The object of the invention is to provide a fuel injection nozzle with which occurrence of cavitation erosion due to occurrence of separation of fuel flow near the needle valve and injection holes is suppressed and variation in fuel injection characteristic is reduced, a method of machining injection holes, and an apparatus therefore to attain the object. The lower jaw is configured to receive a removable cartridge when in an open position. Also, a method of using a tool belt that includes a pouch portion and a magnet.