Abstract: A screw includes a head having a top face and a conical bottom surface, a shank, and thread convolutions. A chip guiding channel is recessedly formed on the conical bottom surface. On the conical bottom surface are spirally disposed a cutting portion which has a plurality cutting units sequentially arranged in a spiral manner, thereby allowing the chip guiding channel to be surrounded by the cutting units along a spiral track. The spiral arrangement of the cutting units assists the head in cutting fibers of a workpiece which are wound around the head into small chips in a continuous and spiral severing manner to reduce drilling torque and resistance, and the spirally-defined chip guiding channel also facilitates a smooth removal of the chips, thereby allowing the head to fit level with a top surface of the workpiece and increasing a fastening effect.

Abstract: A screw includes a head having a top face and a conical bottom surface, a shank, and thread convolutions. A chip guiding channel is recessedly formed on the conical bottom surface. On the conical bottom surface are spirally disposed a cutting portion which has a plurality cutting units sequentially arranged in a spiral manner, thereby allowing the chip guiding channel to be surrounded by the cutting units along a spiral track. The spiral arrangement of the cutting units assists the head in cutting fibers of a workpiece which are wound around the head into small chips in a continuous and spiral severing manner to reduce drilling torque and resistance, and the spirally-defined chip guiding channel also facilitates a smooth removal of the chips, thereby allowing the head to fit level with a top surface of the workpiece and increasing a fastening effect.

Abstract: A screw with multiple thread angles includes a shank, a main threaded portion having thread convolutions, and a head. Each thread convolution defines different thread angles from a root to a thread crest in sequence, namely a first thread angle ranging between 70 degrees and 75 degrees, a second thread angle ranging between 37 degrees and 43 degrees, and a third thread angle ranging between 20 degrees and 23 degrees. Notches are recessed into the thread crest for attaining a smooth removal of cut chips. The third thread angle assists each thread convolution in cutting a workpiece sharply to facilitate a quick cutting operation. The second thread angle and the first thread angle help widen a cutting track caused by the cutting operation gradually so that the thread convolutions are continuously drilled into the workpiece by a multi-stage reaming and drilling operation to achieve a quick screwing effect.

Abstract: A welding mechanism for welding different blank sections includes a welding device and a carrier. The carrier has a base, two opposite positioning members, an operating set disposed between the positioning members and driven by a power source, and a holding member and a pushing member which are respectively disposed relative to the positioning members. The blank sections, including a front section and a rear section, are separately placed on the operating set. The front section is restricted by the holding member. The pushing member pushes the rear section, so the two sections meet at a joint. When the two sections rotate synchronously along with the rotation of the operating set, the welding device welds the two sections at the joint circumferentially to produce a bi-compositional screw, thereby preventing the generation of air and pores inside the joint after welding, increasing processing quality, and reducing processing costs.

Abstract: A screw capable of reducing drilling torque includes a shank provided with cutting threads, and a head and a drilling portion respectively formed at two ends of the shank. Each cutting thread has two opposite flank surfaces converging at a thread crest. On the thread crest are recessedly formed notches alternating with grooves. Each groove has an upper crest edge and a lower crest edge meeting the flank surfaces respectively. Each notch has a first cutting edge and a second cutting edge meeting the flank surfaces respectively. The above cutting edges and crest edges cooperate to provide multiple cutting points, thereby increasing the cutting efficiency, preventing the improper entanglement of fibers, and reducing drilling torque for easier screwing. The notches and grooves accommodate and press partial debris for achieving a stable and tight engagement between the screw and an object and increasing the ability of resisting the pulling-out force.

Abstract: A welding mechanism for welding different blank sections includes a welding device and a carrier. The carrier has a base, two opposite positioning members, an operating set disposed between the positioning members and driven by a power source, and a holding member and a pushing member which are respectively disposed relative to the positioning members. The blank sections, including a front section and a rear section, are separately placed on the operating set. The front section is restricted by the holding member. The pushing member pushes the rear section, so the two sections meet at a joint. When the two sections rotate synchronously along with the rotation of the operating set, the welding device welds the two sections at the joint circumferentially to produce a bi-compositional screw, thereby preventing the generation of air and pores inside the joint after welding, increasing processing quality, and reducing processing costs.

Abstract: A welding method for manufacturing a bi-compositional screw includes a preparing operation, a welding operation and a forming operation. The preparing operation prepares two raw blanks made of different materials and respectively processed to provide a front section and a rear section. The welding operation places the two sections on a positioning device to allow the two sections to meet closely at a joint along an axis, and then applies a welding device to weld the two sections at the joint in a circumferential direction when the two sections are rotated in the same rotational direction, thereby attaining a bi-compositional blank without causing waste extruded out of the joint. The forming operation forms a plurality of threads on the bi-compositional blank to forma bi-compositional screw. The method prevents the generation of air and pores inside the joint after welding, reduces processing costs, and ensures preferable processing quality.

Abstract: A screw capable of reducing drilling torque includes a shank provided with cutting threads, and a head and a drilling portion respectively formed at two ends of the shank. Each cutting thread has two opposite flank surfaces converging at a thread crest. On the thread crest are recessedly formed notches alternating with grooves. Each groove has an upper crest edge and a lower crest edge meeting the flank surfaces respectively. Each notch has a first cutting edge and a second cutting edge meeting the flank surfaces respectively. The above cutting edges and crest edges cooperate to provide multiple cutting points, thereby increasing the cutting efficiency, preventing the improper entanglement of fibers, and reducing drilling torque for easier screwing. The notches and grooves accommodate and press partial debris for achieving a stable and tight engagement between the screw and an object and increasing the ability of resisting the pulling-out force.