Prefabricating device of gate screw rod jacket for oil fields

The utility model relates to a prefabricating device of a gate screw rod jacket for oil fields. The prefabricating device comprises an inner sleeve and an outer sleeve which are in hollow structures and a joint connected between the inner sleeve and the outer sleeve, the diameter of the inner sleeve is smaller than that of the outer sleeve, the joint is composed of an upper joint and a lower joint integrated with the upper joint, a stop shoulder is positioned at the position where the upper joint and the lower joint are connected, the caliber of the upper joint is smaller than that of the lower joint, the outer sleeve is inserted in the lower joint and abuts against the stop shoulder, the inner sleeve is inserted in the upper joint and in sliding fit with the inner wall of the upper joint, and the axis of the inner sleeve and the central axis of the outer sleeve are in the same straight line. According to the prefabricating device, the design of the inner and outer sleeves is adopted, measurement of the lengt