Tapered Screw Head With Inward Milling Ribs for Clean Countersinking

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Solution Overview

Problem

Existing screws with inclined milling-ribs either press material outward or have inefficient cutting mechanisms, leading to incomplete countersinking and broken wood fibers during screwing into wood, which affects the screw's holding strength and appearance.

Innovation Solution

A screw with a tapered screw-head featuring inward-pressing milling-ribs having a planar front-side with a sharp, smoothly convex milling-edge, oriented to efficiently cut and compact wood fibers inwardly, preventing further milling and ensuring secure screwing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If outwards-pressing milling-ribs are used, then the screw can be driven into the material, but the material is pressed outwards causing broken wood fibers and incomplete countersinking

Engineering Contradiction:

Improvecountersinking qualityVSAvoidbroken wood fibers

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent inverts the conventional outwards-pressing milling-ribs design by implementing inwards-pressing milling-ribs. The front-side of each milling-rib is inclined such that during clockwise rotation, the milling-edges press the wood fibers inwards towards the shank rather than outwards, fundamentally reversing the material flow direction to achieve clean countersinking without fiber breakage

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the inclination angle parameter of the milling-rib front-sides to achieve the inwards-pressing effect. Specifically, the front-side is inclined by an angle in the direction of the screwing-in direction relative to a cross-sectional plane containing the central axis, optimizing the material compression and flow characteristics for clean countersinking

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If conventional milling-ribs are used, then the screw structure is simple, but the cutting mechanism is inefficient leading to fringes and poor appearance

Engineering Contradiction:

Improvescrew structureVSAvoidcountersinking cleanliness

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by providing different surface characteristics at different locations on the screw-head. The tapered surface features milling-ribs with specific front-side inclinations and sharp milling-edges at the periphery, while the central area allows fiber compaction. This localized functional differentiation achieves efficient cutting and clean countersinking without requiring complex overall screw restructuring

Inventive Principle:

Principle #3Local quality

3Reliability

If inwards-pressing milling-ribs are implemented, then material is compacted efficiently, but the screw-head design becomes more complex

Engineering Contradiction:

Improveholding strengthVSAvoidscrew-head design

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The tapered surface with inwards-pressing milling-ribs serves multiple functions simultaneously: it acts as a cutting surface with sharp milling-edges for efficient material removal, a compaction surface for densifying wood fibers towards the shank, and a stopping surface that prevents over-screwing. This multi-functionality achieves reliable holding strength while maintaining a relatively simple integrated screw-head design

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 inward-pressing milling-ribs provide aggressive cutting and efficient material compaction, resulting in a clean countersunk hole with minimized fringes and enhanced holding strength, allowing for proper screw stopping and high tightening force.

Implementation Method 1

The front-side is inclined relatively to the taper-direction, wherein the inclination of the front-side and the milling-edge are oriented for inward-pressing of the material towards the shank during countersinking of the screw-head in the material

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentEP3704390B1Screw with tapered screw-head, use of a screw and a method for countersinking the screw

Publication Date: 2023.12.06 DISSING

Figure 1a~1d
Figure 1e~1f
Figure 2a~2b

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 (8) on the tapering underside. Each milling-rib (8) has a planar front-side (15) delimited by smoothly curved convex milling-edge (17) for milling the material during countersinking of the screw-head (2).