Drill With Curved Chisel Edge And Negative Rake Angles
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Solution Overview
Problem
Existing drills used for machining, particularly those with a positive rake angle at the cutting edge tip, are prone to premature damage when machining hard workpieces like cast iron, leading to reduced hole straightness and increased risk of cutting edge damage.
Innovation Solution
A drill design featuring a curved chisel edge with a pair of cutting edges, where the second cutting edge has a negative rake angle greater in absolute value than the first, and a rake face with specific angle configurations to distribute loads and reduce stress on the cutting edge, enhancing durability and straightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a positive rake angle is used at the cutting edge tip to maximize hole straightness, then hole straightness is improved, but the cutting edge becomes prone to premature damage
Solution Approach 1:
The patent applies different rake angles to different regions of the cutting edge. The tip region (first region) has a first rake angle optimized for hole straightness, while the body region (second region) has a second rake angle optimized for damage resistance. This local differentiation allows each region to perform its specific function optimally without compromising the other.
Solution Approach 2:
The cutting edge is segmented into multiple regions with distinct rake angle characteristics. The first region (tip) and second region (body) are treated as separate functional zones, each with optimized geometry for its specific role in the cutting process.
2Productivity
If a conventional drill design is used for hard workpieces, then machining capability is maintained, but cutting edge damage occurs prematurely
Solution Approach 1:
The patent changes the geometric parameters of the cutting edge by implementing a multi-region rake angle system. The first rake angle and second rake angle are specifically optimized for machining hard workpieces, altering the stress distribution and contact mechanics to prevent premature damage while maintaining effective cutting.
3Manufacturing precision
If the chisel edge angle is increased to 80-100 degrees to maximize hole straightness, then hole straightness is improved, but the risk of cutting edge damage increases
Solution Approach 1:
Different regions of the cutting edge are assigned different rake angle properties. The tip region maintains geometry optimized for hole straightness, while the body region adopts geometry optimized for damage resistance, thereby locally addressing the conflicting requirements.
Solution Approach 2:
The rake angle parameters are specifically adjusted in different regions. The first rake angle and second rake angle are set to values that collectively reduce damage risk while preserving hole straightness, representing a parameter optimization strategy.
Data Source
AI summary
A drill according to a non-limiting aspect may have a body, a cutting edge, a rake face, and a groove. The cutting edge may have a curved chisel edge, a pair of first cutting edges, and a pair of second cutting edges. The second cutting edge may have a first portion extending from the chisel edge and a second portion extending from the first portion toward the first cutting edge. The rake face may have a first region extending from the first portion and a second region extending from the second portion. A first rake angle of the first region may be zero or a negative value. A second rake angle of the second region may be a negative value. An absolute value of the second rake angle may be greater than an absolute value of the first rake angle.