In this article, we will be discussing the UNC and UNF Nut Dimensions in mm and inches. They follow the ISO standardization [ISO (the International Organization for Standardization)]. Let’s get right into it.
UNC and UNF Threads
The UNC Thread stands for Unified National Coarse Thread, comparable to the ISO metric thread, and the UNF thread stands for Unified National Fine Thread.
UNF and UNC are symbols for the Unified Screw Thread Series, standardized with gauge and determined based on the number of threads per inch. Compared to UNC threads, UNF threads are Unified fine-pitch threads. Both UNF and UNC thread screws are utilized for fastening; however, they are primarily employed in various industries.
Difference Between UNC and UNF Threads
UNF threads differ from UNC threads because they have fewer threads per unit of distance. Let’s see more differences between the two:
| UNC Thread | UNF Thread |
| The UNC thread is better suited to handling higher tensile and impact forces because it has fewer teeth of the same length and a bigger cross-section size for each tooth. | UNF threads are used when sealing is required because they have a narrower pitch and more teeth screwed into the same thread length. |
| A coarse screw thread is stronger and more interchangeable than a fine screw thread. | A fine screw thread is slightly weaker than a coarse thread. |
| UNC bolts’ coarse threads are adaptable, durable, and frequently used in general-purpose, lower-tolerance applications. | The UNF threads are better tight and have a lower helix angle. It is generally used for thin-walled parts and parts with higher anti-vibration requirements. |
| Greater tolerances, better production, and plating capabilities are all advantages of UNC threading over UNF threading. | With tolerances and production, UNC takes over UNF threads. |
Dimensions in mm and inches
I. UNC – Unified Coarse Threads
UNC threads according to ANSI B1.1:
| Major Diameter (inches) | Threads per inch (tpi) | Major Diameter (mm) | Major Diameter (inches) | Tap Drill Size (mm) | Pitch (mm) |
| #1 – 64 | 64 | 1.854 | 0.073 | 1.50 | 0.397 |
| #2 – 56 | 56 | 2.184 | 0.086 | 1.80 | 0.453 |
| #3 – 48 | 48 | 2.515 | 0.099 | 2.10 | 0.529 |
| #4 – 40 | 40 | 2.845 | 0.112 | 2.35 | 0.635 |
| #5 – 40 | 40 | 3.175 | 0.125 | 2.65 | 0.635 |
| #6 – 32 | 32 | 3.505 | 0.138 | 2.85 | 0.794 |
| #8 – 32 | 32 | 4.166 | 0.164 | 3.50 | 0.794 |
| #10 – 24 | 24 | 4.826 | 0.190 | 4.00 | 1.058 |
| #12 – 24 | 24 | 5.486 | 0.216 | 4.65 | 1.058 |
| 1/4″ – 20 | 20 | 6.350 | 0.250 | 5.35 | 1.270 |
