Tool Holder Stress Relief Surface Curvature

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Solution Overview

Problem

Existing tool holders with stress relief surfaces in rotary machining operations experience peak tensile stresses at the corner intersection of stress relief and pocket peripheral surfaces, leading to high stress concentrations.

Innovation Solution

A tool holder design featuring a first stress relief surface with a concave shape and a second stress relief surface with a convex shape in cross-section, where the second surface is formed by non-abrasive machining, providing a smooth transition and reducing peak tensile stresses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stress or pressure

If stress relief surfaces are added to reduce tensile and compressive stresses, then stress relief is improved, but peak stress concentrations occur at corner intersections

Engineering Contradiction:

Improvetensile and compressive stressesVSAvoidpeak stress concentration

Core Design Contradiction:

Stress or pressureVSStrength

Solution Approach 1:

The patent applies curvature by replacing the sharp corner intersection with a convex surface that has a positive radius of curvature. This convex shape smoothly transitions between the first stress relief surface and the pocket peripheral surface, eliminating the stress concentration that occurs at sharp corners. The curved geometry redistributes stresses more evenly across the transition zone.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The patent applies different surface geometries to different locations: a concave first stress relief surface for general stress relief, and a convex second surface specifically at the corner intersection for stress concentration reduction. This localized differentiation of surface quality addresses the specific stress distribution needs of each region.

Inventive Principle:

Principle #3Local quality

2Stress or pressure

If corner intersection surfaces with chamfer or concave shape are used, then stress relief is provided, but peak stress values occur immediately adjacent to these surfaces

Engineering Contradiction:

Improvestress distributionVSAvoidpeak tensile stress value

Core Design Contradiction:

Stress or pressureVSStrength

Solution Approach 1:

The patent replaces the concave corner intersection surface with a convex surface having a positive radius of curvature. This convex geometry creates a smooth outward bulge that distributes stresses more evenly, preventing the peak stress concentration that occurs at the sharp transitions of chamfer or concave surfaces.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The patent inverts the conventional approach by using a convex surface instead of a concave or chamfered surface at the corner intersection. This inversion of the surface geometry fundamentally changes the stress distribution pattern, transforming stress concentration into stress relief.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS10005141B2Tool holder having insert receiving pocket with stress relief surfaces

Publication Date: 2018.06.26 ISCAR LTD

AI summary

A tool holder has a tool body with at least one pocket for receiving at least one cutting insert. The at least one pocket has a support surface and an abutment surface transverse thereto, and a first stress relief surface located between the support surface and the abutment surface. The first stress relief surface extends along a first axis towards a first pocket peripheral surface. A second stress relief surface is formed between the first stress relief surface and the first pocket peripheral surface. The second stress relief surface has a convex shape in a cross-sectional view taken in a second plane containing the first axis. The convex shape may have a radius greater than 0.3 mm.