1. Accordingly, when the screw is fastened to a low-height female threaded portion of a target object, the fastening action is facilitated and the defect rate is reduced to a minimum, and this provides improved productivity, lower costs and increased joint force.

따라서 상대물의 깊이가 얕은 암나사부에 체결될 때 체결이 매우 용이하게 되고 불량률이 최소화되며, 이에 따라 생산성이 향상되고 코스트가 절감되며 체결력이 증대된다.