Four-Edge Spiral Drill Geometry for Chip Control and Centering
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Solution Overview
Problem
Conventional drills face challenges in achieving a large advance while maintaining high precision, particularly in terms of roundness, diameter tolerance, and surface properties when drilling metallic workpieces, due to issues with chip jamming and centering accuracy.
Innovation Solution
The drill features at least four main cutting edges and/or three central cutting edge portions, which reduce chip size, improve guidance, and increase drilling advance with lower cutting pressure, along with a rotationally symmetric configuration and specific rake and clearance angles to enhance centering accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional drills with two main cutting edges and a chisel edge are used, then the structure is simple and easy to manufacture, but chip jamming occurs frequently and drilling precision deteriorates
Solution Approach 1:
The drill is segmented into four main cutting edges instead of two, with each edge responsible for cutting and chip formation. The chisel edge is replaced by additional cutting edges that extend toward the center, segmenting the chip removal function across multiple edges rather than relying on a single chisel edge configuration.
Solution Approach 2:
The cutting edges are configured to extend in the radial direction toward the drill axis, adding a dimensional aspect to chip removal. The main cutting edges have radial extents that allow them to cut material closer to the center, effectively utilizing the radial dimension to improve chip evacuation and reduce jamming.
2Measurement precision
If the chisel edge is used for centering, then the drill structure is simple, but friction increases and centering accuracy deteriorates
Solution Approach 1:
The chisel edge is extracted or removed from the drill configuration. Instead of using a chisel edge for centering, the patent employs main cutting edges that extend radially inward to perform both cutting and centering functions, eliminating the friction problems associated with chisel edge crushing action.
Solution Approach 2:
The geometry of the cutting edges is changed by specifying radial extents and angles (such as the half-angle alpha between 5° and 30°) that optimize both centering accuracy and cutting pressure distribution. This parameter optimization allows effective centering without excessive friction.
3Productivity
If fewer main cutting edges are used, then the device complexity is low, but drilling advance is limited and productivity is reduced
Solution Approach 1:
The drilling function is segmented into four main cutting edges, each contributing to material removal and advance. This segmentation allows for better distribution of cutting loads and improved chip evacuation, enabling faster drilling advance compared to conventional two-edge drills.
Solution Approach 2:
The main cutting edges are configured to work continuously along their radial extents, with each edge maintaining contact with the workpiece throughout the drilling process. This continuous cutting action across multiple edges maximizes material removal efficiency and drilling advance.
Data Source
AI summary
For improving a drill, in particular a spiral drill, comprising a base body extending substantially longitudinally in a direction axial to a drill axis, said base body comprising a drilling portion, wherein a radially inward core region in relation to the drill axis and a radially outer region are provided in the base body in the drilling portion, and the drilling portion comprises a plurality of spiral-shaped recesses in the outer region, and arranged between each two spiral-shaped recesses is a wall part, it is proposed that the drill comprises at least four main cutting edges, in particular exactly four main cutting edge and/or the drill comprises at least three central cutting edge portions.