Machine Design

Self-Piercing Fastener Installs In One Step

Twist-Tack metal fasteners from Amtak Fasteners.

Self-piercing fastener installs in one step

Twist-Tack metal fasteners from Amtak Fasteners, East Providence, R.I. (, reliably attach materials such as rubber, plastic, and thin-gauge aluminum to steel tubing, aluminum extrusions, and lightweight metal castings. They do not require predrilled holes for installation and generate hundreds of pound of withdrawal resistance after set in place with a compression riveter, impact air tool, or the company's bench press.

During installation, the fastener itself punches a hole in the material being attached, then forms an anchor cone in the base metal. Installation is complete when the knurled section of the Twist-Tack engages the anchor with a cutting, twisting, and wedging motion. The fastener design has passed a 120-hr salt-spray test that meets ASTM B117 specifications. The fasteners have been successful in several tubing products, including ladders, outdoor furniture, and signs.


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