Complete Thread Size Guide: Metric, UNC, UNF & BSP Dimensions with Tap Drill Sizes
Share
Whether you are designing a part, programming a CNC machine, or selecting the right masking plug for surface treatment, having accurate thread dimensions is critical. This comprehensive guide covers the exact major, pitch, and minor diameters — including tolerance min/max values — as well as tap drill sizes for the world's most common thread standards: ISO Metric (Coarse and Fine), Unified National (UNC and UNF), and British Standard Pipe (BSP/G). All values are per ISO 965-1 (metric) and ASME B1.1 (inch) standards.
When selecting silicone masking plugs for threaded holes, the general rule is to select a plug where the bottom diameter is slightly smaller than the thread's minor diameter, and the top diameter is slightly larger than the major diameter. This ensures a secure interference fit that prevents powder coating, e-coating, or plating liquids from entering the bore.
1. ISO Metric Coarse Threads (M) — Tolerance Class 6g / 6H
ISO metric coarse threads are the most widely used general-purpose thread standard globally, defined by ISO 261 and ISO 724. External thread tolerances are class 6g; internal thread tolerances are class 6H.
1a. External Threads (Bolts) — Class 6g
| Thread | Pitch (mm) | Major Ø Max (mm) | Major Ø Min (mm) | Pitch Ø Max (mm) | Pitch Ø Min (mm) | Minor Ø Max (mm) | Minor Ø Min (mm) | Tap Drill (mm) |
|---|---|---|---|---|---|---|---|---|
| M1 | 0.25 | 0.980 | 0.920 | 0.820 | 0.770 | 0.710 | 0.610 | 0.75 |
| M1.2 | 0.25 | 1.180 | 1.120 | 1.020 | 0.970 | 0.910 | 0.810 | 0.95 |
| M1.4 | 0.30 | 1.380 | 1.310 | 1.180 | 1.120 | 1.060 | 0.940 | 1.1 |
| M1.6 | 0.35 | 1.571 | 1.496 | 1.354 | 1.291 | 1.221 | 1.075 | 1.25 |
| M2 | 0.40 | 1.981 | 1.886 | 1.721 | 1.654 | 1.548 | 1.384 | 1.6 |
| M2.5 | 0.45 | 2.480 | 2.380 | 2.208 | 2.138 | 2.013 | 1.838 | 2.05 |
| M3 | 0.50 | 2.980 | 2.874 | 2.655 | 2.580 | 2.436 | 2.253 | 2.5 |
| M3.5 | 0.60 | 3.479 | 3.354 | 3.110 | 3.022 | 2.850 | 2.636 | 2.9 |
| M4 | 0.70 | 3.978 | 3.838 | 3.523 | 3.433 | 3.220 | 2.980 | 3.3 |
| M5 | 0.80 | 4.976 | 4.826 | 4.456 | 4.361 | 4.105 | 3.838 | 4.2 |
| M6 | 1.00 | 5.974 | 5.794 | 5.324 | 5.212 | 4.891 | 4.596 | 5.0 |
| M7 | 1.00 | 6.974 | 6.794 | 6.324 | 6.212 | 5.891 | 5.596 | 6.0 |
