Two-Blade Drill Pyramid Tip Geometry for Hole Accuracy
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Solution Overview
Problem
Drills with chisel edges suffer from reduced rigidity, increased thrust loads, and poor hole accuracy due to orthogonal force components, while modifications like conical projecting parts either compromise centering or increase manufacturing costs.
Innovation Solution
A two-blade drill with a pyramid tip where the apex is on the center line and each edge's inclination angle is greater than half the tip angle, featuring concave pyramid surfaces, which removes the chisel edge and stabilizes cutting, reducing thrust loads and improving accuracy without increasing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a chisel edge is provided in the drill tip, then the drill can be manufactured using existing methods, but rigidity is reduced and thrust load increases
Solution Approach 1:
The invention extracts and removes the chisel edge from the drill tip geometry. By defining the drill tip with only two cutting edges meeting at an apex without a chisel edge, the patent eliminates the source of rigidity reduction and excessive thrust load while maintaining manufacturability through conventional drilling operations.
Solution Approach 2:
Instead of modifying the chisel edge to improve performance (as done in prior art), the invention inverts the approach by completely eliminating the chisel edge and using only two symmetric cutting edges. This inversion of the conventional drill geometry resolves the fundamental contradiction between manufacturability and edge rigidity.
2Device complexity
If a chisel edge is provided in the drill tip, then the drill structure is complete, but components of force orthogonal to thrust are generated reducing centering capability
Solution Approach 1:
The invention extracts the chisel edge and associated force-generating components from the drill tip. By using only two symmetric cutting edges meeting at an apex, the design eliminates orthogonal force components that cause poor centering, thereby improving hole accuracy while maintaining a complete and functional drill structure.
Solution Approach 2:
The invention employs asymmetric force distribution through symmetric geometry - two cutting edges are positioned symmetrically about the drill axis, which creates balanced force components that cancel orthogonal forces. This symmetric arrangement eliminates the centering problems associated with conventional chisel edge designs.
3Productivity
If the chisel edge is shortened by thinning to improve chip discharging, then chip discharging capability is improved, but edge rigidity is reduced
Solution Approach 1:
The invention extracts the chisel edge entirely, replacing it with two symmetric cutting edges that meet at an apex. This elimination of the chisel edge simultaneously improves chip discharging capability and maintains edge rigidity, resolving the contradiction between productivity and strength that plagues thinned chisel edge designs.
4Manufacturing precision
If a conical projecting part is added at the chisel position to prevent orthogonal forces, then centering capability is improved, but thrust load increases causing buckling
Solution Approach 1:
The invention extracts and eliminates the conical projecting part from the drill tip. By using only two symmetric cutting edges meeting at an apex, the design achieves centering capability through symmetric force distribution while avoiding the excessive thrust load and buckling problems caused by conical projections.
5Manufacturing precision
If a conical projecting part is added to the drill tip, then centering capability is improved, but manufacturing cost increases due to inability to use existing grinding methods
Solution Approach 1:
The invention extracts the conical projecting part from the drill tip geometry. By defining the drill with only two symmetric cutting edges meeting at an apex, the design maintains compatibility with existing drill grinding and manufacturing methods, eliminating the cost increase associated with conical projections while preserving centering capability.
Data Source
Figure 1~2
Figure 3~4
Figure 5(a)~5(c)
AI summary
TASK An inexpensive drill with high processing accuracy is provided. MEANS FOR SOLVING THE PROBLEM A chisel edge 11 of a tip 12 is removed, and a pyramid 1 is formed in that part, in which an inclination angle θ1 of each edge 4 extending from an apex P relative to a center line of the drill CL is formed to be larger than an angle θ2 that is one-half of a drill tip angle θ0, and so chisel steps are resolved and stable cutting becomes possible, thereby improving hole accuracy. Also, it is possible to form the pyramid 1 by grinding a tip of an existing drill by a grinder, so that a drill can be realized at a low cost.