Asymmetric Drill Cutting Edge Geometry for Flank Face Chipping

Solution Overview

Problem

Existing drills suffer from insufficient strength at the cutting edge under high load conditions and are prone to chipping on the flank face during high-feed cutting operations.

Innovation Solution

The drill design incorporates a main cutting edge with a first curved portion having a larger curvature radius than a second curved portion, and optionally includes a connecting portion, to enhance strength and reduce chipping on the flank face.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the main cutting edge has a small curvature radius, then the cutting edge strength is improved, but chipping occurs on the flank face under high feed conditions

Engineering Contradiction:

Improvecutting edge strengthVSAvoidflank face integrity

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies different curvature radii to different portions of the main cutting edge. The first curved portion (contiguous with the flank face) has a larger curvature radius to prevent chipping, while the second curved portion (contiguous with the rake face) has a smaller curvature radius to maintain cutting edge strength. This local differentiation resolves the contradiction between preventing flank face chipping and maintaining cutting edge strength.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces asymmetric curvature radii in the main cutting edge design. Instead of using a uniform curvature radius, the first curvature radius (R1) is made larger than the second curvature radius (R2). This asymmetric design allows the cutting edge to have different geometric characteristics at different locations, enabling it to simultaneously resist chipping on the flank face and maintain sufficient strength at the cutting edge.

Inventive Principle:

Principle #4Asymmetry

2Reliability

If the main cutting edge has a large curvature radius, then chipping on the flank face is suppressed, but the cutting edge strength becomes insufficient under high load conditions

Engineering Contradiction:

Improveflank face integrityVSAvoidcutting edge strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies different curvature radii to different portions of the main cutting edge. The first curved portion (contiguous with the flank face) has a larger curvature radius to prevent chipping, while the second curved portion (contiguous with the rake face) has a smaller curvature radius to maintain cutting edge strength. This local differentiation resolves the contradiction between preventing flank face chipping and maintaining cutting edge strength.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The main cutting edge is segmented into two distinct curved portions: the first curved portion contiguous with the flank face and the second curved portion contiguous with the rake face. Each segment is assigned a different curvature radius optimized for its specific function. This segmentation allows the cutting edge to simultaneously achieve chip prevention (via larger R1) and strength (via smaller R2) without compromise.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12605773B2Drill and cutting method

Publication Date: 2026.04.21 SUMITOMO ELECTRIC HARDMETAL CORP

AI summary

A drill includes a flank face, a rake face, and a main cutting edge on a ridgeline between the rake face and the flank face. The main cutting edge has a first curved portion having a curved shape contiguous with the flank face and a second curved portion having a curved shape contiguous with the rake face in a sectional view orthogonal to an extending direction of the main cutting edge. A first curvature radius of the first curved portion is larger than a second curvature radius of the second curved portion.