Spiral Flute Tap with Variable Helix Angle for Chip Evacuation
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Solution Overview
Problem
Conventional spiral flute taps face challenges with bird nesting or chip wrap, especially in deep hole tapping and long chipping materials, due to limited chip lifting force and mechanical strength, which existing taps fail to adequately address.
Innovation Solution
A spiral flute tap design featuring a variable helix geometry with a slow-to-fast flute helix change from the axial forward end to the rearward end, where the helix angle continuously increases, thereby reducing the lead and minimizing bird nesting and chip wrap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high helix angle flute is used for chip evacuation, then chip lifting force is improved, but bird nesting or chip wrap occurs
Solution Approach 1:
The patent applies a dynamically varying helix angle along the axial length of the tap. The helix angle transitions from a lower angle (15-30 degrees) at the leading end to a higher angle (30-45 degrees) at the trailing end. This dynamic geometric variation allows the tap to adapt its chip evacuation capability and mechanical strength characteristics along its length, resolving the contradiction between chip lifting force and bird nesting prevention.
Solution Approach 2:
Different sections of the tap flute have different helix angles optimized for their specific functions. The leading end with lower helix angle provides mechanical strength and controlled chip formation, while the trailing end with higher helix angle provides enhanced chip evacuation. This local differentiation of geometric properties eliminates the need to compromise either chip lifting or bird nesting across the entire tap length.
2Strength
If a low helix angle flute is used for mechanical strength, then mechanical strength is improved, but chip lifting force is limited
Solution Approach 1:
The helix angle is dynamically varied along the axial direction, transitioning from lower (15-30 degrees) at the leading end for mechanical strength to higher (30-45 degrees) at the trailing end for chip evacuation. This dynamic geometry allows both strength and chip lifting requirements to be satisfied at different locations.
Solution Approach 2:
The leading end of the tap features a lower helix angle optimized for mechanical strength and controlled cutting, while the trailing end features a higher helix angle optimized for chip evacuation. This local optimization of geometric properties resolves the contradiction between strength and chip lifting force.
3Productivity
If a fast spiral flute helix angle is used for chip evacuation, then chip lifting force is improved, but bird nesting or chip wrap occurs in long chipping materials
Solution Approach 1:
The patent implements a dynamic helix angle progression along the axial length, starting with lower angles (15-30 degrees) at the leading end to prevent bird nesting in long chips, and transitioning to higher angles (30-45 degrees) at the trailing end to provide effective chip evacuation. This dynamic variation resolves the contradiction for long chipping materials.
Solution Approach 2:
The leading end with lower helix angle prevents bird nesting by providing mechanical strength and controlled chip formation, while the trailing end with higher helix angle provides the chip evacuation capability needed for long chips. This local differentiation resolves the contradiction specific to long chipping materials.
Data Source
AI summary
A spiral flute tap includes a body having an axial forward end and an axial rearward end. The body has a cylindrical shank portion adjacent the axial rearward end, a threaded fluted portion adjacent the axial forward end, a non-threaded fluted portion between the cylindrical shank portion and the threaded fluted portion, and a central, longitudinal axis. The spiral flute tap further includes a plurality of helical flutes formed at a helix angle, HA, with respect to the central, longitudinal axis of the tap that continuously increases in magnitude in the threaded fluted portion. In other words, the lead of the plurality of helical flutes continuously decreases in magnitude in a rearward direction for a predetermined distance. In one example, the helix angle, HA, varies at a rate of between 0.5 degrees/mm to 4.0 degrees/mm. A method of making the spiral flute tap is also disclosed.