Self-Drilling Screw Tip Geometry for Fast Cutting and Chip Removal
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Solution Overview
Problem
Conventional self-drilling screws face issues with cutting performance and screwing resistance due to the included angle of the tip, leading to inefficient screwing, potential workpiece damage, and chip accumulation, which increases friction and the risk of cracking.
Innovation Solution
A self-drilling screw design featuring a leading section with a drilling portion having a first included angle of not more than 60 degrees, two blade portions with a second included angle of not more than 50 degrees, and concave surfaces and discharge grooves to facilitate accurate positioning, sharp cutting, and efficient chip removal, reducing screwing resistance and preventing workpiece cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the included angle of the tip is reduced to make it sharper, then the sharpness and positioning accuracy improve, but the cutting edge area decreases reducing cutting effectiveness
Solution Approach 1:
The leading section is divided into two functional parts: a drilling portion with a small included angle (≤60°) for sharp positioning, and blade portions with larger included angles (≤50°) for effective cutting. This segmentation allows each part to optimize its geometry for its specific function without compromising the other.
Solution Approach 2:
Different regions of the leading section have different geometric properties tailored to their local functions. The drilling portion has a smaller included angle for penetration and positioning, while the blade portions have larger included angles for material removal, creating local optimization of geometry throughout the structure.
2Productivity
If the included angle of the tip is increased to enlarge the cutting edge area, then the cutting effectiveness improves, but the sharpness and positioning accuracy deteriorate
Solution Approach 1:
The cutting function is separated from the positioning function. The drilling portion with small included angle handles positioning, while the blade portions with larger included angles handle cutting, eliminating the need to compromise between these conflicting requirements.
Solution Approach 2:
The solution moves from a single-angle geometry to a multi-angle geometry along the length of the leading section. By varying the included angle along the axial dimension, the patent achieves both sharp positioning capability and effective cutting capability that cannot be obtained with a uniform angle.
3Productivity
If chips are not efficiently removed from the cutting zone, then screwing resistance increases and workpiece cracking occurs, but adding larger discharge grooves may weaken the structural integrity
Solution Approach 1:
The discharge grooves have curved cross-sections that facilitate chip flow. The curved geometry of the grooves helps guide chips smoothly from the cutting zone to the exterior, improving chip removal efficiency through optimized flow paths rather than simply increasing groove size.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design enables accurate, quick, and firm screwing with reduced resistance and prevents workpiece cracking by ensuring efficient chip removal and minimizing friction, allowing for smooth operation.
Implementation Method 1
Two cutting edges 135 each are formed at a place where the flute 133 and the bevel surface 132 meet. In operation, a force is added to rotate the head 11 after the tip 134 is put on a surface of a workpiece. The cutting edges 135 serve to cut the workpiece
Implementation Method 2
two opposite flutes 133 formed on the drilling body 131. chips caused by the cutting action travel along the flute 133 for being removed from the workpiece
Implementation Method 3
a shank 12 connected to the head 11 and provided with threads spirally formed thereon. The shank 12 with thread convolutions are gradually screwed into the workpiece during the cutting action
Data Source
AI summary
A self-drilling screw includes a leading section having a drill body and opposite discharge grooves formed on the drill body. The drill body and the discharge grooves meet at cutting edges. On the drill body are formed two blade portions connected to the cutting edges and tapering at respective second tips. The blade portion has a second included angle of not more than 50 degrees. Between the blade portions is formed a drilling portion terminating at a first tip and having a first included angle of not more than 60 degrees. Two opposite concave surfaces each extend from the drilling portion to each blade portion. The first tip and the second tips are situated at different places. Accordingly, the end of the leading section presents a shape of a curved bow riser to cut quickly and help quick removal of chips, thereby decreasing resistance and preventing the cracking problem.