Indexable Insert Cutting Edge Geometry for Drilling Centering
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Solution Overview
Problem
Existing square indexable inserts for solid drills face challenges in cutting properties and centering during drilling, with variable wear along active cutting edges and difficulties in centering, particularly when using square indexable inserts compared to trigon indexable inserts.
Innovation Solution
The cutting edge geometry is varied by adjusting the clearance angle along the cutting edges, with increases from 5° to 11° and decreases, and an asymmetric height profile, allowing for optimized cutting properties and reduced cutting resistance, while the rake angle remains constant, influencing centering and wear behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the clearance angle is increased to reduce cutting resistance, then the cutting properties are improved, but the strength in the cutting corner area is reduced
Solution Approach 1:
The patent applies local quality by varying the clearance angle along the cutting edge length. The clearance angle is smaller (e.g., 5°) near the cutting corner to maintain strength, and larger (e.g., 11°) in the middle section to reduce cutting resistance. This spatial variation of geometric parameters optimizes both strength and cutting efficiency in different locations of the same cutting edge.
Solution Approach 2:
The patent introduces dynamic characteristics by making the clearance angle variable rather than constant. The asymmetric profile creates different clearance angles at different positions and during different stages of cutting, allowing the cutting edge to adapt its geometry to the varying mechanical conditions along its path.
2Ease of manufacture
If square indexable inserts are used, then the manufacturing and clamping are simplified, but the centering during drilling deteriorates
Solution Approach 1:
The patent applies asymmetry by creating an asymmetric height profile of the cutting edges relative to the support base. The cutting edges have different heights at different positions, forming an asymmetric configuration that generates centering forces during drilling. This asymmetric geometry compensates for the symmetric square shape's poor centering characteristics while maintaining ease of manufacture.
3Productivity
If the cutting edge height is increased to improve cutting properties, then the cutting performance is enhanced, but the wedge angle increases and cutting resistance increases
Solution Approach 1:
The patent applies local quality by creating different cutting edge heights at different positions along the cutting edge. The cutting edge height varies asymmetrically, with maximum height in the middle section where it contributes to cutting performance, and smaller heights near the corners where excessive height would increase wedge angle and cutting resistance.
Data Source
Figure 1a
Figure 1b
Figure 2a~2c
AI summary
The invention relates to an indexable insert for solid drills comprising four identical cutting edges (30) arranged at a distance above a supporting base (42) and each extending between two cutting-edge corners (28', 28'). The cutting edges are each bounded by a cutting face (46) and a clearance face (48), with the inclusion of a wedge angle (b). Of the cutting edges (30), one in each case is in an active operating position during the drilling operation. To permit optimum adaptation to the cutting conditions and drilling characteristics, varying over the length of the cutting edge of the drilling tool, it is proposed according to the invention that the height (h) of the four cutting edges (30), measured from the plane of the supporting base (42), and/or the clearance angle (a) varies over the length of the respective cutting edges (30).