Thread Mill With Inverted Spiral Flutes for Burr Reduction
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Solution Overview
Problem
Conventional thread mills often leave burrs in the chamfered portion of internal threads due to negative rake angles on cutting edges, which can impede thread engagement and require additional chamfering steps.
Innovation Solution
A thread mill design with spiral flutes that twist in a direction opposite to the rotating direction, providing a positive rake angle, and annular protrusions configured to cut the entirety of each thread ridge, including its crest, to minimize burr formation and enhance cutting sharpness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional thread mills with right-hand spiral flutes are used, then chips are evacuated toward the shank, but negative rake angles are created on rear flanks causing burr formation
Solution Approach 1:
The patent inverts the conventional flute twist direction by using left-hand spiral flutes instead of right-hand flutes. This reversal changes the chip evacuation direction and creates positive rake angles on the rear flanks, eliminating burr formation while maintaining effective cutting performance.
Solution Approach 2:
The patent changes the helix angle parameter of the flutes from conventional right-hand configurations to left-hand configurations with specific helix angles (15-30 degrees). This parameter change transforms the rake angle from negative to positive, fundamentally improving cutting performance and eliminating burrs.
2Ease of operation
If flutes twist in the same direction as rotating direction, then chip evacuation is achieved, but cutting edges cannot exhibit satisfactory cutting performance
Solution Approach 1:
The patent reverses the relationship between flute twist direction and rotation direction. Instead of flutes twisting in the same direction as rotation (conventional), the flutes twist in the opposite direction, creating positive rake angles that enable satisfactory cutting performance without burr formation.
3Manufacturing precision
If additional chamfering steps are performed to remove burrs, then thread accuracy is improved, but manufacturing time increases
Solution Approach 1:
The thread mill design makes the tool self-sufficient by incorporating left-hand spiral flutes that prevent burr formation during the primary threading operation. This eliminates the need for secondary chamfering operations to remove burrs, as the tool itself prevents the problem from occurring in the first place.
Solution Approach 2:
The patent enables continuous threading operation without interruption for burr removal. By preventing burr formation during the main cutting process through the inverted flute configuration, the useful action of thread formation continues uninterrupted, eliminating wasted time on corrective chamfering operations.
Data Source
AI summary
A thread mill that is to be moved along a helical interpolation path while being rotated about an axis of the thread mill in a rotating direction, for forming a thread in a circumferential surface of a workpiece. The thread mill includes a cylindrical main body having (a) at least one spiral flute formed in an outer circumferential surface of the cylindrical main body, and (b) at least one cutting edge each provided by a rear-side one of widthwise opposite edges, as viewed in the rotating direction, of a corresponding one of the at least one spiral flute. Each of the at least one spiral flute extends in a direction opposite to the rotating direction as viewed in a direction away from a proximal end of the cylindrical main body toward a distal end of the cylindrical main body. Also disclosed is a method of forming the thread by using the thread mill.