Negative-Land Drill Geometry to Reduce Edge Chipping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Drills with existing cutting edge designs tend to experience chipping, leading to reduced durability and work-hardened cut surfaces, making subsequent processes like tapping and reaming difficult.
Innovation Solution
The drill design incorporates a rake face, negative land, and outer circumferential surface with specific geometric features such as recessed regions and curvature, which enhance the strength of the cutting edge and prevent work-hardening, including a first region where the space between upper and lower cutting edges widens towards the outer surface and a second region where it widens towards the rotation axis, along with additional features like upper cutting edge portions and a recessed return face.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cutting edge design is used, then the drill can perform basic drilling function, but the cutting edge is prone to chipping and has reduced durability
Solution Approach 1:
The negative land is divided into multiple regions (first region, second region, third region) with different geometric characteristics. Each region serves a specific function: the first region provides chip flow, the second region strengthens the cutting edge, and the third region controls chip formation. This segmentation allows optimization of each region independently to prevent chipping while maintaining durability.
Solution Approach 2:
Different portions of the negative land have different cross-sectional shapes and dimensions tailored to local requirements. The first region has a cross section that widens toward the outer circumferential surface for chip evacuation, the second region has a cross section that widens toward the rotation axis for cutting edge strength, and the third region has specific dimensions for chip control. This local quality differentiation prevents chipping in critical areas while maintaining overall durability.
2Ease of operation
If conventional cutting edge geometry is used, then drilling can be performed, but the cut surface becomes work-hardened making subsequent processes difficult
Solution Approach 1:
The negative land is segmented into regions that control chip flow and cutting action separately. The first region facilitates smooth chip flow that prevents abrupt chip breakage, while the second and third regions control the cutting edge geometry to reduce impact on the workpiece. This segmentation allows the cut surface to be formed with less work-hardening, improving subsequent processability.
Solution Approach 2:
Instead of designing the cutting edge to be as sharp and protruding as possible, the invention uses a recessed negative land that extends toward the rotation axis. This inverted approach, where the cutting edge is recessed rather than protruding, reduces the impact force on the workpiece and minimizes work-hardening of the cut surface, making subsequent operations easier.
3Strength
If the negative land is designed to prevent chipping, then cutting edge strength improves, but the geometry becomes more complex
Solution Approach 1:
The negative land is divided into three distinct regions, each with a specific function. The first region handles chip flow, the second region provides cutting edge strength through its cross-sectional geometry, and the third region controls chip formation. This segmentation allows each region to be optimized for its specific function, achieving high cutting edge strength while maintaining a systematic and manufacturable geometry.
Solution Approach 2:
The invention specifies precise parameter ranges for each region of the negative land, including cross-sectional dimensions, angles, and relative positions. By controlling these parameters within specific ranges, the cutting edge strength is optimized without requiring overly complex geometry. The parameters are designed to be achievable through conventional manufacturing processes.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A drill includes a rake face, a negative land, a flank face, and an outer circumferential surface. The negative land is continuous to the rake face. The flank face is continuous to the negative land. The outer circumferential surface is continuous to the rake face, the negative land, and the flank face. A ridgeline between the rake face and the negative land constitutes a lower cutting edge. A ridgeline between the flank face and the negative land constitutes an upper cutting edge. When viewed in a direction along a rotation axis of the drill, the negative land includes: a first region in which a space between the upper cutting edge and the lower cutting edge becomes wider toward the outer circumferential surface; and a second region which is continuous to the first region and in which the space becomes wider toward the rotation axis. In a cross section perpendicular to the rotation axis, the rake face includes a return face continuous to the outer circumferential surface, the return face being recessed opposite to a rotation direction of the drill. When a first boundary represents a boundary between the outer circumferential surface and the first region and a second boundary represents a boundary between the first region and the second region, a length of the first boundary is larger than a length of the second boundary in a direction parallel to the rotation axis. The second boundary is continuous to the return face.