In a narrower aspect, the invention resides in a bolted joint in which the bolt is engaged by the aperture. The invention has particular utility in relation to the assembly of structural frames such as light gauge steel roof trusses, wall frames, ceiling frames, and floor frames.

BACKGROUND ART It is well known to fix two or more members together by forming aligned apertures in the members and inserting and fastening a bolt through the aligned apertures. Typically, in order to facilitate easy insertion of the bolt through the apertures, the bolt is received in the apertures in a clearance fit, and thereafter the bolt and nut are inter-engaged and tightened to compress the two or more members together. Typically also, both the tip of the bolt and the lead-in of the bore of the nut include a chamfer to assist alignment of the bolt with the nut during initial inter-engagement of the bolt and nut.

A drawback with the fact that the bolt is received in a clearance fit within the apertures is that, under load, the members are able to move in a shearing direction a small distance relative to one another, the distance being dictated by the magnitude of the clearance between the bolt and apertures. Thus, the

clearance, which positively facilitates insertion of the bolt and general assembly, negatively compromises the rigidity of the final assembled structure.

SUMMARY OF INVENTION According to one aspect the invention resides in a method of engaging a bolt with an aperture, the method including :- forming an aperture having a flare ; compressing said flare between the head of a bolt and a nut, said compression causing flattening of said flare such that the effective dimension of the aperture is reduced.

Preferably, the flattened flare engages the shaft of the bolt. Preferably also, the underside of the nut does not have a chamfer to lead in the tip of the bolt to the bore of the nut.

According to another aspect the invention resides in a method of forming a bolted joint between two or more members, the method including :- forming an aperture having a flare in at least one of the members; compressing said two or more members together between the head of a bolt and a nut, said compression causing flattening of said flare such that the effective dimension of the aperture is reduced.

Preferably, the flattened flare engages the shaft of the bolt. Preferably also, the underside of the nut does not have a chamfer to lead in the tip of the bolt to the bore of the nut.

In other aspects the invention resides in a bolted joint, and in a structural frame such as a roof truss, wall frame, ceiling frame, floor frame or the like including such a bolted joint.

BEST MODE The invention will now be described with reference to an example for illustrative purposes.

FIG 1 is an exploded section view of a bolted joint prior to assembly; FIG 2 is an exploded perspective view of the bolted joint prior to assembly and with part of the front member cut away for clarity ; and FIG 3 is a section view of the bolted joint after assembly.

With reference to Fig 1 there is shown the exploded section view of the bolted joint according to the present invention. As can be seen, each of the planer members 10,12 includes a flared aperture 14 which is generally frusto-conical in shape.

In the illustrated embodiment, the flared aperture is formed by firstly punching an 11.5mm hole and thereafter flaring the hole so that it assumes an enlarged diameter of 12. 5mm.

The bolted joint also includes a bolt assembly consisting of a bolt 16 and nut 18.

In the illustrated embodiment, the diameter of the thread on the shaft of the bolt 16 is 11.7mm. As such, it is received in a clearance fit within the expanded or flared aperture 14 which as mentioned above has a diameter of 12. 5mm.

As can be best seen with reference to Fig 2, both planer members 10,12 have flared apertures 14. Note that the frontal planer member is partially cut away for clarity. The flares both extend in the same direction and are tapered so that the planer members 10,12 can nest together prior to tightening of the bolt. Note also, that the underside of the nut 18 is flat and the lead in section of the bore of the nut does not include a chamfer which would assist in leading in the tip of the bolt 16.

It will be understood that as the bolt assembly is tightened, compressive forces are applied to the flared apertures 14 such that the flares are flattened with a resultant decrease in diameter of the apertures. As the effective dimension or diameter of the apertures 14 is decreased under compression, the material forming the flared perimeter or upturned lip of aperture 14 is preferably urged into engagement with the thread on the shaft of bolt 16. Materials and dimensions may be selected such that the material is forced to flow in a plastic manner between adjacent threads on the shaft of bolt 16. This feature is shown in Figure 3.

The reason that the underside of the nut 18 (more specifically the lead in section of the bore) does not have a chamfer is because the presence of a chamfer would provide a void into which the material forming the flared perimeter or upturned lip of aperture 14 could flow. The absence of the chamfer ensures that the material is urged into engagement with the thread of the shaft of bolt 16.

Once the bolt assembly has been tightened as shown in Fig 3, the shaft of the bolt is effectively held in an interference fit with planer members 10,12. Thus, the resent invention retains the advantage of having a clearance between the bolt and aperture during assembly thereby facilitating insertion of the bolt into the aperture

and facilitating assembly generally. However, the tightening process eliminates or at least reduces the clearance thereby enhancing the rigidity of the final assembled structure (eg roof truss or the like).

It will of course be realised that whilst the above has been given by way of an illustrative example of this invention, all such and other modifications and variations hereto, as would be apparent to persons skilled in the art, are deemed to fall within the broad scope and ambit of this invention as is herein set forth.