DN Staff

September 23, 1996

5 Min Read
Focus on fasteners

Hand on, tool off

Concordville, PA--Normally, captive screws used in applications that require repeated access are both tightened and loosened by hand. Some applications, however, demand restricted access, with UL standards calling for a "tool-removable" door or cover.

Removal of hand-tightened SentinelTM panel fasteners requires a slotted, Phillips, or multi-lobe drive tool. If a technician tries to loosen the screw by hand, its head merely ratchets in the opposite direction without disengaging the screw thread. The captive screw meets both UL 1950 and EN 60950 specifications for "service access."

Southco, Inc.

No loose hardware

Danboro, PA--Vehicle manufacturers and their suppliers often specify dog point studs to provide a lead in during nut assembly, and to protect the first thread of the stud during nut engagement. That's why a stainless steel, self-clinching stud, with a specially designed dog point, is currently used in the assembly of airbags for several European OEMs.

Designed to perform in 1mm-thick stainless-steel panels, the flush-head stud offers all the benefits of other self-clinching fasteners: Displaced host material around the mounting hole cold flows into an undercut beneath the head, making the fastener an integral part of the assembly, while a serrated clinching ring prevents rotation.

Penn Engineering and Manufacturing Corp.

Trib joints simplify design

Braintree, Essex, UK--Conventional methods of fastening a pinion, cam, hub, or flange to a shaft include threading, gluing, pining, welding, brazing, or a combination of these techniques. Now there's an alternative: Trib joints (from tribology) raise the end product's torsional and tensile strengths, but lower preparation, assembly, and finishing costs.

The patented process is straightforward. First, coat the mating surfaces until sufficient mechanical coupling prevents further movement. The anti-lubricant scavenges the oxygen as rubbing asperities--high points of the irregularities that make up the microscopic surface--deform. Absence of the oxide layer, which acts as a lubricant, causes the parts to seize up with predictable force.

Trib joints can be formed from soft and hard steel, stainless steel, aluminum, cast iron, and sintered metals. Mating parts need not be similar; the only requirement is an interference fit. Trib Tech Group Ltd.

Corrosion-free rivets

Shelton, CT--Matching a stainless-steel mandrel to an aluminum body rivet gives Multi-Grip TM blind rivets from POP Fasteners (R) great corrosion-resistance with a grip range to 3/4-inch. Applications? Anything from autos, trucks, or trailers, to lawn mowers and metal buildings. A new 1/4-inch-diameter also is available.

Like all Multi-Grip blind rivets, the stainless steel/aluminum design offers greater radial expansion than ordinary rivets, making it less sensitive to hole size. And because the mandrel head is locked in, but not totally encapsulated, it eliminates the rattle of standard open-end products.

Emhart Fastening Teknologies

Goodbye galling

Rockford, IL--As manufacturers of head-disk assemblies and computers can testify, inserting stainless-steel fasteners into stainless-steel engagement materials can lead to galling.

Camtronic(R) galling-resistant fasteners overcome this problem by using a higher-strength stainless steel. Developed through proprietary manufacturing techniques, the special alloy is sufficiently different from traditional 302 or 303 stainless steel with regard to hardness and other properties, that seizing should no longer be a concern.

Furthermore, Camtronic fasteners are available with the Torx Plus(R) Drive system, which designs out debris by eliminating the recess damage that can occur with Phillips or hex heads. Anything else? Yes. Camtronic fasteners that undergo the Microtech(R) finishing process meet class 100 cleanliness standards for clean room assembly.

Camcar Textron

Draw together, hold tight

Redditch, Worcestershire, UK--ProLatch TM not only functions as a normal draw latch, it also closes a door or panel against a seal or gasket to hold it firmly in place. An integral safety catch keeps the surface-fitting fastener in the closed position; another version accepts a padlock. Applications: machine guards, hinged doors, and industrial cabinets.

Protex Fasteners Ltd.

Intelligent screw

Combs-la-ville, France--The "intelligent screw" yields torque measuring precision of better than plus or minus 8% error, compared to plus or minus 20% for existing methods.

A strain sensor, glued to the screw head, incorporates a thin layer of glass containing tiny metal particles. When tightened, the head naturally deforms, bringing the metal particles closer together. This, in turn, changes electrical resistance measurably.


Rivet/screw hybrid

Parsippany, NJ--Reuseable Rivscrews(R) install like rivets, remove like screws. Simply place the fastener through the prepared hole in the component and into the accepting material. As the high-speed tool pulls the mandrel through, the Rivscrew expands into the surounding material. Installation forms a domed head achieving high clench and secure clamp up. The mandrel action also leaves a hexagonal bore allowing removal with a standard key.

Avdel Corp.

Sign up for the Design News Daily newsletter.

You May Also Like