| M8 | 1.25 | 7.972 | 7.760 | 7.160 | 7.042 | 6.619 | 6.272 | 6.8 |
| M10 | 1.50 | 9.968 | 9.732 | 8.994 | 8.862 | 8.344 | 7.938 | 8.5 |
| M12 | 1.75 | 11.966 | 11.701 | 10.829 | 10.679 | 10.072 | 9.602 | 10.2 |
| M14 | 2.00 | 13.962 | 13.682 | 12.663 | 12.503 | 11.800 | 11.271 | 12.0 |
| M16 | 2.00 | 15.962 | 15.682 | 14.663 | 14.503 | 13.800 | 13.271 | 14.0 |
| M18 | 2.50 | 17.958 | 17.623 | 16.334 | 16.164 | 15.217 | 14.617 | 15.5 |
| M20 | 2.50 | 19.958 | 19.623 | 18.334 | 18.164 | 17.217 | 16.617 | 17.5 |
| M22 | 2.50 | 21.958 | 21.623 | 20.334 | 20.164 | 19.217 | 18.617 | 19.5 |
| M24 | 3.00 | 23.952 | 23.577 | 22.003 | 21.803 | 20.752 | 20.046 | 21.0 |
| M27 | 3.00 | 26.952 | 26.577 | 25.003 | 24.803 | 23.752 | 23.046 | 24.0 |
| M30 | 3.50 | 29.947 | 29.522 | 27.674 | 27.462 | 26.211 | 25.441 | 26.5 |
| M33 | 3.50 | 32.947 | 32.522 | 30.674 | 30.462 | 29.211 | 28.441 | 29.5 |
| M36 | 4.00 | 35.940 | 35.465 | 33.342 | 33.118 | 31.670 | 30.799 | 32.0 |
| M39 | 4.00 | 38.940 | 38.465 | 36.342 | 36.118 | 34.670 | 33.799 | 35.0 |
| M42 | 4.50 | 41.937 | 41.437 | 39.014 | 38.778 | 37.129 | 36.178 | 37.5 |
| M45 | 4.50 | 44.937 | 44.437 | 42.014 | 41.778 | 40.129 | 39.178 | 40.5 |
| M48 | 5.00 | 47.929 | 47.399 | 44.681 | 44.431 | 42.587 | 41.537 | 43.0 |
| M52 | 5.00 | 51.929 | 51.399 | 48.681 | 48.431 | 46.587 | 45.537 | 47.0 |
| M56 | 5.50 | 55.925 | 55.365 | 52.353 | 52.088 | 50.046 | 48.896 | 50.5 |
| M60 | 5.50 | 59.925 | 59.365 | 56.353 | 56.088 | 54.046 | 52.896 | 54.5 |
| M64 | 6.00 | 63.920 | 63.320 | 60.023 | 59.743 | 57.505 | 56.255 | 58.0 |
| M68 | 6.00 | 67.920 | 67.320 | 64.023 | 63.743 | 61.505 | 60.255 | 62.0 |
| M72 | 6.00 | 71.920 | 71.320 | 68.023 | 67.743 | 65.505 | 64.255 | 66.0 |
| M80 | 6.00 | 79.920 | 79.320 | 76.023 | 75.743 | 73.505 | 72.255 | 74.0 |
1b. Internal Threads (Nuts) — Class 6H
| Thread | Pitch (mm) | Major Ø Min (mm) | Major Ø Max (mm) | Pitch Ø Min (mm) | Pitch Ø Max (mm) | Minor Ø Min (mm) | Minor Ø Max (mm) |
|---|---|---|---|---|---|---|---|
| M1 | 0.25 | 1.000 | 1.095 | 0.838 | 0.908 | 0.729 | 0.785 |
| M1.2 | 0.25 | 1.200 | 1.295 | 1.038 | 1.108 | 0.929 | 0.985 |
| M1.4 | 0.30 | 1.400 | 1.510 | 1.205 | 1.283 | 1.075 | 1.142 |
| M1.6 | 0.35 | 1.600 | 1.736 | 1.373 | 1.458 | 1.221 | 1.321 |
| M2 | 0.40 | 2.000 | 2.148 | 1.740 | 1.830 | 1.567 | 1.679 |
