Thread series · Metric fine

ISO Metric Fine Thread Chart — All Sizes, Dimensions & Tap Drills

Name: ISO Metric Fine thread dimensions and tap drill sizes
Creator: ShopMath

https://shopmath.org/threads/metric-fine · data verified August 1, 2026

The ISO Metric Fine series covers 37 standard sizes, from M1.6×0.2 to M64×4, and 37 of them carry a tap drill recommendation. ISO 261 fine metric pitches, for thin walls and vibration resistance.

Sizes: 37
Smallest: M1.6×0.2
Largest: M64×4
Standard: ISO 68-1, ISO 261, ISO 262, ISO 965-1, ISO 898-1

Every Metric fine Thread Size — Dimensions and Tap Drills

37 sizes, ordered smallest to largest. Every row links to the full page for that thread, with class limits, clearance holes and tap drills across 50–85% engagement.

ISO Metric Fine thread sizes — basic dimensions and tap drills
Property	Property	Major Ø		Pitch Ø		Minor Ø		Tap drill
Thread	Pitch mm	in	mm	in	mm	in	mm	Drill	in	mm
M1.6×0.2	0.200	0.0630	1.600	0.0579	1.470	0.0544	1.383	1.4 mm	0.0551	1.400
M1.8×0.2	0.200	0.0709	1.800	0.0658	1.670	0.0623	1.583	1.6 mm	0.0630	1.600
M2×0.25	0.250	0.0787	2.000	0.0724	1.838	0.0681	1.729	1.75 mm	0.0689	1.750
M2.5×0.35	0.350	0.0984	2.500	0.0895	2.273	0.0835	2.121	2.15 mm	0.0847	2.150
M3×0.35	0.350	0.1181	3.000	0.1092	2.773	0.1032	2.621	2.65 mm	0.1043	2.650
M3.5×0.35	0.350	0.1378	3.500	0.1289	3.273	0.1229	3.121	3.2 mm	0.1260	3.200
M4×0.5	0.500	0.1575	4.000	0.1447	3.675	0.1362	3.459	3.5 mm	0.1378	3.500
M5×0.5	0.500	0.1968	5.000	0.1841	4.675	0.1756	4.459	4.5 mm	0.1772	4.500
M6×0.75	0.750	0.2362	6.000	0.2170	5.513	0.2042	5.188	5.3 mm	0.2087	5.300
M7×0.75	0.750	0.2756	7.000	0.2564	6.513	0.2436	6.188	6.3 mm	0.2480	6.300
M8×0.75	0.750	0.3150	8.000	0.2958	7.513	0.2830	7.188	7.3 mm	0.2874	7.300
M8×1	1.000	0.3150	8.000	0.2894	7.350	0.2723	6.917	7 mm	0.2756	7.000
M10×1	1.000	0.3937	10.000	0.3681	9.350	0.3511	8.917	9 mm	0.3543	9.000
M10×1.25	1.250	0.3937	10.000	0.3617	9.188	0.3404	8.647	8.8 mm	0.3465	8.800
M12×1.25	1.250	0.4724	12.000	0.4405	11.188	0.4192	10.647	10.8 mm	0.4252	10.800
M12×1.5	1.500	0.4724	12.000	0.4341	11.026	0.4085	10.376	10.5 mm	0.4134	10.500
M14×1.5	1.500	0.5512	14.000	0.5128	13.026	0.4872	12.376	12.5 mm	0.4921	12.500
M16×1.5	1.500	0.6299	16.000	0.5916	15.026	0.5660	14.376	14.5 mm	0.5709	14.500
M18×1.5	1.500	0.7087	18.000	0.6703	17.026	0.6447	16.376	16.5 mm	0.6496	16.500
M18×2	2.000	0.7087	18.000	0.6575	16.701	0.6234	15.835	16 mm	0.6299	16.000
M20×1.5	1.500	0.7874	20.000	0.7491	19.026	0.7235	18.376	18.5 mm	0.7284	18.500
M20×2	2.000	0.7874	20.000	0.7363	18.701	0.7022	17.835	18 mm	0.7087	18.000
M22×1.5	1.500	0.8661	22.000	0.8278	21.026	0.8022	20.376	20.5 mm	0.8071	20.500
M22×2	2.000	0.8661	22.000	0.8150	20.701	0.7809	19.835	20 mm	0.7874	20.000
M24×2	2.000	0.9449	24.000	0.8937	22.701	0.8597	21.835	22 mm	0.8661	22.000
M27×2	2.000	1.0630	27.000	1.0118	25.701	0.9778	24.835	25 mm	0.9842	25.000
M30×2	2.000	1.1811	30.000	1.1300	28.701	1.0959	27.835	25 mm	0.9842	25.000
M33×2	2.000	1.2992	33.000	1.2481	31.701	1.2140	30.835	25 mm	0.9842	25.000
M36×3	3.000	1.4173	36.000	1.3406	34.051	1.2894	32.752	25 mm	0.9842	25.000
M39×3	3.000	1.5354	39.000	1.4587	37.051	1.4076	35.752	25 mm	0.9842	25.000
M42×3	3.000	1.6535	42.000	1.5768	40.051	1.5257	38.752	25 mm	0.9842	25.000
M45×3	3.000	1.7716	45.000	1.6949	43.051	1.6438	41.752	25 mm	0.9842	25.000
M48×3	3.000	1.8898	48.000	1.8130	46.051	1.7619	44.752	25 mm	0.9842	25.000
M52×4	4.000	2.0472	52.000	1.9450	49.402	1.8768	47.670	25 mm	0.9842	25.000
M56×4	4.000	2.2047	56.000	2.1024	53.402	2.0343	51.670	25 mm	0.9842	25.000
M60×4	4.000	2.3622	60.000	2.2599	57.402	2.1917	55.670	25 mm	0.9842	25.000
M64×4	4.000	2.5197	64.000	2.4174	61.402	2.3492	59.670	25 mm	0.9842	25.000

