Introduction
Quick Answer: The UNF Thread Chart provides a quick reference for common Unified National Fine (UNF) thread sizes and their basic dimensions.
The UNF Thread Chart provides a quick reference for common Unified National Fine (UNF) 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 UNF threads.
UNF is the fine-pitch series within the Unified Thread Standard (UTS) and is commonly used where a finer thread pitch is required for a particular mechanical application.
UNF 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) | ||
| #0 – 80 UNF | 80 | 0.06 | 1.524 | 0.0451 | 1.146 | 0.0068 | 0.173 |
| #1 – 72 UNF | 72 | 0.073 | 1.854 | 0.0565 | 1.435 | 0.0075 | 0.191 |
| #2 – 64 UNF | 64 | 0.086 | 2.184 | 0.0674 | 1.712 | 0.0085 | 0.216 |
| #3 – 56 UNF | 56 | 0.099 | 2.515 | 0.0777 | 1.974 | 0.0097 | 0.246 |
| #4 – 48 UNF | 48 | 0.112 | 2.845 | 0.0872 | 2.215 | 0.0113 | 0.287 |
| #5 – 44 UNF | 44 | 0.125 | 3.175 | 0.0979 | 2.487 | 0.0123 | 0.312 |
| #6 – 40 UNF | 40 | 0.138 | 3.505 | 0.1082 | 2.748 | 0.0135 | 0.343 |
| #8 – 36 UNF | 36 | 0.164 | 4.166 | 0.1309 | 3.325 | 0.015 | 0.381 |
| #10 – 32 UNF | 32 | 0.19 | 4.826 | 0.1528 | 3.881 | 0.0169 | 0.429 |
| #12 – 28 UNF | 28 | 0.216 | 5.486 | 0.1735 | 4.407 | 0.0193 | 0.49 |
| 1/4 – 28 UNF | 28 | 0.25 | 6.35 | 0.2075 | 5.271 | 0.0193 | 0.49 |
| 5/16 – 24 UNF | 24 | 0.313 | 7.938 | 0.2629 | 6.678 | 0.0226 | 0.574 |
| 3/8 – 24 UNF | 24 | 0.375 | 9.525 | 0.3254 | 8.265 | 0.0226 | 0.574 |
| 7/16 – 20 UNF | 20 | 0.438 | 11.112 | 0.378 | 9.601 | 0.0271 | 0.688 |
| 1/2 – 20 UNF | 20 | 0.5 | 12.7 | 0.4405 | 11.189 | 0.0271 | 0.688 |
| 9/16 – 18 UNF | 18 | 0.563 | 14.288 | 0.4963 | 12.606 | 0.0301 | 0.765 |
| 5/8 – 18 UNF | 18 | 0.625 | 15.875 | 0.5588 | 14.194 | 0.0301 | 0.765 |
| 3/4 – 16 UNF | 16 | 0.75 | 19.05 | 0.6756 | 17.16 | 0.0338 | 0.859 |
| 7/8 – 14 UNF | 14 | 0.875 | 22.225 | 0.7899 | 20.063 | 0.0387 | 0.983 |
| 1 – 12 UNF | 12 | 1 | 25.4 | 0.9008 | 22.88 | 0.0451 | 1.146 |
| 1 1/8 – 12 UNF | 12 | 1.125 | 28.575 | 1.0258 | 26.055 | 0.0451 | 1.146 |
| 1 1/4 – 12 UNF | 12 | 1.25 | 31.75 | 1.1508 | 29.23 | 0.0451 | 1.146 |
| 1 3/8 – 12 UNF | 12 | 1.375 | 34.925 | 1.2758 | 32.405 | 0.0451 | 1.146 |
| 1 1/2 – 12 UNF | 12 | 1.5 | 38.1 | 1.4008 | 35.58 | 0.0451 | 1.146 |
Need More Information About UNF Threads?
The UNF Thread Guide provides a more detailed explanation of the Unified National Fine thread system, including its designation, typical applications, thread classes, and comparison with UNC and UNEF.
How to Use the UNF Thread Chart
To identify or verify a UNF thread, compare:
- Thread designation
- Nominal diameter
- Threads Per Inch (TPI)
- Thread pitch
- Major diameter
- Pitch diameter
- Minor diameter
The individual thread class and tolerance should be verified when determining actual mating or manufacturing requirements.
Frequently Asked Questions
Q1: What is a UNF thread?
UNF stands for Unified National Fine. It is the fine-pitch series within the Unified Thread Standard.
Q2: What does UNF mean on a thread designation?
UNF identifies the thread as a Unified National Fine thread. For example, 1/4-28 UNF indicates a 1/4-inch nominal diameter with 28 threads per inch.
Q3: What is the difference between UNC and UNF?
UNC uses a coarser pitch, while UNF uses a finer pitch for corresponding nominal diameters.
Q4: How is UNF pitch specified?
UNF threads are normally specified using Threads Per Inch (TPI). Pitch in millimeters can also be calculated from TPI when required.
Q5: Can I use a UNF chart to select a mating thread?
The chart can provide basic dimensional reference, but mating compatibility should also be verified using the complete designation, thread class, tolerance, and internal/external thread configuration.
Related Thread Resources
- UNF Thread Guide
- UNC 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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