| 5/16″ – 18 | 18 | 7.938 | 0.313 | 6.80 | 1.411 |
| 3/8″ – 16 | 16 | 9.525 | 0.375 | 8.25 | 1.587 |
| 7/16″ – 14 | 14 | 11.112 | 0.438 | 9.65 | 1.814 |
| 1/2″ – 13 | 13 | 12.700 | 0.500 | 11.15 | 1.954 |
| 9/16″ – 12 | 12 | 14.288 | 0.563 | 12.60 | 2.117 |
| 5/8″ – 11 | 11 | 15.875 | 0.625 | 14.05 | 2.309 |
| 3/4″ – 10 | 10 | 19.050 | 0.750 | 17.00 | 2.540 |
| 7/8″ – 9 | 9 | 22.225 | 0.875 | 20.00 | 2.822 |
| 1″ – 8 | 8 | 25.400 | 1.000 | 22.85 | 3.175 |
| 1 1/8″ – 7 | 7 | 28.575 | 1.125 | 25.65 | 3.628 |
| 1 1/4″ – 7 | 7 | 31.750 | 1.250 | 28.85 | 3.628 |
| 1 3/8″ – 6 | 6 | 34.925 | 1.375 | 31.55 | 4.233 |
| 1 1/2″ – 6 | 6 | 38.100 | 1.500 | 34.70 | 4.233 |
| 1 3/4″ – 5 | 5 | 44.450 | 1.750 | 40.40 | 5.080 |
| 2″ – 4 1/2 | 4 1/2 | 50.800 | 2.000 | 46.30 | 5.644 |
| 2 1/4″ – 4 1/2 | 4 1/2 | 57.150 | 2.250 | 52.65 | 5.644 |
| 2 1/2″ – 4 | 4 | 63.500 | 2.500 | 58.50 | 6.350 |
| 2 3/4″ – 4 | 4 | 69.850 | 2.750 | 64.75 | 6.350 |
| 3″ – 4 | 4 | 76.200 | 3.000 | 71.10 | 6.350 |
| 3 1/4″ – 4 | 4 | 82.550 | 3.250 | 77.45 | 6.350 |
| 3 1/2″ – 4 | 4 | 88.900 | 3.500 | 83.80 | 6.350 |
| 3 3/4″ – 4 | 4 | 95.250 | 3.750 | 90.15 | 6.350 |
| 4″ – 4 | 4 | 101.600 | 4.000 | 96.50 | 6.350 |
II. UNF – Unified National Fine Threads
UNF threads ANSI B1.1:
| Major Diameter (inches) | Threads per inch (tpi) | Major Diameter (mm) | Major Diameter (inches) | Tap Drill Size (mm) | Pitch (mm) |
| #0 – 80 | 80 | 1.524 | 0.060 | 1.25 | 0.317 |
| #1 – 72 | 72 | 1.854 | 0.073 | 1.55 | 0.353 |
| #2 – 64 | 64 | 2.184 | 0.086 | 1.90 | 0.397 |
| #3 – 56 | 56 | 2.515 | 0.099 | 2.15 | 0.453 |
| #4 – 48 | 48 | 2.845 | 0.112 | 2.40 | 0.529 |
| #5 – 44 | 44 | 3.175 | 0.125 | 2.70 | 0.577 |
| #6 – 40 | 40 | 3.505 | 0.138 | 2.95 | 0.635 |
| #8 – 36 | 36 | 4.166 | 0.164 | 3.50 | 0.705 |
| #10 – 32 | 32 | 4.826 | 0.190 | 4.10 | 0.794 |
| #12 – 28 | 28 | 5.486 | 0.216 | 4.70 | 0.907 |
| 1/4″ – 28 | 28 | 6.350 | 0.250 | 5.50 | 0.907 |
| 5/16″ – 24 | 24 | 7.938 | 0.313 | 6.90 | 1.058 |
| 3/8″ – 24 | 24 | 9.525 | 0.375 | 8.50 | 1.058 |
| 7/16″ – 20 | 20 | 11.112 | 0.438 | 9.90 | 1.270 |
| 1/2″ – 20 | 20 | 12.700 | 0.500 | 11.50 | 1.270 |
| 9/16″ – 18 | 18 | 14.288 | 0.563 | 12.90 | 1.411 |
| 5/8″ – 18 | 18 | 15.875 | 0.625 | 14.50 | 1.411 |
| 3/4″ – 16 | 16 | 19.050 | 0.750 | 17.50 | 1.587 |
| 7/8″ – 14 | 14 | 22.225 | 0.875 | 20.40 | 1.814 |
| 1″ – 12 | 12 | 25.400 | 1.000 | 23.25 | 2.117 |
| 1 1/8″ – 12 | 12 | 28.575 | 1.125 | 26.50 | 2.117 |
| 1 1/4″ – 12 | 12 | 31.750 | 1.250 | 29.50 | 2.117 |
| 1 3/8″ – 12 | 12 | 34.925 | 1.375 | 32.75 | 2.117 |
| 1 1/2″ – 12 | 12 | 38.100 | 1.500 | 36.00 | 2.117 |