Basic dimensions are the theoretical values before a tolerance class is applied. Tap drills are for cut taps at the default engagement; per-size pages carry 50–85%.

Sources and Method for the Metric fine Thread Chart

Metric fine thread dimensionscomputed+compiled

ISO 68-1 basic profile and ISO 898-1 tensile stress area; verified in docs/research/data-sourcing.md §3.2; diameter/pitch pairs: ISO 261 / ISO 262 diameter-pitch pairs via Wikipedia (CC BY-SA 4.0); cross-checked against threadlib metric_thread.csv (BSD-3) and FreeCAD CAM metric-internal-6H.csv (LGPL-2.1+); clearance holes: ISO 273 (metric) and ASME B18.2.8 (inch) via FreeCAD FeatureHole.cpp (LGPL-2.1+), cross-checked against bd_warehouse clearance_hole_sizes.csv (Apache-2.0)

Verified against threadlib metric_thread.csv (BSD-3-Clause) and FreeCAD CAM metric-internal-6H.csv (LGPL-2.1+), agreeing cell-for-cell — 215 checks passed at 0.001 mm

Part computed from the standard's formulas, part compiled from agreeing public sources.

Assumptions

Tap drill figures are for cut taps at the default thread engagement; each size page carries the full 50–85% range.
Dataset scope: EXCLUDED: ISO 965-1 tolerance-grade formulas (not located — data-sourcing.md open item 2), 6g external limits (single-sourced), form tap drills, M68-M100 (verified demand cliff at M64).

Data last verified

August 1, 2026

How this data is built and checked →

How to Cite This Metric fine Thread Chart

Citation

ShopMath. "ISO Metric Fine Thread Chart — All Sizes, Dimensions & Tap Drills." ShopMath, verified August 1, 2026, https://shopmath.org/threads/metric-fine

BibTeX

@misc{shopmath-threads-metric-fine,
  title        = {ISO Metric Fine Thread Chart — All Sizes, Dimensions & Tap Drills},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/threads/metric-fine}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/threads/metric-fine

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