Segmented Cutting Edge Geometry for Self-Boring Screw Drilling
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Solution Overview
Problem
Existing self-drilling and thread-forming screws lack optimal drilling behavior and security during both manual and automatic screw connections, with known designs not adequately addressing the need for improved hole creation and thread formation efficiency.
Innovation Solution
A screw design featuring angled cutting edges that taper more sharply at the tip, with a point angle between 40-50° in the first section and 60-80° in the second section, and secondary cutting edges to smooth the drill hole, ensuring better hole creation and thread formation, along with a real tip for secure application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cutting edges run in a straight line from the tip to the outer end, then the structure is simple, but the drilling behavior is poor and the screw may slip during application
Solution Approach 1:
The cutting edge is divided into two distinct sections: a first section with a smaller angle (40-50°) for initial hole creation, and a second section with a larger angle (60-80°) for expanding the hole. This segmentation allows each section to perform its specific function optimally, improving drilling behavior while maintaining a manageable geometric complexity
Solution Approach 2:
Different sections of the cutting edge are given different angular characteristics tailored to their specific functions. The first section has a more acute angle for efficient material removal and hole creation, while the second section has a larger angle for hole expansion. This local differentiation of geometric properties optimizes the drilling process at each stage
2Productivity
If the point angle is large, then the screw is stable during application, but the drilling efficiency is reduced
Solution Approach 1:
The cutting edge is segmented into two sections with different angles. The first section uses a smaller angle (40-50°) to optimize drilling efficiency and material removal rate, while the second section uses a larger angle (60-80°) to provide stability during application. This segmentation allows both conflicting requirements to be satisfied in different zones
Solution Approach 2:
The first section of the cutting edge performs the preliminary action of creating a small initial hole with high efficiency. Once this preliminary hole is established, the second section then expands it to the final size. This preliminary action approach allows the screw to maintain stability while achieving high drilling efficiency in the initial stage
3Productivity
If the cutting edges enclose a smaller angle, then the hole creation is faster, but the thread formation quality deteriorates
Solution Approach 1:
The cutting edge geometry is segmented into two sections with different angular characteristics. The first section uses a smaller angle (40-50°) optimized for fast hole creation, while the second section uses a larger angle (60-80°) that provides better support for quality thread formation. This segmentation decouples the conflicting requirements of speed and quality
Solution Approach 2:
Different angular properties are assigned to different local regions of the cutting edge. The first section has a more acute angle for rapid material removal, while the second section has a larger angle for precise thread formation. This local quality differentiation ensures both high productivity and manufacturing precision are achieved in their respective zones
Data Source
Figure 1~3
Figure 4~5
AI summary
The invention relates to a self-boring and thread-forming screw containing a bore head (4) on the front end of the screw shaft (1) with two cutting edges (11) that run transversely to the longitudinal axis of the screw. The cutting edges (11) extend from a screw tip (10). The cutting edges form a first angle with each other in a first section (11a) that extends from the screw tip. Said first section (11a) is adjoined by a section (11b) in which the cutting edges form a greater angle with each other than in the first region. When seen from the side, the cutting edges run along two sections that form an angle with each other.