Drill With Segmented Main And Auxiliary Cutting Edges
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Solution Overview
Problem
Conventional drills with two cutting edges efficiently discharge machining dust but wear quickly, while four-edge drills maintain edge wear slowly but degrade dust discharge efficiency, making it difficult to increase feed speed and reduce boring time.
Innovation Solution
A drill design featuring a pair of main cutting edges and a pair of auxiliary cutting edges, where the auxiliary edges are positioned differently in the circumferential direction, with point angles increasing more rapidly than the main edges, allowing the cutting range to widen as wear progresses, enabling both high cutting performance and extended service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a two-edge drill is used, then machining dust is efficiently discharged and feed speed can be increased, but wear of the cutting edges progresses relatively quickly
Solution Approach 1:
The drill is segmented into two distinct pairs of cutting edges: main cutting edges for roughing operations and auxiliary cutting edges for finishing operations. This segmentation allows each pair to be optimized for its specific function, with the main edges handling material removal and the auxiliary edges providing precise finishing, thereby extending overall drill service life while maintaining high productivity
Solution Approach 2:
The drill transitions dynamically from two-edge operation to four-edge operation as wear progresses. Initially, only the main cutting edges are active for efficient material removal. As the main edges wear, the auxiliary edges gradually engage to maintain cutting performance, creating a dynamic adaptation that extends the drill's usable life without compromising productivity
2Reliability
If a four-edge drill is used, then wear of the cutting edges progresses relatively slowly, but grooves cannot be set large and discharging efficiency for machining dust is degraded
Solution Approach 1:
The four cutting edges are segmented into two functional groups: main cutting edges with larger grooves for efficient dust discharge during roughing, and auxiliary cutting edges with smaller grooves for precise finishing. This segmentation resolves the contradiction by allowing large grooves to exist only where needed for productivity, while additional edges provide extended service life
Solution Approach 2:
Different regions of the drill have different groove sizes optimized for their specific functions. The main cutting edges have larger grooves positioned to handle high-volume dust discharge during roughing operations, while the auxiliary cutting edges have appropriately sized grooves for finishing operations, achieving both high productivity and extended service life through localized optimization
3Manufacturing precision
If a four-edge drill is used, then holes can be finished with high quality for a long term, but it is difficult to increase the feed speed and decrease the boring time
Solution Approach 1:
The main cutting edges perform preliminary roughing operations to remove the majority of material quickly, preparing the hole for finishing. This preliminary action allows the subsequent auxiliary edges to focus solely on high-precision finishing, achieving both reduced boring time and high hole quality without the compromise faced by conventional four-edge drills
Data Source
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Figure 6A~7
AI summary
A drill includes a pair of main cutting edges (A) extending from a distal portion of the drill to a position (G) close to a proximal end of the drill to entirely define a two-edge configuration, and a pair of auxiliary cutting edges (B) extending between positions at the distal and proximal sides (F and G) of a maximum diameter position (E) to partly define a four-edge configuration. A ridgeline (B1) of each auxiliary cutting edge (B) is located within an angle smaller than 90° from a ridgeline (A1) of the corresponding main cutting edge (A) toward the rear in a rotation direction of the drill. The point angle of the auxiliary cutting edges (B) increases at a higher rate than the point angle of the main cutting edges (A) in a predetermined range from the maximum diameter position (E) toward a distal end of the drill.