Drill Bit Chip-Starting Shoulders for Friction Reduction
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Solution Overview
Problem
Drills with large core diameters face issues with built-up edges and chip removal, leading to increased friction, thermal loads, and reduced positioning accuracy when machining soft and high-strength materials, due to the interaction between the main cutting edge, thinning, and chip flute geometry.
Innovation Solution
A drill design featuring a central axis with main and central cutting edges that transition into a chisel edge, incorporating a point thinning with a continuously decreasing axial angle, and arc-shaped central cutting edges that bulge into the chip space, reducing friction and thermal loads by optimizing chip formation and removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a large core diameter is used in the drill, then the drill can machine harder materials, but built-up edges form more easily and chip removal is impaired
Solution Approach 1:
The patent applies point thinning specifically at the chisel edge (the center of the drill tip) while maintaining the full core diameter elsewhere. This local modification reduces friction and prevents built-up edge formation exactly where chips are generated, without compromising the overall structural strength of the drill body.
Solution Approach 2:
The chip-starting shoulders are pre-formed at specific locations on the rake face to guide chips into the flute channels before they can cause problems. This preliminary chip direction control prevents chip congestion and built-up edge formation in advance.
2Object-generated harmful factors
If the chisel edge is shortened by thinning the point, then built-up edge formation is reduced, but chip evacuation becomes more difficult
Solution Approach 1:
The patent introduces chip-starting shoulders that extend in the axial direction from the rake face, creating a three-dimensional chip guidance structure. This axial dimension provides a clear path for chips to follow into the flute channels, solving the evacuation problem without requiring excessive point thinning.
Solution Approach 2:
The chip-starting shoulders act as intermediary structures between the cutting edges and the flute channels. They mediate chip flow by providing a transition zone that smoothly guides chips from the cutting zone into the evacuation paths, preventing chip congestion.
3Object-generated harmful factors
If point thinning is increased to reduce built-up edges, then friction is reduced, but chip width exceeds flute depth and evacuation fails
Solution Approach 1:
Instead of uniformly increasing point thinning across the entire chisel edge, the patent applies chip-starting shoulders only at specific locations on the rake face. This localized approach reduces friction where needed while maintaining adequate chip width control through the shoulders' geometric constraints.
Solution Approach 2:
The chip-starting shoulders are positioned to intercept chips at their formation stage, preliminarily directing them into the flute channels before the chips can grow too wide. This preemptive chip guidance prevents the width-depth ratio problem before it occurs.
4Ease of operation
If the drill is forced off-axis during initial drilling, then positioning accuracy is impaired, but this is caused by built-up edges creating undefined cutting edge geometry
Solution Approach 1:
The patent applies point thinning and chip-starting shoulders specifically at the chisel edge region where cutting edge definition is most critical for initial drilling. This localized geometric control ensures stable chip formation and prevents built-up edges that would otherwise cause axis deviation.
Solution Approach 2:
The chip-starting shoulders are pre-formed to establish defined chip flow paths from the very beginning of the drilling operation. This preliminary geometric definition prevents the formation of built-up edges that would create undefined cutting edge geometry and cause positioning errors.
Data Source
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AI summary
The invention relates to a drill bit (1) having a center axis (11), a front face, a peripheral surface, at least two main cutting lips (17, 17') provided on the front face (3), at least two brad points (19, 19') , rake faces (37, 39), assigned to the at least two main cutting lips (17, 17') and the at least two brad points (19, 19'), flutes, at least one chisel edge, a recessed portion, and swarf guide shoulders (23a, 23b) which are assigned at least to the rake faces (39) of the at least two brad points (19, 19'). The drill bit (1) is characterized in that near the recessed portion the angle (y1, y2) between the swarf guide shoulder (23a, 23b) and the centre axis (11) diminishes as distance from the front face increases.