Indexable Drill Insert Asymmetric Cutting Edges Centering
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Solution Overview
Problem
Conventional quadrangular indexible drill inserts with rectangular cutting edges tend to drift from the center during drilling, leading to narrow walls and surface rubbing issues, especially when drilling holes with diameters less than a predetermined value.
Innovation Solution
A quadrangular indexable drill insert with four identical cutting edges, featuring a flat top and bottom surface, inclined part edges, a curved nose portion, and a through hole for mounting, which directs forces to the drill axis, preventing drifting and including a chamfer to prevent surface rubbing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If rectangular cutting edges are used in conventional quadrangular indexible drill inserts, then the manufacturing and assembly process is simplified, but the drill drifts away from its center during drilling
Solution Approach 1:
The cutting edges are designed with asymmetric geometry relative to the drill axis, with specific inclination angles (first part edge inclined at 0.5°-5°, second part edge inclined at 5°-15°) that create force components directing the drill toward the center, eliminating the symmetry-induced drift problem while maintaining manufacturability
Solution Approach 2:
Different segments of each cutting edge have different geometric properties - the first part edge has a specific inclination angle for centering, the second part edge is tangential to the inscribed circle for cutting, and the third part edge extends away from the axis - optimizing local functions to achieve overall centering precision
2Device complexity
If conventional rectangular cutting edges are used, then the insert structure is simple, but narrow walls are created that are not feasible in practical applications
Solution Approach 1:
Curved nose portions of predetermined radius are added at the four corners of the insert, connecting the first part edge of one cutting edge with the third part edge of the succeeding cutting edge, which rounds the cutting path and enables the creation of wider, more practical wall geometries while maintaining the basic quadrangular insert structure
3Device complexity
If conventional drill inserts are used, then the design is straightforward, but the insert rubs the surface of the drilling hole when the diameter is less than a predetermined value
Solution Approach 1:
A chamfer is provided at the bottom edge of the drill insert, extracting the harmful rubbing action by creating a relieved edge that prevents the insert from contacting and rubbing the drilled hole surface, particularly beneficial for small diameter holes where this effect is more pronounced
4Force
If rectangular cutting edges act all over the drill body, then the cutting action is distributed, but the forces do not act exactly at the center causing drift
Solution Approach 1:
The cutting edge geometry is designed with specific local inclinations where the first part edge is inclined at 0.5°-5° and the second part edge is inclined at 5°-15° toward the axis, creating localized force components that direct the resultant cutting force toward the drill center, transforming the force distribution from uniform (causing drift) to targeted (achieving centering)
Data Source
AI summary
A quadrangular indexable drill insert includes a substantially flat top and bottom surfaces, a side surface adjoining the top and bottom surfaces, four identical cutting edges of the side surface intersecting the top surface, a through hole extending between the top and bottom surfaces, and a chamfer provided at the bottom edge of the drill insert. Each cutting edge includes a first part edge; a second part edge extending from the first part edge; a third part edge extending away from the central axis, the second and third part edges being joined together by a transition part edge having a concave curved portion and a convex curved portion; and a curved nose portion of predetermined radius disposed at a corner of the insert adjoining the first part edge of one cutting edge with the third part edge of a succeeding cutting edge of the four identical cutting edges.