UNJ threads (UNJC and UNJF): size chart
Full chart with the tap drill for every size. Press “Calculate” on any row to open the calculator with that thread.
UNJ is the aerospace version of the Unified thread (AS8879): same diameters and pitches as UNC (UNJC) and UNF (UNJF), but with the thread root rounded to a controlled radius, which lowers stress concentration and resists fatigue better. To make room for that radius the nut minor Ø is larger than in UN, so the drill is not the UNC or UNF one.
| Thread | Threads per inch | Ø major | Min. internal minor Ø (UNJ) | Internal minor Ø in UN | Calculate |
|---|---|---|---|---|---|
| #1-64 UNJC | 64 | 0.073" · 1.854 mm | 0.0578" · 1.467 mm | 0.0561" · 1.424 mm | |
| #2-56 UNJC | 56 | 0.086" · 2.184 mm | 0.0686" · 1.742 mm | 0.0667" · 1.693 mm | |
| #3-48 UNJC | 48 | 0.099" · 2.515 mm | 0.0787" · 1.999 mm | 0.0765" · 1.942 mm | |
| #4-40 UNJC | 40 | 0.112" · 2.845 mm | 0.0876" · 2.226 mm | 0.085" · 2.158 mm | |
| #5-40 UNJC | 40 | 0.125" · 3.175 mm | 0.1006" · 2.556 mm | 0.098" · 2.488 mm | |
| #6-32 UNJC | 32 | 0.138" · 3.505 mm | 0.1076" · 2.732 mm | 0.1042" · 2.646 mm | |
| #8-32 UNJC | 32 | 0.164" · 4.166 mm | 0.1336" · 3.393 mm | 0.1302" · 3.307 mm | |
| #10-24 UNJC | 24 | 0.19" · 4.826 mm | 0.1494" · 3.795 mm | 0.1449" · 3.68 mm | |
| #12-24 UNJC | 24 | 0.216" · 5.486 mm | 0.1754" · 4.455 mm | 0.1709" · 4.34 mm | |
| 1/4"-20 UNJC | 20 | 0.25" · 6.35 mm | 0.2013" · 5.113 mm | 0.1959" · 4.975 mm | |
| 5/16"-18 UNJC | 18 | 0.3125" · 7.938 mm | 0.2584" · 6.563 mm | 0.2524" · 6.41 mm | |
| 3/8"-16 UNJC | 16 | 0.375" · 9.525 mm | 0.3141" · 7.978 mm | 0.3073" · 7.806 mm | |
| 7/16"-14 UNJC | 14 | 0.4375" · 11.113 mm | 0.3679" · 9.345 mm | 0.3602" · 9.149 mm | |
| 1/2"-13 UNJC | 13 | 0.5" · 12.7 mm | 0.425" · 10.796 mm | 0.4167" · 10.585 mm | |
| 9/16"-12 UNJC | 12 | 0.5625" · 14.288 mm | 0.4813" · 12.226 mm | 0.4723" · 11.997 mm | |
| 5/8"-11 UNJC | 11 | 0.625" · 15.875 mm | 0.5364" · 13.625 mm | 0.5266" · 13.375 mm | |
| 3/4"-10 UNJC | 10 | 0.75" · 19.05 mm | 0.6526" · 16.575 mm | 0.6417" · 16.3 mm | |
| 7/8"-9 UNJC | 9 | 0.875" · 22.225 mm | 0.7667" · 19.475 mm | 0.7547" · 19.17 mm | |
| 1"-8 UNJC | 8 | 1" · 25.4 mm | 0.8782" · 22.307 mm | 0.8647" · 21.963 mm | |
| 1-1/8"-7 UNJC | 7 | 1.125" · 28.575 mm | 0.9858" · 25.04 mm | 0.9704" · 24.647 mm | |
| 1-1/4"-7 UNJC | 7 | 1.25" · 31.75 mm | 1.1108" · 28.215 mm | 1.0954" · 27.822 mm | |
| 1-3/8"-6 UNJC | 6 | 1.375" · 34.925 mm | 1.2126" · 30.801 mm | 1.1946" · 30.342 mm | |
| 1-1/2"-6 UNJC | 6 | 1.5" · 38.1 mm | 1.3376" · 33.976 mm | 1.3196" · 33.517 mm | |
| 1-3/4"-5 UNJC | 5 | 1.75" · 44.45 mm | 1.5552" · 39.501 mm | 1.5335" · 38.951 mm | |
| 2"-4.5 UNJC | 4.5 | 2" · 50.8 mm | 1.7835" · 45.301 mm | 1.7594" · 44.69 mm |
