Spring-steel fasteners

Figure 12.5. Types of nut (a) wing (b) dome or acorn (c) rivet bush or nut(d) blind (e) flat spring steel fastener and (f) J type fastener...

Spring-steel fasteners are available which as well as holding also provide a locking action. If access is available from both sides, a flat nut can be used. Fig. 12.5(e), or from one side a J-type nut can be used, Fig. 12.5(f). In their natural state these nuts are arched, but they are pulled flat when the screw is tightened. 

Other Mechanical Fasteners. Push-on spring steel fasteners can be used for holding Ught loads. They are used when low-cost, rapid mechanical assembly is required. Spring steel fasteners are also often referred to as speed nuts and speed clips. 

Spring steel fasteners are simply pushed over a molded stud with hand pressure. A simple push-on spring steel fastener is illustrated in Figure 7.10. The stud should have a minimum 0.38 mm (0.015 in) radius at its base. Too large a radius could create a thick section, resulting in sinks or voids in the plastic molding. 

Spring steel fasteners are usually made from close annealed carbon steel strip, and after being formed are hardened and tempered. A conventional sheet metal screw or self-tapping screw is used with the basic type of spring steel fastener, which has an arched base and two arched prongs (Fig. 5). 

Fig. 5. Spring steel fasteners in operation showing the double lock action. (Courtesy of Firth Cleveland Fasteners Ltd.)...

Fig. A.5 The base-plate is shown in (a) with the tourniquet belt slot indicated with the red arrow, the base-plate (bl) and cinch-assembly (b2) are shown together in (b) where b2 fit into bl and secured with the shoulder mounted screw-fasteners and the spring-steel stop-plate (red arrow) for controlling the travel of the cog-wheel containing the grasping spikes the reverse side of the cinch-assembly riveted to the top section and detailed in (d) that shows the contact between the stop and cog-wheel...

Push-on spring-steel — Molded stud fastener ... 

The rotating autoclave shown is a vessel formed by boring out the steel core of a 6-inch high-explosive shell until the thickness of the wall was about 1 9 cm. The steel cover, which is of similar thickness, is fastened down with twelve bolts and rendered gas-tight with a lead washer. The cover carries a powerful adjustable spring safety-valve,... 

Figure 5.27 shows a finite element model of the joint. The members are modelled by 8-node Serendipity elements under the assumption of plane stress conditions. The two steel plates of thickness h are modelled by one steel plate of thickness 2h for an accurate overall stiffness representation. The fasteners and holes are represented by Unite spring elements which are connected to node points on the members. The stiffness constants of the spring elements (Kffe) are determined according to the procedure described in section 5.2.2.4 of the EUROCOMP Handbook. 

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