TechArchive

Original article date: July 2000

Looking for a cost effective alternative to weld nuts? Alan Quinn reports on the Kaptinut

There are many alternative captive fasteners available for the sheet metal industry, each with its own benefits and disadvantages. The Kaptinut is a cost-effective alternative to weld nuts in high volume automotive, appliance and other sheet metal applications.

Weld nuts suffer from a number of disadvantages, including:

• Weld splatter
• Distortion of the panel owing to heat, with ever thinner panels exacerbating the problem
• Unsuitable for use on plated panels
• Creation of noxious fumes
• Additional cost and inconvenience of a secondary operation
• There is no easy method of telling if the weld has taken successfully.

The Kaptinut is a high strength, captive threaded fastener system – a range of nuts permanently attached to a panel or component by a mechanical process which requires no heat, electricity, chemicals or adhesives. They are ideally suited to multiple and automated insertion into thin gauge steel, aluminium and pre-finished materials. Kaptinut can offer substantial improvements to product quality whilst reducing in-place costs.

Kaptinut fasteners are available in ISO metric coarse pitch series thread sizes from M4 to M10 and the finished nuts conform to the mechanical properties required for a BS3692 Grade 8 nut.

The finished installation allows for visual inspection, ensuring product quality and confidence at all stages of manufacturing. Kaptinuts can be assembled from either side, as “pull-through” strength is comparable to “push out” strength. This improves flexibility of manufacture.

Installation is a simple, single stroke pressing operation. The nut can be manually fed on a basic fly press or there can be fully

automated multiple insertions within a multi-stage progression tool and press. Overall volume and economies will dictate the best options, but installing the fasteners at the same time as manufacturing the components offers considerable cost-saving opportunities by eliminating the need for a second operation. As the nut installation forms the component, it introduces rigidity into the component and the fastening, resulting in higher bending moment. A near-flush finish is achieved on one side of the component and the fasteners can be plated before or after installation.

Other benefits include:

• Square nut/4 spline design – a square nut in a round hole – enabling optimum material flow between splines and therefore high torque resistance.
• Rolled internal threads which provide higher strength than traditional cut threads
• Modular die design, enabling material thicknesses up to 3.5mm to be accommodated using only one die body
• Zero defect quality designed into the manufacturing process using state of the art six station nut forming and thread forming machines, capable of producing up to 500 nuts per minute
• Low cost automated feed systems.

There is only one nut for each thread size. Varying the tool die accommodates variances in component thickness, thus minimising stocking requirements.

• Kaptifast