Patent ID: 6877202

Claim:
A method of manufacturing a threaded joint for a pipe having a pin portion with a male thread comprising a tapered thread with a thread cross-sectional shape which is roughly trapezoidal, and a box portion having a female thread which engages with the male thread and which comprises a tapered thread with a thread cross-sectional shape which is roughly trapezoidal, a metal seal portion provided on the pin portion and the box portion, a torque shoulder portion provided on the end of the pin portion and on a portion of the box portion which abuts therewith, characterized by determining the dimensions of each portion by: determining the outer diameter (OD) and the pipe wall thickness (t) of a pipe having the pin portion, determining the lip inner diameter (D 2 ) of the pin portion based on the determined pipe outer diameter (OD) and pipe wall thickness (t), and determining the inner diameter (D 1 ) of the box portion based on the determined lip inner diameter (D 2 ) of the pin portion, provisionally determining a lip thickness ratio (X) based on the determined pipe outer diameter (OD) and pipe wall thickness (t), provisionally determining the lip thickness (lt) of the pin portion and the lip root outer diameter (DB) of the pin portion based on the provisionally determined lip thickness ratio (X), and determining the thread engagement height (h) and the thread pitch (P) based on the determined pipe outer diameter (OD) and pipe wall thickness (t), provisionally determining the thread taper (Tt) based on the determined pipe outer diameter (OD) and pipe wall thickness (t), and on the provisionally determined lip outer diameter (DB) of the pin portion, the provisionally determined complete engagement thread length (L) and the determined thread engagement height (h), determining the lip length (l), the seal length of the pin portion (S P ), the seal taper (Ts), the shoulder angle (θ 1 ), and the lip thickness ratio (X) based on the provisionally determined lip thickness (lt) of the pin portion and the provisionally determined lip root outer diameter (DB) of the pin portion so that a function f is greater than 1.2, and thereby determining the shape of the pin lip, and determining the lip thickness (lt) of the pin portion and the lip outer diameter (DB) of the pin portion, and also determining the diameter of the end of the lip portion (Papex), determining the thread taper (Tt) and the complete engagement thread length (L) based on the determined lip thickness (lt) of the pin portion, the determined lip root outer diameter (DB) and the determined thread engagement height (h) of the pin portion, and determining the thread parallel portion diameter (DA) of the box portion, and determining the load flank angle (α), the stabbing flank angle (β), the gap (δ) between the stabbing flanks, and the gap (γ) between the thread crests, and determining the shape of the seal portion including the seal length (S B ) of the box portion based on the seal length (S P ) of the pin portion and the dimensions of each portion of the pin portion.