Turning Insert Relief Geometry for Internal Boring Clearance
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Solution Overview
Problem
Existing turning tools for internal turning operations face challenges in achieving sufficient clearance without compromising cutting insert strength, particularly in machining small holes where space is limited, and often result in unfavorable cutting conditions due to tilting of cutting inserts.
Innovation Solution
A cutting insert design with a negative basic shape and a peripheral surface featuring a relief surface that extends less than 75% of the maximum thickness in a direction parallel to the central axis, maintaining strength while providing increased clearance by reducing the risk of rubbing between the relief surface and the machined surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the relief surface length is increased to provide clearance, then the clearance to the machined surface is improved, but the strength of the cutting insert deteriorates
Solution Approach 1:
The patent changes the geometric parameter of the relief surface by limiting its axial extension to less than 75% of the maximum insert thickness. This parameter optimization provides sufficient clearance for internal turning operations while preserving the structural integrity and strength of the cutting insert.
2Manufacturing precision
If the cutting insert is tilted to achieve clearance, then the accessibility to the machined surface is improved, but the cutting conditions deteriorate
Solution Approach 1:
The patent applies local quality by providing clearance only where needed through the strategic design of the relief surface geometry. The relief surface extends axially less than 75% of the maximum thickness, creating localized clearance in the critical area while maintaining proper insert orientation and favorable cutting conditions throughout.
3Manufacturing precision
If a positive cutting insert is used for internal turning, then the clearance with the workpiece surface is improved, but the cutting edge strength deteriorates
Solution Approach 1:
The patent inverts the conventional approach by using a negative basic shape insert (typically used for external turning) for internal turning operations. By combining this negative shape with a relief surface that extends less than 75% of the maximum thickness axially, the patent achieves both strong cutting edges and adequate clearance, reversing the traditional assumption that positive inserts are required for internal turning.
Data Source
Figure 1~2
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AI summary
The invention relates to a cutting insert (1, 40, 90) for a turning tool, the cutting insert comprising a first side (2) and a second side (3) arranged opposite each other and facing opposite directions, the first and second sides generally extending in respective first and second planes (Pl, P2) that are parallel to each other, wherein the first side (2) comprises a first rake face (11). A central axis (L) of the cutting insert extends from the first side (2) to the second side (3) in a direction perpendicular to the first and second planes (Pl, P2). The cutting insert comprises a peripheral surface (4) connecting the first side (2) and the second side (3), wherein the peripheral surface (4) includes a first relief surface (7) extending in parallel, or substantially in parallel, to the central axis. A first cutting edge (5) is arranged at the intersection between the first relief surface (7) and the first rake face (11), wherein the first cutting edge (5) comprises a first nose cutting edge (51). The cutting insert has a maximum thickness (t) measured from the first side (2) to the second side (3) in a direction parallel to the central axis (L), and the first relief surface (7) adjacent the first nose cutting edge (51) has a length of extension (h) in a direction parallel to the central axis (L) that is less than 75% of the maximum thickness (t) of the cutting insert (1). The invention also relates to a turning tool (10) comprising such cutting insert.