BUTTRESS THREAD CUTTING METHOD ON END PORTIONS OF CASING TUBES AND COUPLINGS Russian patent published in 2007 - IPC B23G1/00 

FIELD: rolled tube production, working of seamless hot rolled casing tubes.

SUBSTANCE: method comprises steps of cutting buttress thread with pitch equal to 5.08 mm at four passes. In order to prevent or to decrease degree of self- unscrewing of large-weight columns while keeping torque values at joining tubes and couplings and providing improved fluid-tightness of threaded joint, threading is realized on tubes and couplings at different roughness degree of thread side surfaces. Dents, indentations and leading sides of thread of tubes and couplings are worked at surface roughness Ra no more than 3.2 micrometers while opposite sides of thread of tubes and couplings are worked at roughness Ra = 10 - 15 micrometers.

EFFECT: improved quality of threaded joints.

1 dwg