ISO Metric Fine Thread Chart
Basic dimensions for the most common ISO metric fine pitch threads (ISO 724 / DIN 13), from M6 to M64 — pitch, major, pitch and minor diameter, and recommended tap drill size.
Fine-pitch metric threads use the same 60° ISO profile as coarse threads, but a smaller pitch for a given major diameter — e.g. M12 coarse is M12×1.75, while common fine options are M12×1.5, M12×1.25 or M12×1. Unlike coarse threads, the pitch is always stated explicitly in a fine-thread designation.
Engineers reach for fine pitch when they need a larger stress area for a given outer diameter, finer linear adjustment per turn, or a thread shallow enough to fit a thin-walled tube or boss — common in hydraulic and pneumatic fittings, automotive steering and brake components, and precision instruments.
The trade-off: fine threads are more prone to cross-threading and galling, take more turns to assemble, and have a smaller torque margin before stripping — which is why coarse pitch stays the default for everyday fasteners subject to frequent assembly and disassembly.
| Size | Pitch (mm) | Major Ø (mm) | Pitch Ø (mm) | Minor Ø — bolt (mm) | Minor Ø — nut (mm) | Tap drill (mm) |
|---|---|---|---|---|---|---|
| M6×0.75 | 0.75 | 6.00 | 5.513 | 5.080 | 5.188 | 5.20 |
| M8×1 | 1.00 | 8.00 | 7.350 | 6.773 | 6.917 | 7.00 |
| M10×1 | 1.00 | 10.00 | 9.350 | 8.773 | 8.917 | 9.00 |
| M10×1.25 | 1.25 | 10.00 | 9.188 | 8.466 | 8.647 | 8.80 |
| M12×1 | 1.00 | 12.00 | 11.350 | 10.773 | 10.917 | 11.00 |
| M12×1.25 | 1.25 | 12.00 | 11.188 | 10.466 | 10.647 | 10.80 |
| M12×1.5 | 1.50 | 12.00 | 11.026 | 10.160 | 10.376 | 10.50 |
| M14×1.25 | 1.25 | 14.00 | 13.188 | 12.466 | 12.647 | 12.80 |
| M14×1.5 | 1.50 | 14.00 | 13.026 | 12.160 | 12.376 | 12.50 |
| M16×1.5 | 1.50 | 16.00 | 15.026 | 14.160 | 14.376 | 14.50 |
| M18×1.5 | 1.50 | 18.00 | 17.026 | 16.160 | 16.376 | 16.50 |
| M18×2 | 2.00 | 18.00 | 16.701 | 15.546 | 15.835 | 16.00 |
| M20×1.5 | 1.50 | 20.00 | 19.026 | 18.160 | 18.376 | 18.50 |
| M20×2 | 2.00 | 20.00 | 18.701 | 17.546 | 17.835 | 18.00 |
| M22×1.5 | 1.50 | 22.00 | 21.026 | 20.160 | 20.376 | 20.50 |
| M24×1.5 | 1.50 | 24.00 | 23.026 | 22.160 | 22.376 | 22.50 |
| M24×2 | 2.00 | 24.00 | 22.701 | 21.546 | 21.835 | 22.00 |
| M27×1.5 | 1.50 | 27.00 | 26.026 | 25.160 | 25.376 | 25.50 |
| M27×2 | 2.00 | 27.00 | 25.701 | 24.546 | 24.835 | 25.00 |
| M30×1.5 | 1.50 | 30.00 | 29.026 | 28.160 | 28.376 | 28.50 |
| M30×2 | 2.00 | 30.00 | 28.701 | 27.546 | 27.835 | 28.00 |
| M33×1.5 | 1.50 | 33.00 | 32.026 | 31.160 | 31.376 | 31.50 |
| M33×2 | 2.00 | 33.00 | 31.701 | 30.546 | 30.835 | 31.00 |
| M36×2 | 2.00 | 36.00 | 34.701 | 33.546 | 33.835 | 34.00 |
| M36×3 | 3.00 | 36.00 | 34.051 | 32.319 | 32.752 | 33.00 |
| M39×3 | 3.00 | 39.00 | 37.051 | 35.319 | 35.752 | 36.00 |
| M42×3 | 3.00 | 42.00 | 40.051 | 38.319 | 38.752 | 39.00 |
| M45×3 | 3.00 | 45.00 | 43.051 | 41.319 | 41.752 | 42.00 |
| M48×3 | 3.00 | 48.00 | 46.051 | 44.319 | 44.752 | 45.00 |
| M52×3 | 3.00 | 52.00 | 50.051 | 48.319 | 48.752 | 49.00 |
| M56×4 | 4.00 | 56.00 | 53.402 | 51.093 | 51.670 | 52.00 |
| M60×4 | 4.00 | 60.00 | 57.402 | 55.093 | 55.670 | 56.00 |
| M64×4 | 4.00 | 64.00 | 61.402 | 59.093 | 59.670 | 60.00 |
No thread size matches your search.
Values follow ISO 724 basic-profile formulas and the standard fine pitches listed in DIN 13-2/3/4. One or two of the most common pitches per diameter are shown — several sizes support additional finer options not listed here. Data provided for reference — always verify against the current standard for critical or safety-related applications.
Understanding the columns
- Major diameter
- The largest diameter of the thread — at the crest of an external (bolt) thread, or the root of an internal (nut) thread.
- Pitch
- The distance between two adjacent thread crests. For fine threads, the pitch is always stated explicitly in the designation — a bare "M12" means the coarse pitch, never a fine one.
- Pitch diameter
- The diameter at which the thread groove and ridge widths are equal. It's the diameter used to define thread fit and tolerance class.
- Minor diameter
- The smallest diameter of the thread — at the root of an external thread, or the crest of an internal one.
- Tap drill
- The recommended drill diameter for the hole before tapping, sized for roughly 75% thread engagement.
Frequently asked questions
What's the difference between a coarse and fine metric thread of the same diameter?
Both share the same 60° profile and major diameter, but the fine version uses a smaller pitch, giving it a larger pitch and minor diameter (more thread engagement area) and a shallower thread depth per turn. They are not interchangeable — a fine nut will not run on a coarse bolt of the same nominal size.
When is fine pitch the better engineering choice over coarse?
Use fine pitch when wall thickness is limited (thin tube or boss), when maximum tensile strength is needed for a given outer diameter, or when fine linear adjustment resolution is required (micrometers, precision slides). It's also the norm in hydraulic and pneumatic fitting standards.
Do fine threads need a dedicated tap, die and mating part?
Yes. Because pitch, pitch diameter and minor diameter all differ from the coarse thread of the same nominal size, fine threads require their own tap/die and a nut or mating part cut to the same pitch — there is no cross-compatibility with coarse-pitch hardware.
Why aren't fine threads the default for general-purpose fasteners?
Fine threads are more sensitive to cross-threading, take more turns to run down, and are more prone to galling and stripping under over-torque due to shallower engagement per turn. Coarse threads are more forgiving for repeated assembly and disassembly and in dirty or corroded conditions, so ISO 724 makes coarse the general-purpose default and reserves fine pitch for the benefits above.
References & further reading
- ISO 724:2023 — ISO general purpose metric screw threads, basic dimensions — the standard this chart's fine-pitch profile formulas are built from.
- DIN 13-2:1999 — ISO general purpose metric screw threads, fine pitch series — defines the standard nominal fine-pitch sizes for diameters 1–50 mm.
- ISO metric screw thread — Wikipedia — background on the thread profile and designation system.
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