Metric (M) Thread Chart: Choosing the Right Bolt Thread Size for Your CNC Design

Metric bolt sizes follow ISO standards for thread dimensions, ensuring compatibility across components. They are the most commonly used thread type in general applications and CNC machining, and are essentially the standard for screws, bolts, tapped holes, and mechanical assemblies. Common ISO metric thread sizes include M6, M8, and M12.

Metric (M) threads are available in different series: coarse (M), fine (MF), and extra fine (MEF). To help you select the appropriate size and thread type for your project, this article provides an overview of metric thread tables, highlights the advantages and disadvantages of various pitches, and recommends suitable bolt sizes for different applications. Key columns in the tables include:

Nominal Size (d=D): Outer diameter of the bolt (e.g., M1 = 1 mm).
Pitch (p): Distance between adjacent threads (e.g., for M1, it’s 0.25 mm).
r: Root radius (the inner edge of the thread).
d2 (D2): Minor diameter (root of the thread).
d3: Diameter of the thread’s crest (the outermost point).
D1: Major diameter (outer diameter).
h3: Thread height.
H1: External thread height (distance from the base of the thread to the peak).
Tap Drill: The drill size required for tapping the thread (in mm).

Pitch, root, diameter, thread height, drill tap in metric thread chart

Metric Thread Table – Coarse Pitch (M1-M68)

This chart outlines the dimensions for coarse pitch thread sizes, ranging from M1 to M68. Coarse (M) threads have fewer threads per inch, making them ideal for softer materials like wood or plastic.

Nominal Size	d=D (mm)	p (mm)	r (mm)	d2=D2 (mm)	d3 (mm)	D1 (mm)	h3 (mm)	H1 (mm)	Tap Drill (mm)
M1	1	0.25	0.036	0.838	0.693	0.729	0.153	0.135	0.75
M1.1	1.1	0.25	0.036	0.938	0.793	0.829	0.153	0.135	0.85
M1.2	1.2	0.25	0.036	1.038	0.893	0.929	0.153	0.135	0.95
M1.4	1.4	0.3	0.043	1.205	1.032	1.075	0.184	0.162	1.1
M1.6	1.6	0.35	0.051	1.373	1.171	1.221	0.215	0.189	1.25
M1.8	1.8	0.35	0.051	1.573	1.371	1.421	0.215	0.189	1.45
M2	2	0.4	0.058	1.74	1.509	1.567	0.245	0.217	1.6
M2.2	2.2	0.45	0.065	1.908	1.648	1.713	0.276	0.244	1.75
M2.5	2.5	0.45	0.065	2.208	1.948	2.013	0.276	0.244	2.05
M3	3	0.5	0.072	2.675	2.387	2.459	0.307	0.271	2.5
M3.5	3.5	0.6	0.087	3.11	2.764	2.85	0.368	0.325	2.9
M4	4	0.7	0.101	3.545	3.141	3.242	0.429	0.379	3.3
M4.5	4.5	0.75	0.108	4.013	3.58	3.688	0.46	0.406	3.8
M5	5	0.8	0.115	4.48	4.019	4.134	0.491	0.433	4.2
M6	6	1	0.144	5.35	4.773	4.917	0.613	0.541	5
M7	7	1	0.144	6.35	5.773	5.917	0.613	0.541	6
M8	8	1.25	0.18	7.188	6.466	6.647	0.767	0.677	6.8
M9	9	1.25	0.18	8.188	7.466	7.647	0.767	0.677	7.8
M10	10	1.5	0.217	9.026	8.16	8.376	0.92	0.812	8.5
M11	11	1.5	0.217	10.026	9.16	9.376	0.92	0.812	9.5
M12	12	1.75	0.253	10.863	9.853	10.106	1.074	0.947	10.2
M14	14	2	0.289	12.701	11.546	11.835	1.227	1.083	12
M16	16	2	0.289	14.701	13.546	13.835	1.227	1.083	14
M18	18	2.5	0.361	16.376	14.933	15.394	1.534	1.353	15.5
M20	20	2.5	0.361	18.376	16.933	17.294	1.534	1.353	17.5
M22	22	2.5	0.361	20.376	18.933	19.294	1.534	1.353	19.5
M24	24	3	0.433	22.051	20.319	20.752	1.84	1.624	21
M27	27	3	0.433	25.051	23.319	23.752	1.84	1.624	24
M30	30	3.5	0.505	27.727	25.706	26.211	2.147	1.894	26.5
M33	33	3.5	0.505	30.727	28.706	29.211	2.147	1.894	29.5
M36	36	4	0.577	33.402	31.093	31.67	2.454	2.165	32
M39	39	4	0.577	36.402	34.093	34.67	2.454	2.165	35
M42	42	4.5	0.65	39.077	36.479	37.129	2.76	2.436	37.5
M48	48	5	0.722	44.752	41.866	42.857	3.067	2.706	43
M52	52	5	0.722	48.752	45.866	46.587	3.067	2.706	47
M56	56	5.5	0.794	52.428	49.252	50.046	3.374	2.977	50.5
M60	60	5.5	0.794	56.428	53.252	54.046	3.374	2.977	54.5
M64	64	6	0.866	60.103	56.639	57.505	3.681	3.248	58
M68	68	6	0.866	64.103	60.639	61.505	3.681	3.248	62

