It is known to fasten build-on parts of various types, for example different switches, to steering wheels. In this context, in practice, each vehicle manufacturer has his own ideas regarding the type and mounting location of the build-on parts. Since a steering wheel manufacturer will as far as possible like to satisfy the various requirements by means of existing steering wheel skeleton structures for reasons of cost, he has two possibilities for making these structures practicable.
One possibility is to mount domes, straps and other devices for the fastening of build-on parts to a steering wheel onto the existing skeleton structure at a later stage by means of die changes. The disadvantage of this procedure is that changes are possible only via a 3-D model. The original skeleton die, that is to say the mold for producing the skeleton, has to be dismantled for the change and the mold has to be modified by erosion, for which purpose a new electrode has to be made. Furthermore, it is necessary, after the change has been concluded, once again to carry out a free-testing method. This procedure results, overall, in high additional costs. A further disadvantage is that, as a result of the accumulation of material at the spokes due to domes and straps, the bending strength of the steering wheel skeleton is adversely influenced.
The second possibility is to drill into the steering wheel skeleton, for example in the region of the spokes, in order to screw on build-on parts there. The disadvantage, here, is that the strength characteristics of the aluminum or magnesium skeleton are impaired, above all, during drilling into the spokes. This increases the risk that a spoke fracture will occur in the event of a crash.