size of the parallel pin threads means that they are less prone to damage during this operation the joint is then ready to be screwed together it is important that the parallel thread engages before the inclined threads at this stage the metal to metal seal is not in contact with any other part as wrenching proceeds the pin moves axially into the box and causes engagement of the inclined threads followed by engagement of the metal to metal seal after a few turns probably two or three the taper thread on the pin begins to interfere with that on the box after a small amount of further rotation probably less than one turn the strain energy required to keep the joint together under operational conditions has been applied and the internal pin and box shoulders normally 90 u00b0 come into contact further torque is applied to compressively preload the pin seal area to a pre determined degree another advantage of the arrangement illustrated is that with normal taper thread previously used of large size such as 20 inches in outside diameter accurate stabbing is required angular misalignment of the axis of less than 1 u00b0 may result in cross threading of the joint which would be difficult in field operation to identify by means of the arrangement described above the joint illustrated can tolerate as has been explained an angular misalignment of up to 4 u00b0 even though it is expected that such would only be experienced during operations in high winds etc again although it has previously been proposed by others to use a bigger taper thread this does we believe lead to severe problems with thread galling on large sizes the arrangement in accordance with.