Patent ID: 6174000
Filing Date: 2001-01-16
Classification: E21B,F16L

Abstract:
A threaded joint for oil well pipes which comprises an oil well pipe having a male thread of a trapezoidal thread with a taper and a coupling member having a female thread of the trapezoidal thread with a taper,wherein t (thickness of said pipes)/D(outer diameter of said pipes) is not larger than 9%, and a load flank angle .theta.1 of said trapezoidal thread is a range of 0<.theta.1.ltoreq.3.degree.,wherein said trapezoidal thread has a shape such that when an interference .DELTA.d of not smaller than 0.12% and not larger than 0.8% of the outer diameter of said pipes is provided between said male and female threads by fastening said joint, opposite flanks of said male thread simultaneously come into contact with corresponding flanks of said female thread, and a gap is formed between a crest and a root of the respective male and female threads,and wherein said load flank angle .theta.1, a stabbing flank angle .theta.2 of said trapezoidal thread and dimensional tolerances of thread width and thread height of said trapezoidal thread satisfy the following condition (1) or (2) in order to make said gap not large than 0.2 mm:10.degree..ltoreq..THETA.1+.THETA.2>20.degree., (1)tolerance of thread width (Wt)=.+-.0.015 mm, andtolerance of thread height (Ht)=.+-.0.015 mm;20.degree..ltoreq..THETA.1+.THETA.2, (2)tolerance of thread width (Wt)=.+-.0.025 mm, andtolerance of thread height (Ht)=.+-.0.025 mm.