| M2.5 | 0.45 | 2.500 | 2.660 | 2.208 | 2.303 | 2.013 | 2.138 |
| M3 | 0.50 | 3.000 | 3.172 | 2.675 | 2.775 | 2.459 | 2.599 |
| M3.5 | 0.60 | 3.500 | 3.699 | 3.110 | 3.222 | 2.850 | 3.010 |
| M4 | 0.70 | 4.000 | 4.219 | 3.545 | 3.663 | 3.242 | 3.422 |
| M5 | 0.80 | 5.000 | 5.240 | 4.480 | 4.605 | 4.134 | 4.334 |
| M6 | 1.00 | 6.000 | 6.300 | 5.350 | 5.500 | 4.917 | 5.153 |
| M7 | 1.00 | 7.000 | 7.300 | 6.350 | 6.500 | 5.917 | 6.153 |
| M8 | 1.25 | 8.000 | 8.376 | 7.188 | 7.348 | 6.647 | 6.912 |
| M10 | 1.50 | 10.000 | 10.400 | 9.026 | 9.206 | 8.376 | 8.676 |
| M12 | 1.75 | 12.000 | 12.450 | 10.863 | 11.063 | 10.106 | 10.441 |
| M14 | 2.00 | 14.000 | 14.500 | 12.701 | 12.913 | 11.835 | 12.210 |
| M16 | 2.00 | 16.000 | 16.500 | 14.701 | 14.913 | 13.835 | 14.210 |
| M18 | 2.50 | 18.000 | 18.600 | 16.376 | 16.600 | 15.294 | 15.744 |
| M20 | 2.50 | 20.000 | 20.600 | 18.376 | 18.600 | 17.294 | 17.744 |
| M22 | 2.50 | 22.000 | 22.600 | 20.376 | 20.600 | 19.294 | 19.744 |
| M24 | 3.00 | 24.000 | 24.700 | 22.051 | 22.316 | 20.752 | 21.252 |
| M27 | 3.00 | 27.000 | 27.700 | 25.051 | 25.316 | 23.752 | 24.252 |
| M30 | 3.50 | 30.000 | 30.800 | 27.727 | 28.007 | 26.211 | 26.771 |
| M33 | 3.50 | 33.000 | 33.800 | 30.727 | 31.007 | 29.211 | 29.771 |
| M36 | 4.00 | 36.000 | 36.900 | 33.402 | 33.702 | 31.670 | 32.270 |
| M39 | 4.00 | 39.000 | 39.900 | 36.402 | 36.702 | 34.670 | 35.270 |
| M42 | 4.50 | 42.000 | 43.000 | 39.077 | 39.402 | 37.129 | 37.799 |
| M45 | 4.50 | 45.000 | 46.000 | 42.077 | 42.402 | 40.129 | 40.799 |
| M48 | 5.00 | 48.000 | 49.100 | 44.752 | 45.102 | 42.587 | 43.297 |
| M52 | 5.00 | 52.000 | 53.100 | 48.752 | 49.102 | 46.587 | 47.297 |
| M56 | 5.50 | 56.000 | 57.200 | 52.428 | 52.803 | 50.046 | 50.796 |
| M60 | 5.50 | 60.000 | 61.200 | 56.428 | 56.803 | 54.046 | 54.796 |
| M64 | 6.00 | 64.000 | 65.300 | 60.103 | 60.503 | 57.505 | 58.305 |
| M68 | 6.00 | 68.000 | 69.300 | 64.103 | 64.503 | 61.505 | 62.305 |
| M72 | 6.00 | 72.000 | 73.300 | 68.103 | 68.503 | 65.505 | 66.305 |
| M80 | 6.00 | 80.000 | 81.300 | 76.103 | 76.503 | 73.505 | 74.305 |
2. ISO Metric Fine Threads (M×P) — Tolerance Class 6g
Metric fine threads have a smaller pitch for the same diameter, offering higher tensile strength and better vibration resistance. The designation includes the pitch (e.g., M10×1.25).
