the collapsible mold segments in the extended position the part shown will be more fully understood upon reference to fig6 8 to be subsequently described the operation of both collapsible core assemblies is identical and is symetrical on both sides of the parting line between core assemblies 24 and 26 for this reason fig3 illustrates only the operating mechanism for right hand core element 26 collapsible core assembly 26 is mounted upon rod 27 which is connected to conventional hydraulic cylinder 28 for movement in a reciprocating manner when so moving the core section rides upon slides 29 and 31 slides 29 and 31 are mounted respectively on supports 32 and 33 which in turn are fastened to base plate 34 of the molding machine fig5 shows a plan view on line 5 5 of fig3 showing the molding apparatus of this invention and in particular the end view of collapsible core 24 except for this collapsible core the features shown are conventional and include the lower outer mold form 36 and the upper mold 37 plastic supply conduit 38 is connected to gate 39 through which the plastic is injected into the mold conventional ejector pins 40 and 41 are provided to eject the part from the mold upon upward movement of mold section 37 the above description sets forth the major components used to produce the part with the 360 u00b0 recess and attention is now directed to fig6 and 8 which most clearly illustrate the novel features of my invention fig6 and 7 show the collapsible assembly core with a plurality of retractable mold segments in the extended or molding position the mold segments comprise small segments 42 43 and 44 and large segments 45 46 and 47 these retractable mold segments are positioned between a.