poor	Best	Best	Best	Best	Fair	Good	Best	Poor	Good	Good
Bolt and nut, formed	Poor	Best	Fair	Good	Poor	Poor	Poor	Best	Fair	Poor	Fair
Bolt and nut	Fair	Best	Fair	Good	Poor	Poor	Poor	Best	Good	Fair	Good
Stud and nut	Poor	Best	Fair	Good	Poor	Fair	Poor	Good	Good	Fair	Fair
Screw	Poor	Good	Best	Fair	Poor	Good	Fair	Good	Good	Fair	Good
Retaining ring	Best	Poor	Poor	Poor	Poor	Good	Poor	Best	Best	Poor	Good
Cotter pin	Best	Poor	Poor	Poor	Poor	Poor	Poor	Best	Best	Poor	Good

Every application is different, and there is no “one size fits all” solution for permanent part assembly.

This matrix rates permanent and nonpermanent fastening processes for various joint requirements. For these ratings, we examined the lowest cost and least number of machining steps to achieve the requirement in the simplest way possible. For example, a low-profile joint can be achieved with a countersink or counterbore—at the cost of extra machining. Similarly, aesthetics are greatly determined by the type of fastener and its coating or finish, which greatly impacts its cost. A retaining ring or cotter pin is a more expensive fastener, compared with a rivet, especially if that cost includes a mating pin with a groove or through-hole. Overall cost considerations include the fastener, machining, equipment and utilities, and labor costs.

All cost estimates are relative to each other across processes. For example, a tenon has no fastener, and therefore, no fastener cost relative to a rivet or bolt, but a machined tenon has a greater machining cost than a through-hole for a rivet or bolt. A tenon formed as a casting would result in a different costing analysis.

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Sean S. Cumming is the Business Development Manager for Orbitform Group, Jackson, MI. He can be reached at scumming@orbitform.com.

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