2. External Metric Fine Threads — Class 6g
| Thread | Pitch (mm) | Major Ø Max (mm) | Major Ø Min (mm) | Pitch Ø Max (mm) | Pitch Ø Min (mm) | Minor Ø Max (mm) | Minor Ø Min (mm) | Tap Drill (mm) |
|---|---|---|---|---|---|---|---|---|
| M8×1 | 1.00 | 7.974 | 7.794 | 7.324 | 7.212 | 6.891 | 6.596 | 7.0 |
| M10×1 | 1.00 | 9.974 | 9.794 | 9.324 | 9.212 | 8.891 | 8.596 | 9.0 |
| M10×1.25 | 1.25 | 9.972 | 9.760 | 9.160 | 9.042 | 8.619 | 8.272 | 8.75 |
| M12×1 | 1.00 | 11.974 | 11.794 | 11.324 | 11.212 | 10.891 | 10.596 | 11.0 |
| M12×1.25 | 1.25 | 11.972 | 11.760 | 11.160 | 11.042 | 10.619 | 10.272 | 10.75 |
| M12×1.5 | 1.50 | 11.968 | 11.732 | 10.994 | 10.862 | 10.344 | 9.938 | 10.5 |
| M14×1.5 | 1.50 | 13.968 | 13.732 | 12.994 | 12.862 | 12.344 | 11.938 | 12.5 |
| M16×1.5 | 1.50 | 15.968 | 15.732 | 14.994 | 14.862 | 14.344 | 13.938 | 14.5 |
| M18×1.5 | 1.50 | 17.968 | 17.732 | 16.994 | 16.862 | 16.344 | 15.938 | 16.5 |
| M20×1.5 | 1.50 | 19.968 | 19.732 | 18.994 | 18.862 | 18.344 | 17.938 | 18.5 |
| M22×1.5 | 1.50 | 21.968 | 21.732 | 20.994 | 20.862 | 20.344 | 19.938 | 20.5 |
| M24×1.5 | 1.50 | 23.968 | 23.732 | 22.994 | 22.862 | 22.344 | 21.938 | 22.5 |
| M24×2 | 2.00 | 23.962 | 23.682 | 22.663 | 22.503 | 21.800 | 21.271 | 22.0 |
| M27×2 | 2.00 | 26.962 | 26.682 | 25.663 | 25.503 | 24.800 | 24.271 | 25.0 |
| M30×2 | 2.00 | 29.962 | 29.682 | 28.663 | 28.503 | 27.800 | 27.271 | 28.0 |
| M33×2 | 2.00 | 32.962 | 32.682 | 31.663 | 31.503 | 30.800 | 30.271 | 31.0 |
| M36×2 | 2.00 | 35.962 | 35.682 | 34.663 | 34.503 | 33.800 | 33.271 | 34.0 |
| M36×3 | 3.00 | 35.952 | 35.577 | 34.003 | 33.803 | 32.752 | 32.046 | 33.0 |
| M42×2 | 2.00 | 41.962 | 41.682 | 40.663 | 40.503 | 39.800 | 39.271 | 40.0 |
| M42×3 | 3.00 | 41.952 | 41.577 | 40.003 | 39.803 | 38.752 | 38.046 | 39.0 |
| M48×2 | 2.00 | 47.962 | 47.682 | 46.663 | 46.503 | 45.800 | 45.271 | 46.0 |
| M48×3 | 3.00 | 47.952 | 47.577 | 46.003 | 45.803 | 44.752 | 44.046 | 45.0 |
3. Unified National Coarse (UNC) — Tolerance Class 2A
The Unified Thread Standard (ASME B1.1) is the primary thread standard in the United States and Canada. UNC is the coarse pitch series. Sizes below 1/4 inch use a gauge number designation (e.g., #8-32).
