Countersunk Screw Head With Inward Milling Ribs for Clean Wood Holes
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Solution Overview
Problem
Existing screws with inclined milling-ribs for countersinking often cause material breakage and uneven countersunk holes due to outward pressing of material, which is not desirable for smooth and secure fastening, especially in wood.
Innovation Solution
A screw design featuring a tapered underside with inward-pressing milling-ribs and concave cavities that compress material inwardly during countersinking, preventing breakage and enhancing the solid connection between the screw and material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If outward-pressing milling-ribs are used for countersinking, then the screw can be driven into the material, but material breakage and uneven countersunk holes occur
Solution Approach 1:
The patent inverts the conventional outward-pressing milling-ribs design by implementing inward-pressing milling-ribs. The front side of each milling-rib is inclined such that the part near the rim of the screw-head is leading during screwing-in, causing milled material to be pressed inwards towards the shank rather than outwards. This inversion resolves the contradiction by preventing material breakage while maintaining countersinking capability.
2Productivity
If inclined milling-ribs are used for countersinking, then cutting action is provided, but material is pressed outwards causing fringes and breakage
Solution Approach 1:
The patent applies the inversion principle by reversing the pressing direction of the milling-ribs from outward to inward. The inclination angle and orientation of the front side of each milling-rib are specifically designed to direct milled material inwards towards the shank during countersinking, eliminating the harmful outward pressing effect that causes fringes and breakage while preserving the beneficial cutting action.
3Ease of operation
If milling-ribs are provided on the tapered surface, then countersinking is enabled, but material compression is insufficient for strong connection
Solution Approach 1:
The patent applies the local quality principle by creating cavities between the milling-ribs on the tapered underside of the screw-head. These cavities are specifically positioned to receive and compress milled material inwardly towards the shank. The local compression zones formed by the cavities enhance the connection strength between the screw and the workpiece, resolving the contradiction between enabling countersinking and achieving strong connection.
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 screw achieves efficient and aggressive cutting of wood fibers, minimizing fringes and ensuring proper stopping without material breakage, providing a strong and compact connection with high tightening force.
Implementation Method 1
the milling-ribs are inclined for pressing milled material inwards towards the shank during countersinking of the screw
Implementation Method 2
efficient and aggressive cutting of wood fibers
Data Source
AI summary
In order to prevent wood fringes at the edge of a hole from a countersunk screw (1), the screw-head (2) is provided with a tapering underside and inclined milling-ribs with cavities between the milling-ribs on the tapering underside.