1. Field of the Invention
This invention relates to a self-drilling screw, particularly to one having a drilling section that is provided with a cutting edge with a point for cutting a hole in a workpiece, a discharging section, a guiding section formed above the discharging section to be adjacent to a thread section and used to enable the screw vertically combined with a workpiece, and two discharging grooves. When the screw is rotated to move in a workpiece, the cutting edge can drill a hole, with cut bits moving into the discharge section and exhausted out of the drilled hole through the discharging grooves. After the screw moves into the workpiece for a certain depth, the guiding section can guide the screw to move straight in the workpiece, so the screw can be screwed accurately in the workpiece.
2. Description of the Prior Art
Commonly, a conventional self-drilling screw, as disclosed in U.S. Pat. No. 6,142,719, includes a head (3; 6), a thread section (2; 5) formed below the head, and a drilling section (1; 4) formed under the thread section. The drilling section (1; 4) is further provided with a first part (11; 41), a second part (12; 42), a first cutting edge (15; 45) and a second cutting edge (16; 46). And, two discharging grooves (13; 14; 43; 44) extend over the entire drilling section (1; 4) for discharging cut bits.
A first embodiment of the self-drilling screw in U.S. Pat. No. 6,142,719, the first cutting edge (15) of the drilling section (1) is formed in the first part (11) and the second cutting edge (16) is extended over the first part (11) and the second part (12). An edge (15′) of the second part (12) of the drilling section (1) is located inwardly of the first cutting edge (15) of the first part (11), unable to cut an edge. The radii of the first cutting edge (15) and the second cutting edge (16) are smaller than a half of a pitch diameter (D2) of the thread section (2) and bigger than a half of a root diameter (D1) of the thread section (2).
A second embodiment of the self-drilling screw in U.S. Pat. No. 6,142,719, the first cutting edge (45) of the drilling section (1) is extended over the first part (41) and the second part (42). An edge (46′) of the second part (42) is offset outwardly with respect to the second cutting edge (46) in the first part (41). The radii of the first cutting edge (45) and the second cutting edge (46) are equal to a half of a pitch diameter (D4) of the thread section (5).
According to U.S. Pat. No. 6,142,719, the first cutting edge (15; 45) and the second cutting edge (16; 46) are employed to drill a hole in a workpiece, with drillings discharged through the discharging grooves. However, as the radius (R1) of the opposite side of the second cutting edge (16) is smaller than a half of the root diameter (D1) of the thread section (2), the screw is apt to decline while passing the workpiece owing to no supporting part, keeping the thread section (2; 5) unable to be vertically combined with workpiece.
The object of this invention is to offer a self-drilling screw able to be vertically screwed into a workpiece smoothly with precision.
The main characteristics of the invention are a head, a thread section, and a drilling section. The drilling section includes two opposite cutting edges with an end point for cutting a hole in a workpiece, a discharging section for exhausting bits cut by the drilling section, a guiding section formed above the discharging section to be adjacent to the thread section, and two discharging grooves. When the screw is rotated to move in a workpiece, the cutting edges can drill a hole, with cut bits moved into the discharge section and exhausted out of the drilled hole through the discharging grooves. After the screw moves into the workpiece for a certain depth, the guiding section can guide the screw to move straight in the workpiece, so the screw can be screwed accurately in the workpiece.
Further, the guiding section can further be provided with two cutting wings that are to break off as soon as touching a metal workpiece so as to enable the thread section screwed in the metal workpiece combined with a wood workpiece.
This invention is better understood by referring to the accompanying drawings, wherein:
As shown in
The head 2 can be formed in any shape to be available for diverse drivers, in accordance with practical requirement.
The thread section 3 is formed under the head 2, usually provided with complete threads 30 having a shape or a pitch as practically required. Of course, the threads can be formed incomplete if necessary.
The drilling section 4 is formed under the thread section 3, provided with a cutting edge 41 including a point 40 and utilized to drill a metal workpiece (A), a discharging section 42 formed above the cutting edge 41 for temporarily accumulating cut bits to be exhausted out, a guiding section 43 formed above the discharging section 42 to connect with the thread section 3 and used to correct the screw for vertically combining with a metal workpiece (A), and two discharging grooves 44 extended up through the drilling section 41 and the discharging section 42 to some threads 300 of the thread section 3, with the threads 300 formed incomplete.
Further, as shown in
In using, as shown in
As shown in
The head 2 can be formed in any shape to be available for diverse drivers, in accordance with practical requirement.
The thread section 3 is formed under the head 2, usually provided with complete threads 30 having a shape or a pitch as practically required. Of course, the threads can be formed incomplete if necessary.
The drilling section 4 is formed under the thread section 3, provided with two opposite cutting edges 41 with an end point 40 and utilized to drill a metal workpiece (A), a discharging section 42 formed above the cutting edge 41 for temporarily accumulating cut bits to be exhausted out, a guiding section 43′ formed above the discharging section 42 to connect with the thread section 3, and a discharging groove 44 extended up from the cutting edge 41 through the discharging section 42 to the guiding section 43′ for conveniently exhausting drillings to lower resistance of drilling. Formed at two corresponding sides of the guiding section 43′ are two cutting wings 45, which can cut a hole in a wood workpiece (B) and a slot in the metal workpiece (A) so as to enable the thread section 3 to swiftly pass through the wood workpiece (B) to combine with the metal workpiece (A).
The outside diameter (D4) of the cutting edge 41 and the guiding section 43 is smaller than the pitch diameter (D1) of the thread section 3 and bigger than the root diameter (D2) of the thread section 3. The outside diameter (D3) of the discharging section 42 of the drilling section 4 is smaller than or equal to the root diameter (D2) of the thread section 3. And, the outside diameter (D5) of the cutting wings 45 is bigger than the pitch diameter (D1) of the thread section 3.
As shown in
While the preferred embodiment of the invention has been described above, it will be recognized and understood that various modifications may be made therein and the appended claims are intended to cover all such modifications that may fall within the spirit and scope of the invention.