3. UNC External Threads — Class 2A
| Thread | TPI | Major Ø Max (in) | Major Ø Min (in) | Pitch Ø Max (in) | Pitch Ø Min (in) | Minor Ø Max (in) | Minor Ø Min (in) | Tap Drill |
|---|---|---|---|---|---|---|---|---|
| #0-80 | 80 | 0.0595 | 0.0563 | 0.0514 | 0.0496 | 0.0451 | 0.0422 | #56 / 1.19mm |
| #1-64 | 64 | 0.0724 | 0.0686 | 0.0623 | 0.0603 | 0.0538 | 0.0503 | #53 / 1.51mm |
| #2-56 | 56 | 0.0854 | 0.0813 | 0.0737 | 0.0715 | 0.0641 | 0.0602 | #50 / 1.78mm |
| #3-48 | 48 | 0.0983 | 0.0938 | 0.0847 | 0.0824 | 0.0734 | 0.0691 | #47 / 1.99mm |
| #4-40 | 40 | 0.1113 | 0.1062 | 0.0950 | 0.0925 | 0.0813 | 0.0764 | #43 / 2.26mm |
| #5-40 | 40 | 0.1243 | 0.1192 | 0.1080 | 0.1055 | 0.0943 | 0.0894 | #38 / 2.58mm |
| #6-32 | 32 | 0.1373 | 0.1315 | 0.1169 | 0.1140 | 0.1000 | 0.0942 | #36 / 2.71mm |
| #8-32 | 32 | 0.1633 | 0.1575 | 0.1429 | 0.1400 | 0.1260 | 0.1202 | #29 / 3.45mm |
| #10-24 | 24 | 0.1893 | 0.1822 | 0.1619 | 0.1585 | 0.1411 | 0.1340 | #25 / 3.80mm |
| #12-24 | 24 | 0.2153 | 0.2082 | 0.1879 | 0.1845 | 0.1671 | 0.1600 | #16 / 4.50mm |
| 1/4-20 | 20 | 0.2489 | 0.2408 | 0.2164 | 0.2127 | 0.1876 | 0.1798 | #7 / 5.10mm |
| 5/16-18 | 18 | 0.3110 | 0.3022 | 0.2752 | 0.2712 | 0.2414 | 0.2330 | F / 6.90mm |
| 3/8-16 | 16 | 0.3730 | 0.3637 | 0.3331 | 0.3287 | 0.2938 | 0.2847 | 5/16 / 7.94mm |
| 7/16-14 | 14 | 0.4351 | 0.4248 | 0.3896 | 0.3847 | 0.3447 | 0.3348 | U / 9.40mm |
| 1/2-13 | 13 | 0.4976 | 0.4867 | 0.4472 | 0.4422 | 0.3978 | 0.3871 | 27/64 / 10.72mm |
| 9/16-12 | 12 | 0.5600 | 0.5487 | 0.5065 | 0.5012 | 0.4528 | 0.4416 | 31/64 / 12.30mm |
| 5/8-11 | 11 | 0.6226 | 0.6106 | 0.5644 | 0.5589 | 0.5069 | 0.4950 | 17/32 / 13.49mm |
| 3/4-10 | 10 | 0.7476 | 0.7344 | 0.6832 | 0.6773 | 0.6219 | 0.6091 | 21/32 / 16.67mm |
| 7/8-9 | 9 | 0.8726 | 0.8584 | 0.7995 | 0.7932 | 0.7307 | 0.7167 | 49/64 / 19.45mm |
| 1-8 | 8 | 0.9976 | 0.9820 | 0.9142 | 0.9074 | 0.8376 | 0.8220 | 7/8 / 22.23mm |
| 1 1/8-7 | 7 | 1.1226 | 1.1054 | 1.0257 | 1.0182 | 0.9394 | 0.9218 | 63/64 / 25.00mm |
| 1 1/4-7 | 7 | 1.2476 | 1.2304 | 1.1507 | 1.1432 | 1.0644 | 1.0468 | 1 7/64 / 28.17mm |
| 1 3/8-6 | 6 | 1.3722 | 1.3528 | 1.2585 | 1.2500 | 1.1585 | 1.1390 | 1 7/32 / 31.00mm |
| 1 1/2-6 | 6 | 1.4972 | 1.4778 | 1.3835 | 1.3750 | 1.2835 | 1.2640 | 1 11/32 / 34.13mm |
| 1 3/4-5 | 5 | 1.7462 | 1.7238 | 1.6101 | 1.6001 | 1.4902 | 1.4673 | 1 9/16 / 39.69mm |
| 2-4.5 | 4.5 | 1.9952 | 1.9700 | 1.8476 | 1.8366 | 1.7094 | 1.6843 | 1 25/32 / 45.24mm |
4. Unified National Fine (UNF) — Tolerance Class 2A
UNF threads offer better tension adjustment, higher strength, and improved vibration resistance compared to UNC for the same nominal diameter.