Advantages of Coarse Threads

Easier and cheaper to machine.
Less prone to stripping and cross threading.
Less susceptible to being damaged and can still work with ‘nicks’ in the thread.
Faster to install, ideal for parts that need frequent assembly and disassembly.

Disadvantages of Coarse Threads

Not as strong as a corresponding fine-pitch thread.
More vulnerable to loosening under vibration.
Not ideal for threading into thin-walled parts.

‍

Metric Thread Table – Fine Pitch (M1-M64)

This chart outlines the dimensions for fine pitch thread sizes, ranging from M1 to M68. Fine (MF) threads have a smaller pitch (i.e., threads are more closely spaced) than coarse threads, making them ideal for metals or thin-walled components

Nominal Size	d=D (mm)	p (mm)	r (mm)	d2=D2 (mm)	d3 (mm)	D1 (mm)	h3 (mm)	H1 (mm)	Tap Drill (mm)
M1.0x0.2	1	0.2	0.029	0.87	0.755	0.783	0.123	0.108	0.8
M1.1×0.2	1.1	0.2	0.029	0.97	0.855	0.883	0.123	0.108	0.9
M1.2×0.2	1.2	0.2	0.029	1.07	0.955	0.983	0.123	0.108	1
M1.4×0.2	1.4	0.2	0.029	1.27	1.155	1.183	0.123	0.108	1.2
M1.6×0.2	1.6	0.2	0.029	1.47	1.355	1.383	0.123	0.108	1.4
M1.8×0.2	1.8	0.2	0.029	1.67	1.555	1.583	0.123	0.108	1.6
M2x0.25	2	0.25	0.036	1.838	1.693	1.729	0.153	0.135	1.75
M2.2×0.25	2.2	0.25	0.036	2.038	1.893	1.929	0.153	0.135	1.95
M2.5×0.35	2.5	0.35	0.051	2.273	2.071	2.121	0.215	0.189	2.1
M3x0.35	3	0.35	0.051	2.773	2.571	2.621	0.215	0.189	2.6
M3.5×0.35	3.5	0.35	0.051	3.273	3.071	3.121	0.215	0.189	3.1
M4x0.5	4	0.5	0.072	3.675	3.387	3.459	0.307	0.271	3.5
M4.5×0.5	4.5	0.5	0.072	4.175	3.887	3.959	0.307	0.271	4
M5x0.5	5	0.5	0.072	4.675	4.387	4.459	0.307	0.271	4.5
M5.5×0.5	5.5	0.5	0.072	5.175	4.887	4.959	0.307	0.271	5
M6x0.75	6	0.75	0.108	5.513	5.08	5.188	0.46	0.406	5.2
M7x0.75	7	0.75	0.108	6.513	6.08	6.188	0.46	0.406	6.2
M8x0.75	8	0.75	0.108	7.513	7.08	7.188	0.46	0.406	7.2
M8x1.0	8	1	0.144	7.35	6.773	6.917	0.613	0.541	7
M9x0.75	9	0.75	0.108	8.513	8.08	8.188	0.46	0.406	8.2
M9x1.0	9	1	0.144	8.35	7.773	7.917	0.613	0.541	8
M10x0.75	10	0.75	0.108	9.513	9.08	9.188	0.46	0.406	9.2
M10x1.0	10	1	0.144	9.35	8.773	8.917	0.613	0.541	9
M10x1.25	10	1.25	0.18	9.188	8.466	8.647	0.767	0.677	8.8
M11x0.75	11	0.75	0.108	10.513	10.08	10.188	0.46	0.406	10.2
M11x1.0	11	1	0.144	10.35	9.773	9.917	0.613	0.541	10
M12x1.0	12	1	0.144	11.35	10.773	10.917	0.613	0.541	11
M12x1.25	12	1.25	0.18	11.188	10.466	10.647	0.767	0.677	10.8
M12x1.5	12	1.5	0.217	11.026	10.16	10.376	0.92	0.812	10.5

