1. Field of the Invention
The present invention relates to a screw, in particular to a screw having the feature of efficient screwing with less torque.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional screw 1 comprises a head 11, a shank 12 extending therefrom and a plurality of threads 13 spirally connected to the shank 12 along the shank axial line “α”; wherein the thread 13 is consisted of an upper flank 131 and an opposite bottom flank 132. A plurality of slots 133 are formed on the thread 13 which divided the thread 13 into thread segments 134 with the first end surface 135 and the second end surface 136. The first end surface 135 and second end surface 136 are parallel to the shank axial line “α”. While screwing the screw 1, the first end surface 135 cuts the object 10 to bring in the screw 1. The first end surface 135 is unable to cut the fibers of object 10 efficiently in rotation of the screw 1, which results in fibers entwined on the shank 12 and hence slows down the screwing speed.
Referring to FIG. 3, another conventional screw 2 comprises a head 21, a shank 22 extending therefrom, and a plurality of threads 23 spirally connected to the shank 22 along the shank axial line “α”; wherein a plurality of slots 231 are widely opened and formed on the threads 23 to define a first end surface 232, a second end surface 233 and a third end surface 234. As shown in FIG. 4, during the operation, the slots 231 have a large space to receive a great amount of fibers from the object 20 to increase the tightness of screw 2. Nevertheless, the first end surface 232 is not able to cut up the fiber of the object 20 directly, making wood fiber to quickly gather around said shank 12, which increases screwing friction, and the decreases screwing speed.