Process for the manufacture of a two-part operating piston for a disc brake

Claim 1

A process for permanently joining a cylindrical core of a heat-insulating material to a metallic beaker-shaped part having a central axis, an outer end portion, an annular outer end surface on the outer end portion and a bore therein with an outer open and for receiving the core to form an operating piston of a hydraulically operated disc brake, comprising: inserting the core axially into the bore of the beaker-shaped part and providing a small clearance between the bore and the outer cylindrical surface of said core; providing out outer end portion on said core protruding axially outwardly beyond the annular outer end surface of the beaker-shaped part and having an outer end surface thereon; providing a frustoconical surface on said outer end portion of the core extending from a position on said outer end surface on sia core radially inwardly of the outer cylindrical surface thereof to the outer cylindrical surface proximal said outer end portion on the beaker-shaped part; and plastically deforming part of said outer end portion of the beaker-shaped part radially inwardly into engagement with said frustoconical surface by applying to said annular outer end surface a rotating pressure tool having an asymmetric wedge-shaped cross section thereby forming at least one wedge-shaped recess in said annular outer end surface having a radially inner flank extending substantially parallel to said frustoconical surface and a radially outer flank extending substantially parallel with the central axis of the beaker-shaped part.