4. UNF External Threads — Class 2A
| Thread | TPI | Major Ø Max (in) | Major Ø Min (in) | Pitch Ø Max (in) | Pitch Ø Min (in) | Minor Ø Max (in) | Minor Ø Min (in) | Tap Drill |
|---|---|---|---|---|---|---|---|---|
| #0-80 | 80 | 0.0595 | 0.0563 | 0.0514 | 0.0496 | 0.0451 | 0.0422 | #56 / 1.19mm |
| #1-72 | 72 | 0.0724 | 0.0689 | 0.0634 | 0.0615 | 0.0560 | 0.0527 | #53 / 1.51mm |
| #2-64 | 64 | 0.0854 | 0.0816 | 0.0753 | 0.0733 | 0.0671 | 0.0633 | #50 / 1.78mm |
| #3-56 | 56 | 0.0983 | 0.0942 | 0.0866 | 0.0844 | 0.0764 | 0.0723 | #45 / 2.08mm |
| #4-48 | 48 | 0.1113 | 0.1068 | 0.0977 | 0.0954 | 0.0864 | 0.0820 | #42 / 2.36mm |
| #5-44 | 44 | 0.1243 | 0.1195 | 0.1094 | 0.1069 | 0.0971 | 0.0924 | #37 / 2.64mm |
| #6-40 | 40 | 0.1373 | 0.1322 | 0.1209 | 0.1183 | 0.1073 | 0.1023 | #33 / 2.87mm |
| #8-36 | 36 | 0.1633 | 0.1577 | 0.1452 | 0.1424 | 0.1299 | 0.1245 | #29 / 3.45mm |
| #10-32 | 32 | 0.1893 | 0.1835 | 0.1688 | 0.1659 | 0.1519 | 0.1461 | #21 / 4.04mm |
| #12-28 | 28 | 0.2153 | 0.2088 | 0.1920 | 0.1887 | 0.1722 | 0.1657 | #14 / 4.62mm |
| 1/4-28 | 28 | 0.2489 | 0.2424 | 0.2256 | 0.2223 | 0.2058 | 0.1993 | #3 / 5.41mm |
| 5/16-24 | 24 | 0.3110 | 0.3039 | 0.2844 | 0.2808 | 0.2614 | 0.2540 | I / 6.76mm |
| 3/8-24 | 24 | 0.3730 | 0.3659 | 0.3464 | 0.3428 | 0.3234 | 0.3160 | Q / 8.33mm |
| 7/16-20 | 20 | 0.4351 | 0.4271 | 0.4027 | 0.3987 | 0.3757 | 0.3675 | 25/64 / 9.92mm |
| 1/2-20 | 20 | 0.4976 | 0.4896 | 0.4652 | 0.4612 | 0.4382 | 0.4300 | 29/64 / 11.51mm |
| 9/16-18 | 18 | 0.5601 | 0.5515 | 0.5248 | 0.5205 | 0.4943 | 0.4853 | 33/64 / 13.10mm |
| 5/8-18 | 18 | 0.6226 | 0.6140 | 0.5873 | 0.5830 | 0.5568 | 0.5478 | 37/64 / 14.68mm |
| 3/4-16 | 16 | 0.7476 | 0.7381 | 0.7082 | 0.7036 | 0.6733 | 0.6636 | 11/16 / 17.46mm |
| 7/8-14 | 14 | 0.8726 | 0.8621 | 0.8272 | 0.8221 | 0.7874 | 0.7769 | 13/16 / 20.64mm |
| 1-12 | 12 | 0.9976 | 0.9862 | 0.9432 | 0.9378 | 0.8978 | 0.8864 | 59/64 / 23.42mm |
| 1 1/8-12 | 12 | 1.1226 | 1.1112 | 1.0682 | 1.0628 | 1.0228 | 1.0114 | 1 3/64 / 26.59mm |
| 1 1/4-12 | 12 | 1.2476 | 1.2362 | 1.1932 | 1.1878 | 1.1478 | 1.1364 | 1 11/64 / 29.76mm |
| 1 3/8-12 | 12 | 1.3726 | 1.3612 | 1.3182 | 1.3128 | 1.2728 | 1.2614 | 1 19/64 / 32.94mm |
| 1 1/2-12 | 12 | 1.4976 | 1.4862 | 1.4432 | 1.4378 | 1.3978 | 1.3864 | 1 27/64 / 36.11mm |
5. British Standard Pipe Parallel (BSP / G) — ISO 228
BSP parallel (G) threads are used internationally for pipe and fluid system connections. The nominal size refers to the bore of the pipe, not the thread diameter. Parallel G threads require an O-ring or bonded seal for sealing — the thread itself does not seal.
