Abstract: At an injection-molding machine, an assembly for clamping a mold half to a platen comprises a bore therein and a projection on a substantially planar face of the mold half. The projection includes an annular flange insertable into the platen bore and an annular groove defined in part by an inclined or beveled surface of the flange. A pair of sliding plates are reciprocatably mounted in the platen for shifting from withdrawn positions inwardly to locking positions, the plates having beveled inner edges for coacting with the inclined flange surface to clamp the mold half to the platen. The bore is advantageously formed with a conical extension for accepting the head or nozzle of an injection device or extruder. Another mold half may be clamped in an analogous manner to another platen provided with a bore and reciprocatably mounted locking plates, the two platens being shiftable relatively towards each other.