Drill Cutting Edge Geometry for Chip Flow and Chipping Resistance
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Solution Overview
Problem
Existing drills experience wear and chipping at the outer peripheral end portion of the cutting edge, leading to reduced tool life and compromised machined surface quality due to chipping, especially at the intersecting ridgeline between the margin and the rake face, resulting in increased cutting resistance and potential breaking.
Innovation Solution
A drill design featuring a chip removal groove with a concave and convex wall face configuration, where the second wall face extends toward the inner periphery, forming a cutting edge with a larger radius of curvature and honing faces to secure strength and prevent chipping, and the margin portion is included in a land portion to reduce wear, with specific tilt and inclination angles to maintain sharpness and prevent breaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cutting edge is formed with a concave curve shape to curl chips and improve chip removal, then chip removal performance is improved, but chipping occurs at the outer peripheral end portion of the cutting edge leading to margin wear and reduced tool life
Solution Approach 1:
The patent applies different geometric characteristics to different portions of the cutting edge. The inner peripheral portion has a concave curve shape for effective chip curling, while the outer peripheral portion transitions to a convex curve shape with increased radius of curvature to prevent chipping. This local differentiation allows each region to optimize its function without compromising the other.
Solution Approach 2:
The patent changes the radius of curvature parameter along the cutting edge from the inner periphery to the outer periphery. The radius of curvature increases progressively, being smaller at the inner peripheral end for sharp cutting and chip curling, and larger at the outer peripheral end to reduce stress concentration and prevent chipping. This gradual parameter change resolves the contradiction between chip removal effectiveness and edge durability.
2Reliability
If the radius of curvature of the cutting edge is increased to prevent chipping, then margin wear is reduced, but cutting resistance increases and breaking may occur
Solution Approach 1:
Different radius of curvature values are assigned to different locations along the cutting edge. The inner peripheral portion maintains a smaller radius for sharpness and cutting effectiveness, while the outer peripheral portion has a larger radius for chipping prevention. This spatial differentiation of geometric parameters allows simultaneous optimization of both cutting performance and edge strength.
Solution Approach 2:
Instead of increasing the radius of curvature uniformly across the entire cutting edge, the patent applies the larger radius only partially to the outer peripheral portion where chipping is most problematic. The inner peripheral portion retains the smaller radius necessary for effective cutting, thus avoiding excessive action that would compromise cutting sharpness while still providing protection where needed.
Data Source
AI summary
In this drill, a wall face of a chip removal groove includes a first wall face having a concave curve shape and a second wall face having a straight line shape in a cross section orthogonal to an axis of the drill main body, an extension line of a straight line of the second wall face extends in a direction opposite to a drill rotation direction as the straight line of the second wall face goes to an outer periphery side of the drill main body with respect to a radius line connecting an outer peripheral end of the second wall face and the axis with each other, the cutting edge includes a first cutting edge having a concave curve shape and a second cutting edge having a straight line shape which intersects with the first cutting edge at an obtuse angle.