Segmented Drill Point Geometry for Self-Centering on Uneven Surfaces

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Solution Overview

Problem

Conventional drilling tools experience deflection and breakage when used on non-flat or non-perpendicular surfaces due to lack of self-centering, especially when used on lathes with rotating workpieces, leading to significant lateral forces and concentricity errors.

Innovation Solution

A drilling tool design featuring two main cutting edges with distinct point angles, where the first section has a point angle greater than or equal to 180° and the second section less than 180°, creating a cutting tip at a distance from the central axis, allowing for pre-center positioning and improved self-centering, which reduces the risk of breakage and enhances feed rates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a transverse cutting edge is provided centrally to ensure self-centering, then good self-centering is achieved on flat surfaces, but the drill bit deflects laterally and may break on non-flat or non-perpendicular surfaces

Engineering Contradiction:

Improveself-centering accuracyVSAvoidrisk of breakage

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The main cutting edges are divided into multiple sections along their length, with each section having different point angles. The first section has a point angle ≥180° while the second section has a point angle <180°. This segmentation allows different portions of the cutting edge to engage the workpiece at different stages, improving self-centering while reducing lateral forces that cause deflection and breakage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the main cutting edges are given different local properties through varying point angles. The first section with point angle ≥180° provides initial engagement and self-centering, while the second section with point angle <180° provides stable cutting. This local differentiation resolves the contradiction between self-centering accuracy and reliability.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If the cutting edges are positioned on the central axis, then self-centering is improved, but lateral forces increase causing deflection and breakage on non-perpendicular surfaces

Engineering Contradiction:

Improvecentering accuracyVSAvoidlateral force

Core Design Contradiction:

Manufacturing precisionVSForce

Solution Approach 1:

The cutting edges are segmented into sections with different point angles, allowing the force distribution to be optimized. The first section with point angle ≥180° engages first to establish centering, while the second section with point angle <180° engages subsequently to provide stable cutting with reduced lateral forces.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The point angle parameter is changed along the length of the cutting edges, with the first section having point angle ≥180° and the second section having point angle <180°. This parameter variation allows the cutting edge to adapt to different engagement stages, reducing lateral forces while maintaining centering accuracy.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If conventional drilling tools are used on lathes with rotating workpieces, then machining can be performed, but significant lateral forces cause deflection and concentricity errors

Engineering Contradiction:

Improvemachining capabilityVSAvoidconcentricity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The segmented main cutting edges with different point angles in different sections enable the drill bit to handle the unique challenges of lathe machining. The first section with point angle ≥180° provides initial engagement and self-centering on the rotating workpiece, while the second section with point angle <180° provides stable cutting with reduced lateral forces, improving concentricity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the cutting edges have different local properties (point angles) optimized for specific functions. The first section's point angle ≥180° is optimized for initial engagement and self-centering, while the second section's point angle <180° is optimized for stable cutting with reduced lateral forces, resolving the contradiction between productivity and concentricity.

Inventive Principle:

Principle #3Local quality

Data Source

PatentEP3414038B1Drilling tool

Publication Date: 2022.11.16 MAPAL DR KRESS SE & CO KG

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AI summary

The invention relates to a drilling tool (1) having - at least two main lips (11) which are provided on the end side (5) and which - each have a plurality of sections (15, 17), of which - a first section (15) of the at least two main lips (11) is arranged closer to the central axis (13) and a second section (17) adjoins that end of the first section (15) that is remote from the central axis, wherein - the first sections (15) of the at least two main lips (11) enclose a point angle si > 180° with one another and the second sections (17) enclose a point angle Sa ≤ 180° with one another, with the result that - in the transition region between the first section (15) and the second section (17), a point (21) arranged at a distance from the central axis (13) is formed, and wherein the lips of the at least two main lips (11) exhibit a below-centre position in the first section (15), and wherein the lips of the at least two main lips (11) exhibit an ahead-of-centre position in the second section (17).