| Thread | TPI | OD Max (mm) | OD Min (mm) | Pitch Ø Max (mm) | Pitch Ø Min (mm) | Minor Ø Max (mm) | Minor Ø Min (mm) | Tap Drill (mm) |
|---|---|---|---|---|---|---|---|---|
| G 1/16 | 28 | 7.723 | 7.638 | 7.142 | 7.072 | 6.561 | 6.461 | 6.8 |
| G 1/8 | 28 | 9.728 | 9.643 | 9.147 | 9.077 | 8.566 | 8.466 | 8.8 |
| G 1/4 | 19 | 13.157 | 13.045 | 12.301 | 12.211 | 11.445 | 11.295 | 11.8 |
| G 3/8 | 19 | 16.662 | 16.550 | 15.806 | 15.716 | 14.950 | 14.800 | 15.3 |
| G 1/2 | 14 | 20.955 | 20.820 | 19.793 | 19.683 | 18.631 | 18.431 | 19.1 |
| G 5/8 | 14 | 22.911 | 22.776 | 21.749 | 21.639 | 20.587 | 20.387 | 21.1 |
| G 3/4 | 14 | 26.441 | 26.306 | 25.279 | 25.169 | 24.117 | 23.917 | 24.6 |
| G 7/8 | 14 | 30.201 | 30.066 | 29.039 | 28.929 | 27.877 | 27.677 | 28.4 |
| G 1 | 11 | 33.249 | 33.089 | 31.770 | 31.640 | 30.291 | 30.041 | 30.8 |
| G 1 1/4 | 11 | 41.910 | 41.750 | 40.431 | 40.301 | 38.952 | 38.702 | 39.5 |
| G 1 1/2 | 11 | 47.803 | 47.643 | 46.324 | 46.194 | 44.845 | 44.595 | 45.4 |
| G 2 | 11 | 59.614 | 59.454 | 58.135 | 58.005 | 56.656 | 56.406 | 57.2 |
| G 2 1/2 | 11 | 75.184 | 75.024 | 73.705 | 73.575 | 72.226 | 71.976 | 72.8 |
| G 3 | 11 | 87.884 | 87.724 | 86.405 | 86.275 | 84.926 | 84.676 | 85.5 |
| G 4 | 11 | 113.300 | 113.140 | 111.820 | 111.690 | 110.340 | 110.090 | 110.9 |
How to Choose Masking Plugs Based on Thread Size
When selecting a silicone plug to mask a threaded hole during surface treatment, you must account for the thread's minor and major diameters. A standard tapered silicone plug should have:
- A bottom diameter 10% to 15% smaller than the thread's minor diameter to allow easy insertion.
- A top diameter 10% to 15% larger than the thread's major diameter to ensure it stops securely and seals the chamfer.
For high-volume production, flanged silicone thread plugs or hollow pull plugs are often preferred, as they are specifically moulded to match the thread pitch diameter and provide a flush seal against the surrounding surface. For blind holes where a standard plug cannot be fully inserted, tapered silicone plugs with a handle allow secure placement and easy removal after coating.