Introduction
Quick Answer: The UNEF Thread Chart provides a quick reference for common Unified National Extra Fine (UNEF) thread sizes and their basic dimensions.
The UNEF Thread Chart provides a quick reference for common Unified National Extra Fine (UNEF) thread sizes and their basic dimensions.
Use this chart to quickly find Threads Per Inch (TPI), thread pitch, major diameter, pitch diameter, minor diameter,and other basic thread dimensions for UNEF threads.
UNEF threads use a finer pitch than the corresponding UNC and UNF series and are generally used for specialized applications where an extra-fine thread is appropriate.
UNEF Thread Chart
Click Thread Link to check more data for each thread.
| Thread | Threads per inch (TPI) | Basic Major Diameter | Basic Minor Diameter | Thread Height | |||
| (in) | (mm) | (in) | (mm) | (in) | (mm) | ||
| #12 – 32 UNEF | 32 | 0.216 | 5.486 | 0.1788 | 4.542 | 0.0169 | 0.429 |
| 1/4 – 32 UNEF | 32 | 0.25 | 6.35 | 0.2128 | 5.405 | 0.0169 | 0.429 |
| 5/16 – 32 UNEF | 32 | 0.3125 | 7.938 | 0.2753 | 6.993 | 0.0169 | 0.429 |
| 3/8 – 32 UNEF | 32 | 0.375 | 9.525 | 0.3378 | 8.58 | 0.0169 | 0.429 |
| 7/16 – 28 UNEF | 28 | 0.4375 | 11.113 | 0.3949 | 10.03 | 0.0193 | 0.49 |
| 1/2 – 28 UNEF | 28 | 0.5 | 12.7 | 0.4574 | 11.618 | 0.0193 | 0.49 |
| 9/16 – 24 UNEF | 24 | 0.5625 | 14.288 | 0.5129 | 13.028 | 0.0226 | 0.574 |
| 5/8 – 24 UNEF | 24 | 0.625 | 15.875 | 0.5754 | 14.615 | 0.0226 | 0.574 |
| 11/16 – 24 UNEF | 24 | 0.6875 | 17.463 | 0.6379 | 16.203 | 0.0226 | 0.574 |
| 3/4 – 20 UNEF | 20 | 0.75 | 19.05 | 0.6905 | 17.539 | 0.0271 | 0.688 |
| 13/16 – 20 UNEF | 20 | 0.8125 | 20.638 | 0.753 | 19.126 | 0.0271 | 0.688 |
| 7/8 – 20 UNEF | 20 | 0.875 | 22.225 | 0.8155 | 20.714 | 0.0271 | 0.688 |
| 15/16 – 20 UNEF | 20 | 0.9375 | 23.813 | 0.878 | 22.301 | 0.0271 | 0.688 |
| 1 – 20 UNEF | 20 | 1 | 25.4 | 0.9405 | 23.889 | 0.0271 | 0.688 |
| 1 1/16 – 18 UNEF | 18 | 1.0625 | 26.988 | 0.9964 | 25.309 | 0.0301 | 0.765 |
| 1 1/8 – 18 UNEF | 18 | 1.125 | 28.575 | 1.0589 | 26.896 | 0.0301 | 0.765 |
| 1 3/16 – 18 UNEF | 18 | 1.1875 | 30.163 | 1.1214 | 28.484 | 0.0301 | 0.765 |
| 1 1/4 – 18 UNEF | 18 | 1.25 | 31.75 | 1.1839 | 30.071 | 0.0301 | 0.765 |
| 1 5/16 – 18 UNEF | 18 | 1.3125 | 33.338 | 1.2464 | 31.659 | 0.0301 | 0.765 |
| 1 3/8 – 18 UNEF | 18 | 1.375 | 34.925 | 1.3089 | 33.246 | 0.0301 | 0.765 |
| 1 7/16 – 18 UNEF | 18 | 1.4375 | 36.513 | 1.3714 | 34.834 | 0.0301 | 0.765 |
| 1 1/2 – 18 UNEF | 18 | 1.5 | 38.1 | 1.4339 | 36.421 | 0.0301 | 0.765 |
| 1 9/16 – 18 UNEF | 18 | 1.5625 | 39.688 | 1.4964 | 38.009 | 0.0301 | 0.765 |
| 1 5/8 – 18 UNEF | 18 | 1.625 | 41.275 | 1.5589 | 39.596 | 0.0301 | 0.765 |
| 1 11/16 – 18 UNEF | 18 | 1.6875 | 42.863 | 1.6214 | 41.184 | 0.0301 | 0.765 |
Need More Information About UNEF Threads?
The UNEF Thread Guide provides additional information about the Unified National Extra Fine thread series, including its designation, applications, and relationship to UNC and UNF threads.
How to Use the UNEF Thread Chart
Use the chart to compare:
- Thread designation
- Nominal diameter
- Threads Per Inch (TPI)
- Thread pitch
- Major diameter
- Pitch diameter
- Minor diameter
When selecting or manufacturing a UNEF thread, the applicable thread class and tolerance should also be verified.
Frequently Asked Questions
Q1: What is a UNEF thread?
UNEF stands for Unified National Extra Fine. It is an extra-fine-pitch series within the Unified Thread Standard.
Q2: What is the difference between UNC, UNF, and UNEF?
They are different pitch series within the Unified Thread Standard. UNC uses coarse pitches, UNF uses fine pitches, and UNEF uses extra-fine pitches.
Q3: What does TPI mean in a UNEF chart?
TPI means Threads Per Inch and indicates how many thread pitches occur within one inch.
Q4: When are UNEF threads used?
UNEF threads are generally used in specialized applications where an extra-fine pitch is appropriate. The actual thread series should be selected according to the engineering requirements of the application.
Q5: Can UNEF replace UNF?
Not automatically. The diameter, pitch, thread class, mating component, and application requirements must all be verified before substitution.
Related Thread Resources
- UNEF Thread Guide
- UNC Thread Chart
- UNF Thread Chart
- Thread Definitions
- Metric Coarse Threads Chart
- Metric Fine Threads Chart
- Thread Standards
- Thread in EMI Filters
- Thread in Feedthrough Capacitors
LCA Thread Charts
The LCA Thread Charts are designed as a practical engineering reference for quickly locating common thread dimensions and comparing standardized thread sizes.
Use the chart that matches your thread system, or explore the individual Thread Specifications and Thread Engineering Guides when more detailed information is required.
Thread Definitions → Thread Standards → Thread Charts → Thread Specifications → Thread Engineering Guides
Engineering Support CTA: Selecting a threaded EMI filter or feedthrough capacitor? Share the thread standard and size, panel thickness, voltage/current, capacitance, and environmental requirements with LCA engineers. View Thread Mount Feedthrough Filters
