Indexable Drill Insert Asymmetric Geometry Center Alignment
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Solution Overview
Problem
Conventional indexible drill inserts with rectangular cutting edges tend to drift from the center due to uneven cutting forces, leading to narrow walls and surface rubbing issues, especially when drilling holes with diameters less than a predetermined value.
Innovation Solution
A quadrangular indexible drill insert with four identical cutting edges, each comprising a first part edge tangent to a reference circle, a second part edge connected via a convex curved portion, a third part edge tangent to a smaller reference circle via a concave curved portion, and a convexly curved corner, disposed at specific inclination angles to maintain center alignment and prevent rubbing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If rectangular cutting edges are used in conventional indexible drill inserts, then the insert structure is simple and easy to manufacture, but the drill drifts away from its center due to uneven cutting forces
Solution Approach 1:
The cutting edges are designed with asymmetric geometry featuring convex and concave curved portions that create differential cutting forces. This asymmetry intentionally balances the overall cutting force distribution to act through the drill center, preventing drift while maintaining manufacturing simplicity through standardized insert forms.
Solution Approach 2:
The cutting edges incorporate convex curved portions and concave curved portions instead of straight rectangular edges. These curved geometries modify the force distribution during cutting, ensuring that the resultant cutting force passes through the center of the drill, thereby eliminating drill drift while keeping the insert structure relatively simple.
2Ease of manufacture
If rectangular cutting edges are used in conventional indexible drill inserts, then the insert is easy to manufacture, but narrow walls are created which are not feasible in practical applications
Solution Approach 1:
The convex curved portions at the leading edges of the cutting edges and the concave curved portions create a more favorable chip flow pattern and wall formation. This curvature produces broader, more feasible wall geometries in the drilled holes compared to sharp rectangular edges, while the overall insert remains simple to manufacture.
3Loss of time
If conventional indexible drill inserts are used, then assembly time is reduced through replaceable inserts, but surface rubbing occurs when drilling holes with diameter less than predetermined value
Solution Approach 1:
The convex curved portions at the leading edges of the cutting edges act as pilot edges that guide the insert into the workpiece and prevent rubbing on small diameter holes. The curved geometry ensures proper surface engagement before the main cutting edges engage, eliminating the rubbing problem while maintaining the quick-change insert advantage.
Solution Approach 2:
The convex curved leading portions of the cutting edges perform a preliminary guiding and breaking-in action before the main rectangular cutting portions engage the workpiece. This preliminary action prevents surface rubbing on small diameter holes, and the entire insert design maintains the benefit of quick replacement without assembly time penalty.
Data Source
AI summary
An insert includes four identical cutting edges disposed at the intersection of top and side surfaces surface. Each cutting edge includes a first part edge disposed tangent to a first reference circle aligned about the central mounting aperture; a second part edge extending from the first part edge, the second part edge being connected to the first part edge via a convex curved portion; a third part edge disposed tangent to a second reference circle aligned about the central mounting aperture, the second reference circle having a smaller diameter than the first reference circle, the third part edge being connected to the second part edge via a concave curved portion; and a convexly curved corner portion extending from the third part edge of one of the identical cutting edges to the first part edge of another one of the identical cutting edges.