Quadrangular Drill Insert Curved Edges Centering

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Solution Overview

Problem

Conventional quadrangular indexable drill inserts with rectangular cutting edges tend to drift from the center due to uneven cutting forces, leading to poor surface finish and narrow wall issues, and often rub against the drilling hole surface when the diameter is less than a predetermined value.

Innovation Solution

A quadrangular indexable drill insert with four cutting edges divided into part edges, featuring a combination of convex and concave curves, and curved nose portions to direct forces to the center, along with a through hole and chamfer for secure mounting and reduced wear, preventing drifting and improving chip formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If rectangular cutting edges are used in conventional drill inserts, then the manufacturing and assembly process is simple, but the drill tends to drift away from its center due to uneven cutting forces

Engineering Contradiction:

Improvesimplicity of cutting edge designVSAvoiddrill centering accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The cutting edge is divided into multiple segments including first and second part edges, a concave curve, and a convex curve. This segmentation allows each portion to perform a specific function in directing cutting forces toward the center, resolving the drift issue while maintaining manufacturability through standardized geometries.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the cutting edge are given different geometries to perform different functions. The first part edge and concave curve direct forces from one side, while the second part edge and convex curve handle forces from the other side. This local differentiation ensures balanced force distribution across the cutting edge, preventing drill drift.

Inventive Principle:

Principle #3Local quality

2Productivity

If conventional cutting edges with convex and concave curves are used, then chip formation occurs, but the sudden change from concave to convex portions creates high stress areas and unsmooth chip formation

Engineering Contradiction:

Improvechip formation capabilityVSAvoidchip formation smoothness

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

Both the concave and convex portions are designed with curved geometries rather than sharp transitions. The concave curve has a first radius of curvature and the convex curve has a second radius of curvature, creating a gradual transition that eliminates sudden stress changes and produces smooth chip formation throughout the cutting process.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Productivity

If conventional drill inserts are used, then drilling can be performed, but chips may split into smaller fragments that go around the drill tool and ruin the surface finish

Engineering Contradiction:

Improvedrilling capabilityVSAvoidsurface finish degradation

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The radii of curvature of the concave and convex portions are specifically optimized to control chip formation characteristics. By adjusting these curvature parameters, complete chips are formed that are guided into the flute rather than fragmenting, thereby preventing surface finish degradation while maintaining drilling productivity.

Inventive Principle:

Principle #35Parameter changes

4Manufacturing precision

If the drill insert is designed to prevent drifting, then centering accuracy improves, but the complexity of the cutting edge design increases

Engineering Contradiction:

Improvedrill centering accuracyVSAvoidcutting edge geometry complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The cutting edge employs asymmetric geometry with a concave curve on one side and a convex curve on the other side, each with different radii of curvature. This asymmetric design is optimized to direct cutting forces toward the center, achieving precise centering accuracy while the symmetry of having four identical cutting edges simplifies overall manufacturing.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentUS9993881B2Idexable drill insert

Publication Date: 2018.06.12 KENNAMETAL INDIA

AI summary

The present disclosure relates to a quadrangular indexable drill insert. The drill insert includes a substantially flat top surface, a bottom surface and a side surface adjoining the top and bottom surfaces. The side surface comprises four identical cutting edges intersecting the top surface; each cutting edge comprises a first part edge oriented inwardly towards axis of the drill body. A second part edge tangential to an imaginary inscribed circle diameter connected to the first part edge through a convex curve. A third part connected to the second part edge through concave curve and a fourth part edge connected to the third part edge though a convex curve. The insert further includes a curved nose portion at four corners, each adjoining a first part edge of one cutting edge with a fourth part edge of a succeeding cutting edge.