Type DLT-T Releasable Reversing Overshot, a new type of fishing tool, has many advantages owned by various overshot, box tap and the like, Its distinguishing features are as follows: to unscrew and recover the stuck fish: To release the fish down hole if necessary, to circulate the washing fluid as one of the accessories for reversing tools, it is widely used in well servicing.

Structure and application

Is consisting of top sub, spring, bowl, retaining seat, slip, control key, seal ring, seal seat, guide and so on. The upper end of top sub is connected with other tools and drill tool: The lower end of top sub is connected with bowl equipped with spring in the interior,There are three control keys uniformly distributed in the inner wall of the upper end of bowl, the control keys are used to control the position of retaining seat, Three keys are inserted separately in three grooves in the tapered interior section of lower end in bowl where three keys are used to transmit torque, The tapered interior section produces a pinch force against the slip to effect the fishing operation. The reversed operation can be effected when three keys transfer the torque from bowl to slip.The inclined angle among three control keys play an important role in retaining of slip conforming with bowl to ensure that the tools can be released easily from fish.

The retaining seat is installed at the upper end of external bowl where three keys are placed, the retaining seat not only can slide axially but also rotate round axial line so as to move with slip which is installed in internal circular recess.