| Thread | Threads per inch | Ø major | Min. internal minor Ø (UNJ) | Internal minor Ø in UN | Calculate |
|---|---|---|---|---|---|
| #0-80 UNJF | 80 | 0.06" · 1.524 mm | 0.0478" · 1.215 mm | 0.0465" · 1.18 mm | |
| #1-72 UNJF | 72 | 0.073" · 1.854 mm | 0.0594" · 1.51 mm | 0.058" · 1.472 mm | |
| #2-64 UNJF | 64 | 0.086" · 2.184 mm | 0.0707" · 1.797 mm | 0.0691" · 1.754 mm | |
| #3-56 UNJF | 56 | 0.099" · 2.515 mm | 0.0816" · 2.073 mm | 0.0797" · 2.024 mm | |
| #4-48 UNJF | 48 | 0.112" · 2.845 mm | 0.0917" · 2.329 mm | 0.0894" · 2.272 mm | |
| #5-44 UNJF | 44 | 0.125" · 3.175 mm | 0.1029" · 2.613 mm | 0.1004" · 2.55 mm | |
| #6-40 UNJF | 40 | 0.138" · 3.505 mm | 0.1136" · 2.886 mm | 0.1109" · 2.818 mm | |
| #8-36 UNJF | 36 | 0.164" · 4.166 mm | 0.137" · 3.479 mm | 0.1339" · 3.402 mm | |
| #10-32 UNJF | 32 | 0.19" · 4.826 mm | 0.1596" · 4.053 mm | 0.1562" · 3.967 mm | |
| #12-28 UNJF | 28 | 0.216" · 5.486 mm | 0.1812" · 4.602 mm | 0.1773" · 4.504 mm | |
| 1/4"-28 UNJF | 28 | 0.25" · 6.35 mm | 0.2152" · 5.466 mm | 0.2113" · 5.368 mm | |
| 5/16"-24 UNJF | 24 | 0.3125" · 7.938 mm | 0.2719" · 6.907 mm | 0.2674" · 6.792 mm | |
| 3/8"-24 UNJF | 24 | 0.375" · 9.525 mm | 0.3344" · 8.494 mm | 0.3299" · 8.379 mm | |
| 7/16"-20 UNJF | 20 | 0.4375" · 11.113 mm | 0.3888" · 9.876 mm | 0.3834" · 9.738 mm | |
| 1/2"-20 UNJF | 20 | 0.5" · 12.7 mm | 0.4513" · 11.463 mm | 0.4459" · 11.325 mm | |
| 9/16"-18 UNJF | 18 | 0.5625" · 14.288 mm | 0.5084" · 12.913 mm | 0.5024" · 12.76 mm | |
| 5/8"-18 UNJF | 18 | 0.625" · 15.875 mm | 0.5709" · 14.5 mm | 0.5648" · 14.347 mm | |
| 3/4"-16 UNJF | 16 | 0.75" · 19.05 mm | 0.6891" · 17.503 mm | 0.6823" · 17.331 mm | |
| 7/8"-14 UNJF | 14 | 0.875" · 22.225 mm | 0.8054" · 20.457 mm | 0.7977" · 20.261 mm | |
| 1"-12 UNJF | 12 | 1" · 25.4 mm | 0.9188" · 23.338 mm | 0.9098" · 23.109 mm | |
| 1-1/8"-12 UNJF | 12 | 1.125" · 28.575 mm | 1.0438" · 26.513 mm | 1.0348" · 26.284 mm | |
| 1-1/4"-12 UNJF | 12 | 1.25" · 31.75 mm | 1.1688" · 29.688 mm | 1.1598" · 29.459 mm | |
| 1-3/8"-12 UNJF | 12 | 1.375" · 34.925 mm | 1.2938" · 32.863 mm | 1.2848" · 32.634 mm | |
| 1-1/2"-12 UNJF | 12 | 1.5" · 38.1 mm | 1.4188" · 36.038 mm | 1.4098" · 35.809 mm |
How to read the chart
Minimum internal minor Ø: the smallest the tapped hole may be according to AS8879 (D − 0.97428·P). In UN it would be D − 1.08253·P, so the UNJ hole is larger.
The drill must leave the hole within the minor Ø tolerance of class 3B, and it is given by the UNJ tap data sheet. With a UNC or UNF drill the hole is too small and the root radius does not form properly.
"Calculate" opens the calculator with that size for the cycle and feed; check the thread with a UNJ gauge.
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