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UNF Thread Pitch Chart
The UNF Thread Chart provided above is a quick reference guide for Unified National Fine thread sizes. Whether you're an engineer, machinist, maintenance technician, manufacturer, apprentice or workshop professional, this chart is designed to help you quickly identify the correct thread specifications for your project.
| Diameter | TPI | Drill Size (mm) |
|---|---|---|
| No. 0 | 80 | 1.25 mm |
| No. 1 | 72 | 1.55 mm |
| No. 2 | 64 | 1.9 mm |
| No. 3 | 56 | 2.15 mm |
| No. 4 | 48 | 2.4 mm |
| No. 5 | 44 | 2.7 mm |
| No. 6 | 40 | 2.95 mm |
| No. 8 | 36 | 3.5 mm |
| No. 10 | 32 | 4.1 mm |
| No. 12 | 28 | 4.7 mm |
| 1/4" | 28 | 5.5 mm |
| 5/16" | 24 | 6.9 mm |
| 3/8" | 24 | 8.5 mm |
| 7/16" | 20 | 9.9 mm |
| 1/2" | 20 | 11.5 mm |
| 9/16" | 18 | 12.9 mm |
| 5/8" | 18 | 14.5 mm |
| 3/4" | 16 | 17.50 mm |
| 7/8" | 14 | 20.4 mm |
| 1" | 12 | 23.25 mm |
| 1-1/8" | 12 | 26.5 mm |
| 1-1/4" | 12 | 29.5 mm |
| 1-3/8" | 12 | 32.75 mm |
| 1-1/2" | 12 | 36.00 mm |
What is a UNF Thread?
UNF stands for Unified National Fine, and it is part of the broader Unified Thread Standard (UTS). UNF threads feature a 60° thread profile and are characterised by a finer thread pitch compared to their UNC (Unified National Coarse) counterparts.
The finer pitch of UNF threads delivers several advantages: greater clamping force, improved resistance to vibration, and more precise adjustment capabilities. These qualities make UNF threads the preferred choice in demanding applications where precision and reliability are essential.
UNF threads are commonly found in automotive, aerospace, manufacturing, machinery and precision engineering applications where exacting standards are required.
How to Read the UNF Thread Chart
The chart above displays key information for each UNF thread size:
- Diameter — The nominal thread size, ranging from No. 0 through 1-1/2"
- TPI (Threads Per Inch) — The number of threads per inch, which defines the thread pitch
- Drill Size (mm) — The recommended tap drill size in millimetres for creating the threaded hole
Use these dimensions when selecting UNF taps, dies and drill bits for your machining or assembly work.
Common Applications
UNF threads are widely used across multiple industries:
- Automotive engineering and assembly
- Aerospace and aviation components
- Manufacturing and industrial machinery
- Precision engineering and instrumentation
- Hydraulic systems and fluid power
- Mechanical assemblies requiring vibration resistance
The superior holding power and vibration resistance of UNF threads make them ideal for critical fastening applications in these fields.
Frequently Asked Questions
What does UNF stand for?
UNF stands for Unified National Fine. It is a standardised thread form that is part of the Unified Thread Standard (UTS).
What is the difference between UNC and UNF?
UNC (Unified National Coarse) has a coarser pitch with fewer threads per inch, while UNF (Unified National Fine) has a finer pitch with more threads per inch. UNF threads provide greater clamping force and better vibration resistance, making them suitable for precision applications.
When should I use UNF threads?
Use UNF threads when you need superior holding power, improved vibration resistance, or more precise adjustment. They are ideal for automotive, aerospace and precision engineering applications.
Are UNF threads compatible with metric threads?
No, UNF threads are not directly compatible with metric threads. UNF uses imperial measurements and a 60° thread profile, while metric threads follow a different standard. Always verify thread compatibility before assembly.
Browse True Tooling's range of premium UNF taps, dies and drill bits for quality tooling trusted by Australian engineers and machinists.