The utility model discloses a deep hole screw tap used for manual operation and relates to a screw tap for machining deep hole threads through manual operation. The main problems that in the process of machining the deep hole threads through manual operation, because the high requirement for the coaxiality between the starting section of a screw tap and a thread bottom hole is not met, in the tapping process, the evenness of the machining allowance of the thread hole can not be guaranteed, an inclined hole or a thread-cutting hole is generated, machining can not be even finished, production efficiency is low, and the production cost of an enterprise is increased are solved. A limiting structure is arranged at the starting end of the screw tap, and a groove is formed between the limiting structure and a cutting edge of the screw tap. The coaxiality between the starting section of the screw rap and the thread bottom hole of a workpiece to be machine is guided and restrained through the limiting structure, the evenness of the machining allowance of the thread hole is guaranteed, the requirement for the skill level of an operator is greatly lowered, the production efficiency is greatly improved, and the production cost of the enterprise is reduced.