Self-tapping Screw with Oblique Arced Cutting Slot
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Solution Overview
Problem
Conventional self-tapping screws have insufficient drilling performance due to a small cutting surface and are prone to fracture when used with harder materials, and they often produce burrs during machining, affecting their quality.
Innovation Solution
The self-tapping screw design features a larger cutting surface with an arced cutting slot and multiple evacuation slots that are tilted relative to the center axis, enhancing drilling and tapping capabilities while facilitating efficient chip evacuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the V-shaped slot is axially cut into the shank and is adjacent to the center axis with a relatively small cutting surface, then the structure is simple and easy to manufacture, but the drilling performance is insufficient
Solution Approach 1:
The cutting slot is configured to extend obliquely from the tip portion toward the head along a direction tilted relative to the center axis, rather than axially. This dimensional change in the slot's orientation creates a larger cutting surface area while maintaining structural simplicity, thereby improving drilling performance without significantly increasing manufacturing complexity.
2Area of stationary object
If the arced surface axially and upwardly extends from a position at approximately two thread ridges apart from the tip, then the cutting surface area is increased, but the acting portion adjoining the tip becomes thinner and weaker
Solution Approach 1:
The arced surface extends obliquely upward along a direction tilted relative to the center axis rather than purely axially. This angular configuration allows the cutting surface to extend further without uniformly thinning the acting portion, as the material distribution is optimized along the tilted path, maintaining tip strength while increasing cutting surface area.
Solution Approach 2:
The arced surface is positioned to intersect with the periphery of the shank and the threaded portion, creating a blade portion at the intersection. This local quality enhancement concentrates the cutting function at the periphery where it is most needed, while the tilted extension preserves material thickness and strength in the critical tip region.
3Area of stationary object
If the V-shaped slot is cut deeper into the shank, then the cutting surface area is increased, but the acting portion becomes thinner and more prone to fracture
Solution Approach 1:
Instead of extending the cutting slot deeper axially, the slot is configured to extend obliquely at an angle relative to the center axis. This angular orientation increases the effective cutting surface area projected onto the workpiece while maintaining greater material thickness along the axial direction, thereby improving reliability and resistance to fracture.
4Productivity
If the cutting surface is enlarged by deeper V-shaped slot machining, then drilling capability is improved, but burrs easily occur between the thread ridges and are uneasy to be removed
Solution Approach 1:
The cutting slot extends obliquely rather than axially, creating a tilted cutting surface that reduces the tendency for material to fold back and form burrs between thread ridges. The angular configuration allows chips to be evacuated more efficiently along the tilted path, minimizing burr formation and improving overall manufacturing precision.
Solution Approach 2:
The arced surface with its curved geometry provides a smoother cutting action compared to straight axial slots. The curvature helps guide the cutting process and reduces sudden material removal that causes burrs, thereby improving the quality of the screw while maintaining enhanced drilling capability.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A self-tapping screw has a cutting slot (12) and at least one evacuation slot (14, 16, 18). The cutting slot (12) is formed in an acting portion (10), and has a chip evacuation surface (121) being tilted relative the center axis (4) of the shank (1) and a arced cutting surface (122) connected with the chip evacuation surface (121) to form a V-shaped section, upwardly extending from the tip of the tapered cone (11), and having a blade portion (13) formed by a portion of the arced cutting surface (122) intersecting with the periphery of a shank (1) and a threaded portion (3). The at least one evacuation slot (14, 16, 18) facilitates evacuation of chips generated when the self-tapping screw is drilled into a work piece. Accordingly, the self-tapping screw enhances the drilling, tapping and chip-evacuating capability.