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Threaded rod, inch: #4 to 4 in, UNC and UNF threads per inch, major diameter in inches and mm, standard lengths
What are the threads per inch and diameter of 1/4, 3/8, 1/2 and 5/8 inch threaded rod? · Standard part · basis: ASME B18.31.3 as summarised by Torqbolt (sizes, TPI) and fasten.it (lengths); numbers only
Also called: 1/4 20 threaded rod diameter, 3/8-16 threaded rod, 1/2-13 all thread, 5/8-11 threaded rod, threaded rod sizes inch, all thread tpi chart, threaded rod standard lengths, threaded rod pitch inch, 1/4-28 vs 1/4-20 rod, unc threads per inch chart, all thread rod diameter mm, 3/4-10 threaded rod, 7/16 14 threaded rod, 1/2 inch threaded rod mm
Exact dimensions. Every file is drawn at true size with no tolerance added. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your process's clearance before making the part. Mating features
- sizes
- 30 in table
Notes
- Inch threaded rod (studding, all-thread; ASME B18.31.3) is cut from stock in the UNC (coarse) or UNF (fine) series. Sizes and threads per inch are from Torqbolt's B18.31.3 summary. Its 7/16 row prints 0.4370 in; the fraction 7/16 is 0.4375 in and that is shown. The second source's table (fasten.it) lists the UNC and UNF numbers one row out of step for the fractional sizes (its UNC column reads 18 for 1/4 where Torqbolt has 20, and 16 for 5/16 where Torqbolt has 18), so its TPI numbers are not used.
- Nominal diameter is the major diameter of the thread; the major diameter limits that the standard prints were not on a page that could be read. No file is added: a rod is a plain cylinder (Xem draws threads as plain cylinders at the major diameter) and carries no more than the number.
- Lengths: ASME B18.31.3 says rods are normally produced in, but not limited to, 3 ft, 6 ft, 10 ft and 12 ft; length tolerance is ±1/2 in for nominal lengths of 6 ft and longer and ±1/4 in under 6 ft (fasten.it's B18.31.3 page). Cut-to-length rods are common.
- Metric rod (DIN 976, M3 to M12) is on the threaded-rod-metric-din-976 page. Left out: thread class limits, minor and pitch diameters, mechanical grades (A307, B7, 18-8) and the UNS-size 1-14 for 1 in UNF.
Threaded rod, inch: #4 to 4 in, UNC and UNF threads per inch, major… size chart
| size | nominal major diameter (in) | major diameter (mm, computed) | UNC | UNC pitch (mm, computed 25.4 ÷ TPI) | UNF |
|---|---|---|---|---|---|
| #4 | 0.1120 | 2.84 | 4-40 | 0.635 | 4-48 |
| #5 | 0.1250 | 3.17 | 5-40 | 0.635 | 5-44 |
| #6 | 0.1380 | 3.51 | 6-32 | 0.794 | 6-40 |
| #8 | 0.1640 | 4.17 | 8-32 | 0.794 | 8-36 |
| #10 | 0.1900 | 4.83 | 10-24 | 1.058 | 10-32 |
| #12 | 0.2160 | 5.49 | 12-24 | 1.058 | 12-28 |
| 1/4 | 0.2500 | 6.35 | 1/4-20 | 1.270 | 1/4-28 |
| 5/16 | 0.3125 | 7.94 | 5/16-18 | 1.411 | 5/16-24 |
| 3/8 | 0.3750 | 9.52 | 3/8-16 | 1.587 | 3/8-24 |
| 7/16 | 0.4375 | 11.11 | 7/16-14 | 1.814 | 7/16-20 |
