Fret Contouring File With Depth Stop for Height Preservation

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Solution Overview

Problem

The process of restoring the rounded outer contours of frets on a fingerboard while maintaining their height is complex and time-consuming, as it requires precise leveling to prevent unwanted buzzing and preserve pitch accuracy.

Innovation Solution

A file with an abrasive machining surface and a non-abrasive depth stop element is used to machine the frets, ensuring that the fret height is maintained during the leveling process, allowing for the creation of an uneven contour with transverse curvature.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a file with only abrasive surfaces is used to level frets, then the contour can be machined, but the fret height cannot be maintained and unwanted material removal occurs

Engineering Contradiction:
Improvecontour machiningVSAvoidfret height maintenance
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

The file is divided into distinct functional segments: abrasive file elements for contour machining and non-abrasive depth stop elements for height maintenance. This segmentation allows each part to perform its specific function without interfering with the other, resolving the contradiction between machining capability and precision maintenance.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Different regions of the file have different properties: the file elements have abrasive surfaces for material removal, while the depth stop elements have smooth non-abrasive surfaces for precise height control. This local differentiation enables the single tool to both machine contours and maintain heights simultaneously.

Inventive Principle:
Principle #3Local quality

2Productivity

If the leveling process is made simple and fast, then productivity increases, but the precision of fret height and pitch accuracy deteriorates

Engineering Contradiction:
Improveleveling speedVSAvoidfret height precision
Core Design Contradiction:
ProductivityVSManufacturing precision

Solution Approach 1:

The depth stop elements are pre-configured with specific heights corresponding to the desired fret levels. This preliminary setup allows the operator to quickly level multiple frets without repeated measurements, achieving both high productivity and consistent precision through pre-planned tool configuration.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The file design enables self-controlled precision: the depth stop elements automatically prevent over-cutting by contacting the fret surface at the correct height, providing inherent precision control without requiring constant operator intervention or complex measurement procedures during the leveling process.

Inventive Principle:
Principle #25Self-service

3Device complexity

If a single file element is used for both depth control and contour machining, then device complexity is reduced, but the file quickly wears out and loses precision

Engineering Contradiction:
Improvefile structureVSAvoidfile durability
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The file consists of separate file elements and depth stop elements that can be independently replaced. When the abrasive file elements wear out, only they need to be replaced while the precision-critical depth stop elements remain intact, significantly extending the overall tool life and maintaining reliability.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The design allows the consumable file elements to be discarded when worn, while the non-consumable depth stop elements are recovered and reused. This selective replacement strategy maintains precision while managing the costs and complexity of tool maintenance.

Inventive Principle:
Principle #34Discarding and recovering

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 file simplifies the production of a workpiece with a transverse curvature by preventing unintended material removal, maintaining fret height, and ensuring precise contour restoration, thus enhancing the playing quality of stringed instruments.

Implementation Method 1

at least one file element (5, 6) with an abrasive machining surface (8)

Methodology Applied
Scientific EffectAbrasion: Abrasion

Implementation Method 2

depth stop element (7) with a non-abrasive sliding surface (9)

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP4706858A2File for generating an uneven contour, in particular with a transverse curvature
Publication Date: 2026.03.11 ERTL LOTHAR
  • EP4706858A2 patent drawingFigure 1
  • EP4706858A2 patent drawingFigure 2
  • EP4706858A2 patent drawingFigure 3~5

AI summary

A file (1) for producing an uneven contour, in particular with a transverse curvature on a workpiece (11), comprises a longitudinal axis (3), at least one file element (5, 6) with an abrasive machining surface (8) and a depth stop element (7) with a non-abrasive sliding surface (9), wherein the at least one file element (5, 6) and the depth stop element (7) are arranged next to each other in a plane oriented perpendicular to the longitudinal axis (3).