The die collar, also known as skirted taper tap, is a special external fishing tool that engages with the dropped tubular objects such as drill pipes and oil tubing, by tapping on the external wall of the objects. It can be used in fishing cylindrical objects without inner bore or stuck inner bore.The die collar is a long cylindrical integral structure composed of a Sub, a Tap body with cutter threads in the cone shaped interior as shown in the fig I. The die collar is made of high strength alloy and is made with cutting grooves in the fishing threads.
