Screw tap with low extrusion resistance

The invention provides a screw tap with low extrusion resistance. The screw tap comprises a rod part and a threaded section, the threaded section is provided with a plurality of edge teeth around the mandrel, the periphery of each edge tooth is provided with two first cutting edges and two second cutting edges, a first distance is formed between the two first cutting edges, a second distance is formed between the two second cutting edges, and the first distance is larger than the second distance, so that the peripheries of the edge teeth of the screw tap are arranged in unequal lengths; in this way, small extrusion resistance can be provided, and the screw tap is not prone to breakage in the machining process. 本发明提供一种低挤压阻力的丝锥，其包括一杆部及一螺纹段。螺纹段绕着心轴设有复数个棱齿，每一个棱齿的周缘具有两个第一切削缘以及两个第二切削缘，且两第一切削缘之间具有一第一距离，两第二切削缘之间具有一第二距离，第一距离大于第二距离，而使丝锥的棱齿周缘为不等长设置，如此能够提供较小的挤压阻力，让丝锥在加工时不易发生断裂。