This type of mechanical external cutter is a mechanical cutting tool that cuts from the outside  of casing,tubing,drill pipe,etc.It  can  cut  from  outside  of pipe  and  take  out  the  cutting section,it uses spring automatic running,and avoid accident by driller’s negligence which  cause  excessive  pulling  force  and  destroy  cutter.It  is  normally  connected  with washover pipe,so as to cut and take out the pipe at proper position,it needs to change different cutter for different spec.pipes and change the corresponding clamping sleeve