Wood Screw Shaft Step Geometry to Reduce Cracking and Friction

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Solution Overview

Problem

Conventional screws, particularly wood screws, cause material cracking and generate high friction during insertion.

Innovation Solution

A screw design featuring a cylindrical shaft behind the tip with a thickening, a step at an angle to the longitudinal axis, and additional thickenings to reduce material cracking and friction by widening the bore.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional screws are used, then the screw can be inserted into the material, but the wood cracks and high friction is generated

Engineering Contradiction:
Improveease of insertionVSAvoidmaterial cracking
Core Design Contradiction:
Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The cylindrical shaft with thickening performs preliminary action by cutting through the material before the threaded portion engages. This pre-cutting creates a clean bore that prevents cracking during subsequent threading, directly addressing the harm to the workpiece while maintaining insertion capability

Inventive Principle:
Principle #10Preliminary action

2Ease of operation

If conventional screws are used, then the screw can be inserted into the material, but high friction is generated during insertion

Engineering Contradiction:
Improveease of insertionVSAvoidfriction force
Core Design Contradiction:
Ease of operationVSForce

Solution Approach 1:

The cylindrical shaft with thickening performs preliminary action by cutting through the material before the threaded portion engages. This pre-cutting creates a clean bore that reduces friction during subsequent threading, directly addressing the high friction problem while maintaining insertion capability

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The invention changes the geometric parameters of the screw by introducing a cylindrical shaft with thickening that has specific diameter and length relationships to the thread. This parameter change optimizes the cutting action and reduces friction by ensuring the shaft diameter is larger than the thread core diameter, creating proper clearance

Inventive Principle:
Principle #35Parameter changes

3Object-affected harmful factors

If a cylindrical shaft with thickening is added to reduce cracking and friction, then material damage is reduced, but the screw structure becomes more complex

Engineering Contradiction:
Improvematerial crackingVSAvoidscrew structure complexity
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The screw is segmented into distinct functional zones: a cylindrical shaft with thickening for cutting and reducing friction, and a threaded portion for engagement. This segmentation allows each part to perform its specific function optimally while keeping the overall structure relatively simple through clear functional division

Inventive Principle:
Principle #1Segmentation

Data Source

PatentEP4361460B1Screw
Publication Date: 2026.01.28 SPAX INT GMBH & CO KG
  • EP4361460B1 patent drawingFigure 1a
  • EP4361460B1 patent drawingFigure 1b~1c
  • EP4361460B1 patent drawingFigure 2a

AI summary

A screw is proposed, having a thread and a conical tip, wherein a cylindrical shaft is formed behind the tip, and a thickening is arranged behind the shaft.