Segmented Drill Cutting Edges for Low-Burr Shoulder Protection
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Solution Overview
Problem
Conventional drilling tools face issues where the shoulder part is damaged during machining, and methods to reduce this damage, such as providing an R part or chamfer, lead to increased cutting resistance and edge abrasion, as well as larger exit burrs.
Innovation Solution
A drilling tool with multiple cutting edges and honing portions, where the third honing portion is larger than the first, reducing shoulder damage and cutting resistance while minimizing exit burrs through a double chamfer shape and controlled honing sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an R part or chamfer is provided at the shoulder part of the tool, then the shoulder part damage is reduced, but the exit burr becomes large
Solution Approach 1:
The cutting edge is divided into multiple segments (first, second, and third cutting edges) with different functions. The first cutting edge performs primary cutting, while the second and third cutting edges work together to control exit burr formation. This segmentation allows each edge to be optimized for its specific function, reducing the need for large R parts or chamfers that cause burrs.
Solution Approach 2:
Different portions of the cutting edge are given different properties through selective honing. The first honing portion has a smaller honing size to maintain cutting sharpness, while the third honing portion has a larger honing size to strengthen the edge and reduce shoulder damage. This local differentiation resolves the contradiction between durability and precision.
2Manufacturing precision
If multiple projected edges are provided to reduce exit burr, then the exit burr is suppressed, but the cutting resistance and edge abrasion increase
Solution Approach 1:
Instead of uniformly adding multiple projected edges throughout the cutting edge, the invention applies different honing sizes to different portions. The first honing portion maintains a smaller size to minimize cutting resistance, while only the third honing portion has a larger size to control exit burr. This localized approach reduces overall cutting resistance compared to uniform multi-edge designs.
3Reliability
If the honing size of the third honing portion is made larger, then the third cutting edge strength is improved and shoulder damage is reduced, but the cutting resistance may increase
Solution Approach 1:
The invention strategically places the larger third honing portion only at the outermost cutting edge where it is most needed for strength and shoulder protection. The inner first and second honing portions maintain smaller sizes to minimize their contribution to cutting resistance. This localized honing strategy optimizes the strength-to-resistance ratio.
Solution Approach 2:
The cutting edge is segmented into three distinct zones with progressively larger honing sizes. This segmentation allows the third cutting edge to bear the primary load for shoulder protection while the first two edges handle the bulk of the cutting action with lower resistance. The segmented structure distributes functions to minimize overall cutting resistance while ensuring adequate strength where needed.
Data Source
AI summary
It is possible to reduce shoulder parts from being damaged while suppressing an increase in cutting resistance or abrasion of edges at a time of machining.A drilling tool for drilling machining includes: at least one major cutting edge; second cutting edges that are provided on an outer side of a tool radial direction of the major cutting edge; third cutting edges that are provided on the outer side of the tool radial direction of the second cutting edges; a first honing portion that is formed at the major cutting edge; second honing portions that are formed at the second cutting edges; and third honing portions that are formed at the third cutting edges. Honing sizes of the third honing portions are larger than a honing size of the first honing portion.