Introduction
Quick Answer: The UNC Thread Chart provides a quick reference for common Unified National Coarse (UNC) thread sizes and their basic dimensions.
The UNC Thread Chart provides a quick reference for common Unified National Coarse (UNC) 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 UNC threads.
UNC is the coarse-pitch series within the Unified Thread Standard (UTS) and is widely used for general-purpose mechanical fastening and industrial applications.
UNC 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) | ||
| #1 – 64 UNC | 64 | 0.073 | 1.854 | 0.0544 | 1.382 | 0.0085 | 0.216 |
| #2 – 56 UNC | 56 | 0.086 | 2.184 | 0.0647 | 1.643 | 0.0097 | 0.246 |
| #3 – 48 UNC | 48 | 0.099 | 2.515 | 0.0742 | 1.885 | 0.0113 | 0.287 |
| #4 – 40 UNC | 40 | 0.112 | 2.845 | 0.0822 | 2.088 | 0.0135 | 0.343 |
| #5 – 40 UNC | 40 | 0.125 | 3.175 | 0.0952 | 2.418 | 0.0135 | 0.343 |
| #6 – 32 UNC | 32 | 0.138 | 3.505 | 0.1008 | 2.56 | 0.0169 | 0.429 |
| #8 – 32 UNC | 32 | 0.164 | 4.166 | 0.1268 | 3.221 | 0.0169 | 0.429 |
| #10 – 24 UNC | 24 | 0.19 | 4.826 | 0.1404 | 3.566 | 0.0226 | 0.574 |
| #12 – 24 UNC | 24 | 0.216 | 5.486 | 0.1664 | 4.227 | 0.0226 | 0.574 |
| 1/4 – 20 UNC | 20 | 0.25 | 6.35 | 0.1905 | 4.839 | 0.0271 | 0.688 |
| 5/16 – 18 UNC | 18 | 0.313 | 7.938 | 0.2463 | 6.256 | 0.0301 | 0.765 |
| 3/8 – 16 UNC | 16 | 0.375 | 9.525 | 0.3006 | 7.635 | 0.0338 | 0.859 |
| 7/16 – 14 UNC | 14 | 0.438 | 11.112 | 0.3524 | 8.951 | 0.0387 | 0.983 |
| 1/2 – 13 UNC | 13 | 0.5 | 12.7 | 0.4084 | 10.373 | 0.0416 | 1.057 |
| 9/16 – 12 UNC | 12 | 0.563 | 14.288 | 0.4633 | 11.768 | 0.0451 | 1.146 |
| 5/8 – 11 UNC | 11 | 0.625 | 15.875 | 0.5167 | 13.124 | 0.0492 | 1.25 |
| 3/4 – 10 UNC | 10 | 0.75 | 19.05 | 0.6309 | 16.025 | 0.0541 | 1.374 |
| 7/8 – 9 UNC | 9 | 0.875 | 22.225 | 0.7427 | 18.865 | 0.0601 | 1.527 |
| 1 – 8 UNC | 8 | 1 | 25.4 | 0.8512 | 21.62 | 0.0677 | 1.72 |
| 1 1/8 – 7 UNC | 7 | 1.125 | 28.575 | 0.9549 | 24.254 | 0.0773 | 1.963 |
| 1 1/4 – 7 UNC | 7 | 1.25 | 31.75 | 1.0799 | 27.429 | 0.0773 | 1.963 |
| 1 3/8 – 6 UNC | 6 | 1.375 | 34.925 | 1.1766 | 29.886 | 0.0902 | 2.291 |
| 1 1/2 – 6 UNC | 6 | 1.5 | 38.1 | 1.3015 | 33.058 | 0.0902 | 2.291 |
| 1 3/4 – 5 UNC | 5 | 1.75 | 44.45 | 1.5118 | 38.4 | 0.1083 | 2.751 |
| 2 – 4.5 UNC | 4.5 | 2 | 50.8 | 1.7354 | 44.079 | 0.1203 | 3.056 |
| 2 1/4 – 4.5 UNC | 4.5 | 2.25 | 57.15 | 1.9523 | 49.588 | 0.1203 | 3.056 |
| 2 1/2 – 4 UNC | 4 | 2.5 | 63.5 | 2.2023 | 55.938 | 0.1353 | 3.437 |
| 2 3/4 – 4 UNC | 4 | 2.75 | 69.85 | 2.4523 | 62.288 | 0.1353 | 3.437 |
| 3 – 4 UNC | 4 | 3 | 76.2 | 2.7023 | 68.638 | 0.1353 | 3.437 |
| 3 1/4 – 4 UNC | 4 | 3.25 | 82.55 | 2.9523 | 74.988 | 0.1353 | 3.437 |
| 3 1/2 – 4 UNC | 4 | 3.5 | 88.9 | 3.2023 | 81.338 | 0.1353 | 3.437 |
| 3 3/4 – 4 UNC | 4 | 3.75 | 95.25 | 3.4523 | 87.688 | 0.1353 | 3.437 |
| 4 – 4 UNC | 4 | 4 | 101.6 | 3.7023 | 94.038 | 0.1353 | 3.437 |
Need More Information About UNC Threads?
The chart provides dimensional data, while the UNC Thread Guide explains the UNC thread system in greater detail, including designation, applications, thread classes, and differences between UNC and other Unified thread series.
How to Use the UNC Thread Chart
To identify or verify a UNC thread, compare the following parameters:
- Thread designation
- Nominal diameter
- Threads Per Inch (TPI)
- Thread pitch
- Major diameter
- Pitch diameter
- Minor diameter
For a specific thread size, the individual thread specification should also be reviewed for applicable tolerances and thread class.
Frequently Asked Questions
Q1: What is a UNC thread?
UNC stands for Unified National Coarse. It is the coarse-pitch series within the Unified Thread Standard and is commonly used for general-purpose fastening applications.
Q2: What does UNC mean on a thread designation?
UNC identifies the thread as belonging to the Unified National Coarse series. For example, 1/4-20 UNC indicates a 1/4-inch nominal diameter and 20 threads per inch.
Q3: What is TPI in a UNC thread chart?
TPI stands for Threads Per Inch and indicates the number of thread pitches contained within one inch.
Q4: What is the difference between UNC and UNF?
UNC uses a coarser pitch, while UNF uses a finer pitch for corresponding nominal diameters.
Q5: Can I identify a UNC thread using this chart?
A UNC chart can help identify a thread when its approximate diameter and TPI are known. For reliable identification, the thread standard and complete designation should also be verified.
Related Thread Resources
- UNC Thread Guide
- UNF Thread Chart
- UNEF Thread Chart
- Thread Definitions
- Metric Coarse Threads Chart
- Metric Fine Threads Chart
- Thread Standards
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
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