Twist Drill Round Chamfers for Deep-Hole Friction and Vibration
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Solution Overview
Problem
Conventional twist drills with round chamfers experience high friction and vibration during deep-hole drilling, leading to premature breakage, and face challenges in wear detection and lubricant distribution, especially when the ratio of flute section length to nominal diameter is high.
Innovation Solution
The twist drill design features round chamfers with an inclination angle greater than the helix angle of the chip flutes, creating gaps between adjacent chamfers that allow better lubricant access and chip clearance, reducing friction and improving wear detection by shifting the position of chamfers relative to cutting edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If round chamfers are provided on the cutting back of the drill, then the drill guidance and borehole quality are improved, but friction and vibration increase leading to premature breakage
Solution Approach 1:
The patent applies local quality by providing round chamfers only at specific locations on the cutting back rather than uniformly across the entire surface. The chamfers are positioned at predetermined locations and angles, creating localized guide surfaces that improve borehole quality without causing friction and vibration along the entire drill length. This selective application of round chamfers resolves the contradiction by providing guidance where needed while minimizing harmful friction elsewhere.
2Manufacturing precision
If the drill diameter defined by the cutting back is equal to or just slightly smaller than the nominal diameter, then guidance is improved, but friction increases significantly
Solution Approach 1:
The patent implements local quality by creating localized contact areas through round chamfers at specific positions on the cutting back. Instead of having the entire cutting back surface contact the borehole wall, only specific localized regions with round chamfers engage with the wall, providing guidance while minimizing the total contact area and thus reducing frictional energy loss.
3Loss of energy
If the land diameter is significantly smaller than the nominal diameter, then friction is reduced, but the drill oscillates or vibrates in the hole
Solution Approach 1:
The patent applies local quality by providing round chamfers at specific locations on the cutting back rather than uniformly reducing the entire land diameter. This creates localized guide surfaces that provide stability through targeted contact with the borehole wall, preventing oscillation and vibration while maintaining a smaller overall land diameter to reduce friction.
4Manufacturing precision
If multiple round chamfers are arranged on the cutting back, then guidance is improved, but chip clearance becomes difficult and lubricant distribution is poor
Solution Approach 1:
The patent implements local quality by positioning round chamfers at specific predetermined locations and angles on the cutting back, rather than uniformly distributing them. This strategic localization ensures that round chamfers provide guidance where most needed while maintaining adequate spacing and orientation for chip clearance and lubricant flow, preventing chip jamming between multiple chamfers.
Data Source
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AI summary
The present invention relates to a twist drill comprising a shaft (2) and a flute portion (3), which extends between a drill tip (4) and the shaft (2) and has at least two flutes (5), which run helically around it at an angle of twist (α), are separated from one another by two webs (6) and have a land (9) extending between the flutes (5) on the circumference of the flute portion (3). In order to provide a twist drill that has the features mentioned at the beginning, has better lubrication of the round bevels, less wear, improved guidance and improved concentricity, it is proposed according to the invention that at least two round bevels (11) that are spaced apart from one another are provided on each land (9) and extend on the land (9) at an angle of inclination (β) in relation to the drill axis (10) that is greater than the angle of twist (α) but less than 90°.