A hot runner apparatus for a mold assembly of an injection molding machine includes a hot runner plate assembly having a first end portion and a second end portion and a machine axis extending therebetween. At least one insert coupling having an axial bore is secured to the first end portion of the hot runner plate assembly, for separable sealed engagement with a gate insert affixed to a cold half of the mold assembly. The insert coupling includes a coupling interface for contacting a mating interface of the gate insert in sealed contact during an injection cycle of the injection molding machine. The coupling interface includes a primary side surface that is inclined relative to the machine axis.