the shaft between a position where this needle is exposed as shown in fig4 to a locking position where the guard member is moved forward as shown in fig9 to cover the tip 42 of the needle element after the molten polymeric material is injected into the cavity it cools and shrinks to firmly bond the locking element 44 to the needle shaft because a substantial portion of the exterior surface of the needle shaft is in intimate contact with the locking element 44 a secure bond is formed which is highly unlikely to rupture thus the locking element 44 and needle shaft are safely attached to one another so that bond rupture is virtually eliminated moreover the use of costly adhesives in securing the locking element 44 to the needle shaft is eliminated the locking element 44 includes a locking section 50 similar to that described in above identified patent applications and includes a pair of shoulders 56 and 58 separated by an annular recess 60 which captures collar elements 62 and 64 of the guard member 48 when the guard member is moved to the forward position covering the tip 42 of the needle element 40 the stem 52 is essentially an elongated hollow cylindrical member extending between the locking section 50 and the hub 54 the open spaces a and b in the body of the stem result from the pins not shown extending into the mold cavity and grasping the needle shaft the hub 54 includes a connector piece 66 having an internal cavity 68 formed by an inwardly tapering wall 70 which terminates in a.