Four-Edged Drill Geometry for Chip Control and Self-Centering
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Solution Overview
Problem
Existing four-edged drills face challenges in machining difficult-to-cut cast and light metal materials, particularly in engine construction, due to uneven cutting load distribution and chip build-up during high feed rates, leading to reduced tool life and accuracy.
Innovation Solution
A four-edged drill design with long main cutting edges divided into outer and inner partial cutting edges, where the inner partial cutting edges have a greater cutting height than the outer partial cutting edges, allowing for self-centering and optimal load distribution, reducing wear and improving chip drainage through the creation of two narrower chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If long main cutting edges extend to the center of the drill tip to enable drilling into solid material, then the drill can penetrate solid workpiece material, but the chisel edge connecting the long main cutting edges exerts only pressure and friction without cutting effect, hindering drilling into solid material
Solution Approach 1:
The long main cutting edges are segmented into outer partial cutting edges and inner partial cutting edges with different cutting heights. The inner partial cutting edges have greater cutting height and perform the cutting action into solid material, while the outer partial cutting edges have smaller cutting height and perform finishing. This segmentation eliminates the ineffective chisel edge pressure mechanism and distributes the cutting function across multiple edges.
Solution Approach 2:
Different sections of the main cutting edges are given different cutting heights to perform different functions. The inner partial cutting edges have greater cutting height for penetrating solid material, while the outer partial cutting edges have smaller cutting height for finishing. This local differentiation optimizes the cutting action at different radial positions.
2Productivity
If cutting load is distributed across four cutting edges with two long main cutting edges, then the drill can handle high feed rates, but the larger chip cross-section from wider chips created on long main cutting edges leads to chip jamming during deep drilling
Solution Approach 1:
The long main cutting edges are divided into outer and inner partial cutting edges that create narrower chips compared to conventional single-lip drills. This segmentation of the cutting action produces smaller chip cross-sections that can be effectively evacuated through the chip flutes, preventing chip jamming during deep hole drilling while maintaining high feed rates.
3Device complexity
If main cutting edges are completely straight and lie in front of a diametrical plane, then the drill structure is simplified, but uneven wear occurs on the long main cutting edges leading to premature tool failure
Solution Approach 1:
The main cutting edges are segmented into outer and inner partial cutting edges with different cutting heights. This segmentation allows each section to perform optimized cutting functions, distributing the cutting load more evenly across all four main cutting edges (two long and two short). The inner partial cutting edges engage first to create the hole, followed by the outer partial cutting edges for finishing, which equalizes wear across all cutting edges and prevents premature failure of any single edge.
4Productivity
If no pre-drilling guidance is used to simplify the drilling process, then the drilling operation becomes more efficient, but maintaining concentricity and stability in deep hole drilling becomes challenging
Solution Approach 1:
The drill employs four main cutting edges (two long and two short) arranged symmetrically, with the long main cutting edges further segmented into inner and outer partial cutting edges. This multi-edge configuration provides inherent guidance and self-centering capability during drilling, allowing the drill to maintain concentricity and stability in deep hole drilling without requiring pre-drilling guidance, thereby improving both efficiency and precision.
Data Source
Figure 1~10
Figure 11
Figure 12~15
AI summary
The invention relates to a four-edged drill (10) having two long main cutting edges (33), arranged in a point-symmetric manner with regard to the axis of rotation (11), which each extend from an outer circumferential cutting corner (31c) to a chisel edge (34) in the middle of the drill tip (11), and two short main cutting edges (30), arranged in a point-symmetric manner with regard to the axis of rotation (11), which each extend from an outer circumferential cutting corner (30c) in the direction of the middle of the drill tip (11). According to the invention, each long main cutting edge (33) has an outer partial cutting edge (31), extending from the cutting corner (31c) as far as a shoulder (31d), and an inner partial cutting edge (32), extending from the shoulder (31d) as far as the chisel edge (34), said inner partial cutting edge (32) having a greater cutting height (Δx) than the outer partial cutting edge (31) and the short main cutting edges (30).