Step Drill Groove Grinding for Favorable Step Edge Rake
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Solution Overview
Problem
Conventional step drills with convex blade parts at the cutting edge of the small-diameter portion tend to form cutting edges with large negative radial rake angles, leading to degraded cutting performance, including surface roughness failures and tearing during chamfering operations.
Innovation Solution
A step drill design featuring a first cutting edge with a convex blade part on the small-diameter portion and a second cutting edge that is substantially linearly formed towards the circumferential end of the step portion, with a grinding process involving two passes to shape the cutting edges, preventing interference and maintaining a favorable radial rake angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a grind stone with swing angle is used to form convex blade part, then convex blade part can be formed on cutting edge, but interference between grind stone and step portion is increased and cutting edge of step portion is formed with large negative radial rake angle
Solution Approach 1:
The groove grinding operation is segmented into two distinct passes: first pass grinds the groove in the small-diameter portion using a grind stone with swing angle to form the convex blade part; second pass grinds the groove in the step portion. This segmentation eliminates interference between the swing angle grind stone and the step portion, allowing precise control of the step portion cutting edge geometry
Solution Approach 2:
The convex blade part formation is performed as a preliminary action in the first grinding pass. By completing this shape formation beforehand, the subsequent second grinding pass can focus solely on forming the step portion cutting edge with the desired linear shape and appropriate radial rake angle, free from interference
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances cutting performance by preventing large negative radial rake angles, reducing surface roughness failures, and improving the quality of the cutting edges during drilling and chamfering operations.
Implementation Method 1
a first groove is ground toward an axis more shallowly than a desired web thickness to form a first cutting edge
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3A~3B
AI summary
A step drill and a manufacturing method for a step drill in which cutting performance of a cutting edge of a step portion can be enhanced are provided. A groove (5) includes a first ground portion (50) forming an area embracing a second cutting edge (30) of the step portion (3) and a second ground portion (51) forming an area on the heel (7) side of the step portion (3) relative to the first ground portion (50). Therefore, a convex blade part (20a) can be formed on a first cutting edge (20) by performing grinding with the first ground portion (50) and the second ground portion (51) intersecting with each other in two passes of groove grinding comprised of a step of grinding the first ground portion (50) and a step of grinding the second ground portion (51). That is, it is possible to form the second cutting edge (30) into a desired shape during grinding of the first ground portion (50) and suppress a grind stone from interfering with the second cutting edge (30) during grinding of the second ground portion (51). Therefore, a radial rake angle of the second cutting edge (30) can be suppressed from becoming a large negative angle and thus cutting performance of the second cutting edge (30) can be enhanced.