To prevent poor connection caused by destruction of a screw hole in screwing works of a thin steel sheet.
A trumpet portion 3 provided between a parallel thread portion 4 and screwhead 2 of a screw 1 used for a steel sheet is formed that the diameter in a lower end is equal to the root diameter of the parallel thread portion and that the diameter in an upper end is smaller than the diameter of the screwhead. Thus, the thread with the same peak-to-peak diameter of the thread is formed from the parallel thread portion to the vicinity of the upper end of the trumpet portion. The thin steel sheet is always engaged with the thread portion of the screw without exceeding the starting position of the thread, and completion for tightening of the screw can be surely detected by increasing fastening torque so that a flat portion in the peripheral edge of the undersurface of the screwhead is kept in pressed contact with the thin steel sheet. Consequently, any possibility of destructing the screw hole by excessive rotation of the screw can be eliminated, and occurrence of poor connection is also prevented.
NAKAGAWA YASUSHI
MACHIDA MITSUHISA
OGATA MOTOO
| JPS5052460A | 1975-05-09 | |||
| JP2000266020A | 2000-09-26 | |||
| JPH0488511U | 1992-07-31 |