A diverter or rotary drill head has a rubber stripper assembly mounted to a stinger flange. An annular retaining collar is releasably received within the upper marginal end of the drill head main body. the retainer collar is axially spaced from a shoulder formed on the main body to form an annular area therebetween within which the stinger flange is rotatably received in low friction relationship. The retainer collar is held in assembled position by a plurality of retractable radially spaced dogs. The dogs are retracted to permit the stripper rubber, stinger flange, and stinger to be lifted free of the main body. This enables repairs to be rapidly and economically effected on the rotating parts of the diverter and provides a seal means by which well blow-outs can be diverted away from the drilling rig.