Octagonal Cutting Insert for Inside Right Angle Corners
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Solution Overview
Problem
Existing cutting tool inserts are limited in their indexability and geometry, making it difficult to efficiently cut inside right angle corners, particularly those requiring more than four indexable positions.
Innovation Solution
A cutting tool insert with eight identical cutting edges, arranged symmetrically on two side surfaces, each comprising a first and second cutting edge portion with a corner edge, allowing for eight times indexability and enabling the cutting of inside right angle corners with a corner angle between 75 to 90 degrees, providing strong cutting edges and suitable relief angles to prevent chip entrapment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a cutting tool insert has two opposite rhombus side surfaces with four cutting edges, then it can cut inside right angle corners, but it is only indexable four times
Solution Approach 1:
The cutting tool insert is divided into two substantially identical side surfaces, each containing four cutting edges arranged at corner portions. This segmentation allows the insert to be indexed eight times (four edges × two surfaces), doubling the indexability compared to conventional four-edge inserts while maintaining a manageable geometric structure.
Solution Approach 2:
The cutting edges are arranged asymmetrically at the corner portions of the insert body, with each cutting edge having a first cutting edge portion and a second cutting edge portion forming a corner angle. This asymmetric corner arrangement enables the insert to effectively cut inside right angle corners while achieving eight-times indexability.
2Strength
If the corner angle between first and second cutting edge portions is too small, then the cutting edge is stronger, but chip entrapment occurs
Solution Approach 1:
The corner angle between the first and second cutting edge portions is optimized within a specific range (45° to 90°). This parameter optimization balances two competing requirements: a smaller corner angle provides stronger cutting edges, while a larger corner angle prevents chip entrapment by providing adequate relief. The patent identifies the optimal range that simultaneously satisfies both requirements.
Solution Approach 2:
The cutting edge geometry is designed with different local characteristics: the first cutting edge portion has a specific orientation for engaging the workpiece, while the second cutting edge portion provides relief and chip flow path. This local differentiation of geometry ensures both cutting edge strength and chip evacuation capability.
3Adaptability or versatility
If the cutting tool insert requires mirror-image versions for left and right hand tool holders, then it can fit specific holders, but the device complexity increases
Solution Approach 1:
The cutting tool insert is designed with substantially identical side surfaces and symmetric corner arrangements, making it universally compatible with both left-hand and right-hand tool holders. A single insert design can be used in either holder type, eliminating the need for separate mirror-image versions and reducing inventory complexity.
Solution Approach 2:
The asymmetric corner arrangement at each side surface, when combined with the symmetry between the two side surfaces, creates a universal insert design that adapts to different holder configurations without requiring mirror-image variants.
Data Source
Figure 1a~1b
Figure 1c
Figure 2
AI summary
Herein a cutting tool insert (2) is disclosed. The insert (2) comprises eight identical cutting edges (14). Each separate cutting edge (14) comprises a first cutting edge portion (16) and a second cutting edge portion (18). A corner angle between the first cutting edge portion (16) and the second cutting edge portion (18) is within a range of 75 to < 90 degrees. The first cutting edge portion (16) and the second cutting edge portion (18) have substantially the same length to provide a substantially equal cutting depth. Seen along the centre axis (4) a first angle within a range of 14 +/- 9 degrees is formed between a first imaginary line extending from the centre axis (4) to a corner point at the first side surface (8) and a second imaginary line extending from the centre axis (4) to an adjacent corner point (24) at the second side surface (10). Further a cutting tool insert holder is disclosed.