Tap Thread Geometry for Burr and Cutting Edge Chipping Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional tapping processes using incomplete threads often result in burr generation around threaded holes due to chip engagement, leading to chipping of cutting edges when chips are discharged, especially when cutting edges are not chamfered.
Innovation Solution
A tap design with an incomplete thread and a complete thread, where the root diameter is greater than or equal to the nominal diameter minus the pitch, and the thread ridge height is less than or equal to half the pitch, with chamfered cutting edges at second and subsequent thread ridges to prevent chip engagement and chipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If cutting is performed by an entire incomplete thread, then burr generation is suppressed, but chips become longer and curl diameter becomes larger causing cutting edge chipping
Solution Approach 1:
The patent applies local quality by differentiating the root part geometry from the rest of the thread. Specifically, the root part (groove bottom) is designed with a larger radius of curvature than conventional taps, creating a locally modified geometry that enables cutting action in the root area without affecting the overall thread structure. This localized geometric modification allows the incomplete thread to cut effectively in the root part while maintaining appropriate chip discharge characteristics elsewhere.
Solution Approach 2:
The patent changes geometric parameters of the tap, specifically the radius of curvature at the groove bottom of the root part. By increasing this radius parameter, the tap geometry is modified to enable cutting action in the root area during incomplete threading. This parameter change transforms the non-cutting root part into an active cutting region, suppressing burr generation while controlling chip formation through the modified geometry.
2Reliability
If chamfered cutting edges are applied to second and subsequent thread ridges, then chip engagement and chipping are prevented, but manufacturing complexity increases
Solution Approach 1:
The chamfered cutting edges are applied selectively to the second and subsequent thread ridges rather than uniformly across all ridges. This local quality approach means that only specific portions of the tap (the cutting edges on ridges 2 and beyond) receive the chamfer treatment, while the first ridge maintains its original geometry. This selective application reduces the overall manufacturing complexity compared to chamfering all ridges, while still providing the protective function where it is most needed.
Data Source
AI summary
A tap including an incomplete thread having a plurality of thread ridges that threads a workpiece, a complete thread including a cutting edge formed continuously from the incomplete thread, and a groove part that is disposed in each of the incomplete thread and the complete thread to discharge chips of the workpiece, wherein relationships respectively expressed by Equation (1): D1≥D0−P and Equation (2): h≤P/2 are simultaneously satisfied in a relationship among a nominal diameter D0 of the tap 100, a root diameter D1, a pitch P, and a thread ridge height h.