The ND-J type internal cutter is a down-hole cutting tool designed to cut casings, tubings and drill pipes mechanically. It owns some advantages of simple structure, reliable performance, high cutting efficiency. In order not to cut casings, tubing couplings, before run in hole, the cutter shall be kept away from collar position, if condition is allowed, it can be used with collar finder. It can be used with releasing spear, the cut off pipe strings can be either pulled out of hole with cutter or canght out by fishing tools alone.