Quick Definition
Quick Answer: Thread Angle is the included angle formed between the two flanks of a screw thread.
Thread Angle is the included angle formed between the two flanks of a screw thread. Different thread standards specify different thread angles depending on their intended applications.
What Is Thread Angle?
Thread Angle defines the shape of the thread profile by measuring the angle between the two opposing thread flanks.
It is one of the fundamental geometric characteristics of screw threads and influences strength, load distribution, friction, and manufacturing.
Different thread standards adopt different Thread Angles to optimize performance for specific applications.
For example:
- Unified (UNC/UNF): 60°
- ISO Metric: 60°
- Whitworth (BSW): 55°
- ACME Threads: 29°
Why Is Thread Angle Important?
Thread Angle affects how forces are transmitted between mating threads.
It also influences:
- Load distribution
- Friction during assembly
- Wear resistance
- Manufacturing methods
- Thread compatibility
Two threads with the same diameter and pitch but different Thread Angles are generally not interchangeable.
How Is Thread Angle Measured?
Method 1 – Optical Comparator
A common method for precision inspection of thread profiles.
Method 2 – Profile Projector
Used in manufacturing and quality control laboratories.
Method 3 – Coordinate Measuring Machine (CMM)
Provides highly accurate geometric measurements for precision applications.
Common Thread Angles
| Thread Standard | Thread Angle |
| ISO Metric | 60° |
| UNC / UNF | 60° |
| Whitworth (BSW) | 55° |
| ACME | 29° |
Frequently Asked Questions
- What is the standard Thread Angle for Metric threads?
ISO Metric threads use a 60° thread angle.
- Do UNC and Metric threads have the same Thread Angle?
Yes. Both use a 60° included angle, although their dimensions and pitch systems differ.
- Can different Thread Angles be mixed?
No. Threads with different angles are generally incompatible.
- Why is Thread Angle important?
It affects thread strength, fit, wear characteristics, and overall performance.
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