... a professional manufacturer of API 11B sucker rod couplings, including Spray Metal coupling, class T coupling, Sub OD coupling, with ... Hole, grand chamfer, Two-way camber, etc. With world top level equipments and technicians, the monthly production capacity is more ... -SPANAt least 6 monthsBASIC HARDNESS HRC 16-23SURFACE HARDNESS AFTER SPRAY WELDINGHRC 56-62, ≥ 480 HV0.2THREAD STANDARD ROLLER THREAD ...