| 1/2 | 0.5000 | 12.70 | 1/2-13 | 1.954 | 1/2-20 |
| 9/16 | 0.5625 | 14.29 | 9/16-12 | 2.117 | 9/16-18 |
| 5/8 | 0.6250 | 15.88 | 5/8-11 | 2.309 | 5/8-18 |
| 3/4 | 0.7500 | 19.05 | 3/4-10 | 2.540 | 3/4-16 |
| 7/8 | 0.8750 | 22.22 | 7/8-9 | 2.822 | 7/8-14 |
| 1 | 1.0000 | 25.40 | 1-8 | 3.175 | 1-12 (the source also prints 1-14 UNS) |
| 1-1/8 | 1.1250 | 28.57 | 1-1/8-7 | 3.629 | 1-12 |
| 1-1/4 | 1.2500 | 31.75 | 1-1/4-7 | 3.629 | 1-12 |
| 1-3/8 | 1.3750 | 34.92 | 1-3/8-6 | 4.233 | 1-12 |
| 1-1/2 | 1.5000 | 38.10 | 1-1/2-6 | 4.233 | 1-12 |
| 1-3/4 | 1.7500 | 44.45 | 1-3/4-5 | 5.080 | - |
| 2 | 2.0000 | 50.80 | 2-4.5 | 5.644 | - |
| 2-1/4 | 2.2500 | 57.15 | 2-1/4-4.5 | 5.644 | - |
| 2-1/2 | 2.5000 | 63.50 | 2-1/2-4 | 6.350 | - |
| 2-3/4 | 2.7500 | 69.85 | 2-3/4-4 | 6.350 | - |
| 3 | 3.0000 | 76.20 | 3-4 | 6.350 | - |
| 3-1/4 | 3.2500 | 82.55 | 3-1/4-4 | 6.350 | - |
| 3-1/2 | 3.5000 | 88.90 | 3-1/2-4 | 6.350 | - |
| 3-3/4 | 3.7500 | 95.25 | 3-3/4-4 | 6.350 | - |
| 4 | 4.0000 | 101.60 | 4-4 | 6.350 | - |
Mating features
Drawn at the exact size. Open press, slide, run and socket features by your process's clearance (tolerances by process); leave designed gaps and clamp fits as drawn.
| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| 1/4-20 rod | major diameter 6.35, 20 TPI (pitch 1.27 computed) | 1/4-20 UNC nut or tapped hole (see hex-nuts-inch) | designed | all |
| 3/8-16 rod | major diameter 9.525, 16 TPI (pitch 1.5875 computed) | 3/8-16 UNC nut or tapped hole | designed | all |
| 1/2-13 rod | major diameter 12.7, 13 TPI (pitch 1.954 computed) | 1/2-13 UNC nut or tapped hole | designed | all |
Where the files are
Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.
| Torqbolt | ASME B18.31.3 threaded rods: nominal diameters and UNC / UNF threads per inch, #4 to 5 in | web | Publisher's page; dimensions are facts |
| fasten.it | ASME B18.31.3 Standard dimensions for threaded rods, inch series: normal lengths 3, 6, 10, 12 ft and length tolerance | web | Publisher's page; dimensions are facts |
Xem scan
File coming
No downloadable true-size file yet: the published figures do not fix the whole shape, and Xem never guesses a number. A measured scan is planned; request it and it moves up.
https://xemstudio.com/mcp to Claude, ChatGPT, Cursor or any MCP client (free, no account, one minute) and it can look up exact sizes, mating fits and free STEP/STL from every chat.Plain text: sheet.txt · JSON: /api/geometry?object=threaded-rod-inch-unc-unf-sizes
Fits with
Questions
How many threads per inch is 1/4 threaded rod?
20 (1/4-20 UNC), or 28 (1/4-28 UNF).
What is the diameter of 1/2-13 threaded rod in mm?
12.7 mm major diameter, 13 threads per inch (pitch 1.954 mm computed).
What lengths does threaded rod come in?
Normally 3, 6, 10 and 12 ft, tolerance ±1/2 in for 6 ft and longer and ±1/4 in below 6 ft (ASME B18.31.3).
What is 3/8-16 threaded rod?
3/8 in (9.525 mm) coarse thread, 16 TPI (pitch 1.588 mm computed).