Coupling Mechanism for Cutting Tool with Conical Mating Surfaces
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Solution Overview
Problem
Current coupling mechanisms for rotary cutting tools face challenges with high production tolerances and material stress issues, leading to costly waste and potential connection failure when using sintered carbide cutters with steel shanks, particularly due to restrictive cylindrical mating surfaces and uneven stress distribution during threading.
Innovation Solution
The solution involves a modular design with a male threaded portion on the cutter and a female threaded portion on the shank, where the thread pitches differ by up to 0.010 mm and the threads are oriented at varying angles, dispersing stress evenly and allowing for accurate alignment without additional grinding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cylindrical mating surfaces with tight tolerances (less than 5 micrometers) are used for coupling the cutter to the shank, then accurate centering and positioning of the cutter on the spindle axis is achieved, but production complexity increases due to the need for additional grinding processes
Solution Approach 1:
The patent changes the geometric parameters of the coupling mechanism by using conical mating surfaces instead of cylindrical ones. The conical surfaces with specific taper angles provide the necessary alignment and positioning accuracy without requiring tight tolerance grinding processes, thus resolving the contradiction between manufacturing precision and ease of manufacture.
Solution Approach 2:
Instead of using cylindrical surfaces that require tight tolerances for accurate positioning, the patent inverts the approach by using conical surfaces where the geometry itself provides the alignment function. The conical shape inherently guides the cutter to the correct position and orientation, eliminating the need for additional grinding processes.
2Strength
If a carbide cutter is directly threaded into a steel shank, then the coupling strength is sufficient for operation, but stress concentration occurs at the base of the threaded portion leading to connection failure and shank damage
Solution Approach 1:
The patent introduces an intermediary coupling mechanism with conical mating surfaces that mediates between the carbide cutter and steel shank. This intermediary structure distributes the threading stresses more evenly across the coupling interface, preventing stress concentration at the thread base and eliminating the risk of connection failure and shank damage.
Solution Approach 2:
The conical coupling surfaces provide a stress-distributing interface before the threading engagement occurs. The geometry of the conical surfaces is designed to cushion and distribute the insertion and operational stresses, preventing the concentration of forces that would lead to connection failure.
3Ease of manufacture
If the same thread pitch is used for both the male threaded portion on the cutter and the female threaded portion on the shank, then the threading process is simple, but stress is unevenly distributed during engagement
Solution Approach 1:
The patent applies different thread pitches to the male and female threaded portions, creating local variation in the threading geometry. This local differentiation allows for more uniform stress distribution during engagement, with the different pitches working together to distribute forces evenly across the coupling interface.
Data Source
AI summary
A rotary cutting tool includes a cutter of generally cylindrical shape disposed about a central longitudinal axis. The cutter has a first end having an active fluted portion and an opposite second end, the second end having a male threaded portion disposed thereabout. The cutting tool further includes a shank of generally cylindrical shape disposed about the central longitudinal axis, the shank having a recessed female threaded portion formed in a first end. The male threaded portion includes a number of threads disposed at a first pitch and the female threaded portion includes a number of threads disposed at a second pitch different than the first pitch. The cutter and the shank are selectively coupled via threaded engagement of the male threaded portion and the female threaded portion.