BigHead TwinDisk

BigHead’s latest fastener - the TwinDisk – is designed specifically to overcome the problem of providing a strong, easy-fit fastening in composite or laminated lightweight panels.

As our pictures show, the basic design consists of two 316 stainless steel disks, welded centrally to both ends of an internally-threaded stainless steel collar. The disks are 1.2mm thickness 316 stainless, and are welded using BigHead’s uniquely sophisticated weld technology.

The use of composite panels and structures in the Aero, Auto, Marine, Construction and other core industries and applications is growing rapidly. These new materials, utilising carbon fibre, GRP, glassfibre, thermoplastic and alloy outer skins, consist of a core material – in honeycomb, block, foam or solid – bonded to outer skins of a different material.

The stainless steel TwinDisk, with its simple, strong design and unique BigHead weld technology, provides a rapid and efficient fastening point anywhere in a structure.

TwinDisks are installed by cutting a hole through the panel’s top skin, wide enough to take the lower disc’s 30mm diameter. Depth of cut is adjusted to remove all core material (aluminium, polythene or fibre honeycomb or other solid/foam materials) down to the bottom, inner ‘skin’ of the panel. BigBond’s 2-part FS Acrylic adhesive is then applied liberally to the bottom surface, and the assembly pressed firmly down into the cavity (an optimum 1mm thickness of adhesive is recommended between the inner skin and the bottom of the Twindisk).

The surplus adhesive is forced through the holes in the disc, and provides an immensely strong anchor for the load-spreading bottom disk. The top disk can be installed flush with the top ‘skin’, or inset as required. It is recommended that the supplied stud remains fitted to the TwinDisk during assembly - complete with the supplied plastic sheath - to prevent the thread being fouled by any surplus resin or adhesive.

The FS Acrylic has a cure time of up to 24 hours to achieve 60% of design strength; 100% takes up to one week and achieves a tensile adhesion of up to 4000 lbs/sq. in., dependent on the skin material.

The TwinDisk Extra incorporates a specially-adapted top disk of 40mm diameter. This permits a rebate cut and glue into the top ‘skin’, to give enhanced grip and load- spreading performance, as well as a more even distribution of applied shear and tensile loads.

Both versions of the new fastener are available with either an M6, M8 or M10 internal thread. Standard headless threaded studs are 40mm long. TwinDisks are manufactured in overall heights of 15mm, 20mm or 30mm; they can also be made to a height suitable for a specific panel thickness as required, at extra cost.