Abstract: The present invention provides a screw, comprising a screw head having a drive recess and a screw shank having threads and being integrally formed with the screw head, wherein the drive recess includes a plurality of engaging grooves equiangularly radiating from an axis of the screw in plan view, a bottom face of each engaging groove having a steep slope, which is near to the screw shank, and a gentle slope, which is far from the screw shank, for enlarging the engaging area of the engaging grooves.

Abstract: The present invention provides a screw, comprising a screw head having a drive recess and a screw shank having threads and being integrally formed with the screw head, wherein the drive recess includes a plurality of engaging grooves equiangularly radiating from an axis of the screw in plan view, a bottom face of each engaging groove having a steep slope, which is near to the screw shank, and a gentle slope, which is far from the screw shank, for enlarging the engaging area of the engaging grooves.

Abstract: A screw with a thin head comprising a screw head (2) and a shank (4), and with its top (5) forming a circular arc of a large radius has an unthreaded part (20) tapered down between the bearing surface (6) and the thread (3) and has a radius (21) connected to the thread portion (3), and therefore it will be readily produced to be used for compact products and correspond with thin products. And the radius (21) is connected to the unthreaded part (20) of the shank on one hand and to the screw ridge (3) on the other, preventing stress concentration at this part from occurring at time of fastening and a long time after the fastening of the screw, so ensuring a fastening strength, without causing a fatigue fracture. And further, when heating and plating treatments have been given to the screw, as the top of the screw head is not flat, there is no possibility of the heads of the screws being stacked to each other in the course of mass production, ensuring stable heat and plating treatments.

Abstract: A screw with a thin head comprising a screw head (2) and a shank (4), and with its top (5) forming a circular arc of a large radius has an unthreaded part (20) tapered down between the bearing surface (6) and the thread (3) and has a radius (21) connected to the thread portion (3), and therefore it will be readily produced to be used for compact products and correspond with thin products. And the radius (21) is connected to the unthreaded part (20) of the shank on one hand and to the screw ridge (3) on the other, preventing stress concentration at this part from occurring at time of fastening and a long time after the fastening of the screw, so ensuring a fastening strength, without causing a fatigue fracture. And further, when heating and plating treatments have been given to the screw, as the top of the screw head is not flat, there is no possibility of the heads of the screws being stacked to each other in the course of mass production, ensuring stable heat and plating treatments.