Triangular Hole-Enlarging Screw for Debris-Reducing Reaming
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Solution Overview
Problem
Existing hole expanding screws face issues with high resistance and poor debris removal, leading to jamming and cracking of workpieces due to excessive debris accumulation during screwing, especially when the hole expanding portion with a larger cutting area is inserted.
Innovation Solution
A screw design featuring a hole-enlarging portion with three inclined edges spaced 120 degrees apart, forming a triangular transverse section, which guides debris upward through guiding slopes and facilitates smooth reaming and chip stirring, reducing resistance and improving screw-in speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the hole expanding portion with a circular cross section is used, then the screw can be driven into the workpiece, but high resistance and poor debris removal occur leading to jamming and cracking
Solution Approach 1:
The hole-enlarging portion is segmented into three inclined edges spaced 120 degrees apart, forming a triangular cross-section instead of a solid circular section. This segmentation creates channels between the edges that facilitate debris removal while maintaining the hole-enlarging function, thereby reducing debris accumulation and jamming.
Solution Approach 2:
The inclined edges are designed with asymmetric angles relative to the screw axis, creating guiding slopes that direct debris upward and outward. This asymmetric geometry optimizes the flow path for chip removal while distributing stress uniformly, preventing workpiece cracking during screwing.
2Manufacturing precision
If the hole expanding portion with larger cutting area is used, then hole reaming capability is improved, but debris generation increases leading to blockage and jamming
Solution Approach 1:
By dividing the hole-enlarging portion into three inclined edges, the design maintains a large effective cutting area for quality reaming while creating open spaces between edges that serve as debris egress paths, preventing blockage despite increased debris generation from larger cutting area.
Solution Approach 2:
The design extracts material in a controlled manner through the three inclined edges, removing debris through the spaces between edges as it is generated, rather than allowing it to accumulate. This continuous extraction prevents blockage in the guiding path.
Data Source
AI summary
A screw includes a head and a shank extending from the head, and a hole-enlarging portion formed on the shank. The hole-enlarging portion features no thread and a substantially triangular transverse section. The hole-enlarging portion includes three inclined edges spaced from one another in the circumferential direction of the shank, and a guiding slope is formed between two adjacent inclined edges. The shank defines a longitudinal axis and is provided with a thread. Each inclined edge extends toward the head in an inclined direction relative to a horizontal axis perpendicular to the longitudinal axis. The inclined direction of each inclined edge is identical to a direction in which the thread extends toward the head.