Abstract: A pipe nesting and denesting apparatus is efficiency in transportation of many pipes different in diameters, and said apparatus can operate in a short time nesting work without injuring pipes. Inside the rails of said apparatus, a receiving stand for receiving pipe which is movable up and down is provided, said pipe is moved by a supporting rod on a carriage, and pipes different in diameters are inserted or pulled up on an adjustable nesting stand.

Abstract: A grinding apparatus for reforming a surface of a commutator of a motor which has been worn or damaged, comprising a main spindle slidably movable in a guide sleeve as a housing of the apparatus, a cutting and feeding mechanism located at the back end of the main spindle for finely adjusting the grinding depth of a grinding stone arranged at the front end of the main spindle, and a clamping mechanism arranged on the guide sleeve for mounting the apparatus by forced engagement of the clamping mechanism in an opening of a casing of the motor for changing carbon brushes.