Three-flute drill concave cutting edge chip curling
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Solution Overview
Problem
Conventional three-flute drills experience insufficient chip discharge and durability issues due to longer needle-like chip projections, leading to clogging and cracking, particularly with smaller flute widths and cross-sectional areas.
Innovation Solution
The three-flute drill design features a concave amount of the first concave curve within 0.01D to 0.05D, a rake chamfer width of 0.005D to 0.06D, and a web thickness of 0.15D to 0.50D, along with specific curvature radii and rake angles, to curl and break chips into shorter pieces, enhancing discharge performance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a three-flute drill with conventional straight cutting edges is used, then the chip discharge property is insufficient due to longer needle-like chip projections, but the flute width and cross-sectional area are already limited by the three-flute configuration
Solution Approach 1:
The cutting edge is designed with a concave curve having a specific curvature radius (0.04D to 0.09D) to curl chips into a C-shape or spiral form. This curvature transforms the chip morphology from long needle-like projections to compact curled shapes that occupy less space and discharge more easily through the limited flute width and cross-sectional area of the three-flute drill.
2Productivity
If the flute width is reduced to accommodate three flutes, then chip discharge becomes more difficult, but drill strength must be maintained
Solution Approach 1:
The drill design optimizes multiple parameters simultaneously: the concave curve curvature radius (0.04D to 0.09D) controls chip curling, the web thickness (0.15D to 0.50D) maintains structural strength, and the rake angle (0° to 15°) influences chip flow. These parameter changes work together to achieve effective chip discharge while preserving drill strength and rigidity.
3Shape
If conventional cutting edges are used, then chip curling is insufficient and needle-like projections form, but the drill structure is simpler
Solution Approach 1:
The cutting edge incorporates a concave curve with a specifically controlled curvature radius (0.04D to 0.09D) that actively curls chips during cutting. This geometric modification transforms chip morphology from straight needle-like projections to compact C-shaped or spiral curls, significantly improving chip discharge performance despite the increased geometric complexity of the cutting edge.
4Ease of operation
If the concave amount of the first concave curve is increased to improve chip curling, then chip discharge improves, but the outer circumferential corner portion of the cutting edge may crack
Solution Approach 1:
The design precisely controls the concave amount LF within the range of 0.01D to 0.05D and the curvature radius within 0.04D to 0.09D. These parameter boundaries ensure sufficient chip curling and discharge performance while preventing excessive stress concentration that would cause cracking at the outer circumferential corner portion of the cutting edge, thereby maintaining both chip discharge performance and cutting edge durability.
Data Source
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AI summary
Each cutting blade (12) has an outer peripheral side cutting blade portion (12a) shaped like a convex curve and an inner peripheral side cutting blade portion (12b) shaped like a concave curve. On the cross section perpendicular to the axis, the first convex curve (CL1) corresponding to the convex curve shaped cutting blade portion (12a) crosses the first concave curve (CL2) corresponding to the concave curve shaped cutting blade portion (12b) at a cross point (A). Therefore, the range of the first convex curve (CL1) can be reduced and the first concave curve (CL2) can be enlarged to the outer peripheral side, and the concavity amount (LF) of the first concave curve (CL2) can be increased. As a result, the generated chips are curled appropriately and become easy to break in the first concave curve (CL2) portion of a chip discharge groove (18). Since the chips have relatively short curl shape free of needle-shaped bumps, the chips can be discharged smoothly so that the chip discharge performance can be improved. For the 3-blade drill (10) with the chip discharge groove (18) having relatively small groove width and cross-sectional area, jamming caused by chips can be restrained, and the service life of the tool can be further improved.