1. Field of the Invention
The present invention relates to a screw, especially a screw for screwing wooden workpiece.
2. Description of the Prior Arts
Multiple types of screws are designed according to various applications and functions. Taking a screw for screwing wooden workpiece for example, said screw has a circular rod, a tip, a tool connecting part, and a thread. The tip is formed on a tail end of the circular rod. The tool connecting part is formed on a head end of the circular rod. The thread helically extends from an outer surface of the tip to an outer surface of the circular rod.
A hand tool or electric tool is connected to the tool connecting part of the screw by a user, and the tip of the screw is disposed towards the wooden workpiece. The screw is applied with twisting force by the hand tool or the electric tool to make the tip and the thread of the screw bore a hole and tap in the workpiece to be securely screwed with workpiece.
Though the conventional screw is an element for securely fastening the workpiece, the chips produced from the boring and tapping processes are obstructed by thermal expansion caused by the friction acting between the workpiece and the screw.
In addition, an inclined angle of a thread wall towards the tip is greater than an inclined angle of the other thread wall, so the tapping process of the screw needs a large twisting force and is laborious for user.
To overcome the shortcomings, the present invention provides a screw to mitigate or obviate the aforementioned problems.
The main objective of the present invention is to provide a screw to eliminate obstruction of discharging chips of the conventional screw.
The screw in accordance with the present invention comprises a circular rod, a tip, a tool connecting part, a thread part, and multiple protruding ribs. The circular rod has a centerline, a tail end, and a head end. The tip is formed on the tail end of the circular rod. The tool connecting part is formed on the head end of the circular rod. The thread part helically extends from an outer surface of the tip to an outer surface of the circular rod. The multiple protruding ribs are formed on an outer surface around the tail end of the circular rod and are disposed in multiple thread pitches of the thread part from the tip. The multiple protruding ribs straightly extend on the circular rod and are parallel to the centerline of the circular rod, and a rib depth of each protruding rib is smaller than a thread depth of the thread part.
The conventional screw is applied with twisting force by the hand tool or the electric tool to make the tip and the thread of the screw bore a hole and tap in the workpiece, and the chips produced from the boring and tapping processes of the screw are discharged from the thread part to make the conventional screw securely fastened with workpiece. The screw in accordance with the present invention has the multiple protruding ribs. The multiple protruding ribs provide a reaming effect to reduce resistance of discharging the chips after the tip of the screw is screwed into the workpiece. So the chips produced from the workpiece are smoothly discharged from the workpiece.
In addition, an inclined angle of a thread wall of the thread part towards the tip is smaller than an inclined angle of the other thread wall of the thread, so twisting force applied to the tapping process of the screw is reduced and screwing of the screw is laborsaving for users.
Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
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Furthermore, when the screw is screwed into the workpieces 20, 30, an inclined angle of the first thread wall 131 of the thread part 13 towards the tip 11 is smaller than an inclined angle of the second thread wall 132 of the thread 13, thereby reducing twisting force applied to the boring and tapping process of the screw to save labor for user.
Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and features of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.