Nominal Size	d=D (mm)	p (mm)	r (mm)	d2=D2 (mm)	d3 (mm)	D1 (mm)	h3 (mm)	H1 (mm)	Tap Drill (mm)
M14x1.0	14	1	0.144	13.35	12.773	12.917	0.613	0.541	13
M14x1.25	14	1.25	0.18	13.188	12.466	12.647	0.767	0.677	12.8
M14x1.5	14	1.5	0.217	13.026	12.16	12.376	0.92	0.812	12.5
M15x1.0	15	1	0.144	14.35	13.773	13.917	0.613	0.541	14
M15x1.5	15	1.5	0.217	14.026	13.16	13.376	0.92	0.812	13.5
M16x1.0	16	1	0.144	15.35	14.773	14.917	0.613	0.541	15
M16x1.5	16	1.5	0.217	15.026	14.16	14.376	0.92	0.812	14.5
M17x1.0	17	1	0.144	16.35	15.773	15.917	0.613	0.541	16
M17x1.5	17	1.5	0.217	16.026	15.16	15.376	0.92	0.812	15.5
M18x1.0	18	1	0.144	17.35	16.773	16.917	0.613	0.541	17
M18x1.5	18	1.5	0.217	17.026	16.16	16.376	0.92	0.812	16.5
M18x2.0	18	2	0.289	16.701	15.546	15.835	1.227	1.083	16
M20x1.0	20	1	0.144	19.35	18.773	18.917	0.613	0.541	19
M20x1.5	20	1.5	0.217	19.026	18.16	18.376	0.92	0.812	18.5
M20x2.0	20	2	0.289	18.701	17.546	17.835	1.227	1.083	18
M22x1.0	22	1	0.144	21.35	20.773	20.917	0.613	0.541	21
M22x1.5	22	1.5	0.217	21.026	20.16	20.376	0.92	0.812	20.5
M22x2.0	22	2	0.289	20.701	19.546	19.835	1.227	1.083	20
M24x1.0	24	1	0.144	23.35	22.773	22.917	0.613	0.541	23
M24x1.5	24	1.5	0.217	23.026	22.16	22.376	0.92	0.812	22.5
M24x2.0	24	2	0.289	22.701	21.546	21.835	1.227	1.083	22
M25x1.0	25	1	0.144	24.35	23.773	23.917	0.613	0.541	24
M25x1.5	25	1.5	0.217	24.026	23.16	23.376	0.92	0.812	23.5
M25x2.0	25	2	0.289	23.701	22.546	22.835	1.227	1.083	23
M27x1.0	27	1	0.144	26.35	25.773	25.917	0.613	0.541	26
M27x1.5	27	1.5	0.217	26.026	25.16	25.376	0.92	0.812	25.5
M27x2.0	27	2	0.289	25.701	24.546	24.835	1.227	1.083	25
M28x1.0	28	1	0.144	27.35	26.773	26.917	0.613	0.541	27
M28x1.5	28	1.5	0.217	27.026	26.16	26.376	0.92	0.812	26.5
M28x2.0	28	2	0.289	26.701	25.546	25.835	1.227	1.083	26

Nominal Size	d=D (mm)	p (mm)	r (mm)	d2=D2 (mm)	d3 (mm)	D1 (mm)	h3 (mm)	H1 (mm)	Tap Drill (mm)
M30x1.0	30	1	0.144	29.35	28.773	28.917	0.613	0.541	29
M30x1.5	30	1.5	0.217	29.026	28.16	28.376	0.92	0.812	28.5
M30x2.0	30	2	0.289	28.701	27.546	27.835	1.227	1.083	28
M30x3.0	30	3	0.433	28.051	26.319	26.752	1.84	1.624	27
M32x1.5	32	1.5	0.217	31.026	30.16	30.376	0.92	0.812	30.5
M32x2.0	32	2	0.289	30.701	29.546	29.835	1.227	1.083	30
M33x1.5	33	1.5	0.217	32.026	31.16	31.376	0.92	0.812	31.5
M33x2.0	33	2	0.289	31.701	30.546	30.835	1.227	1.083	31
M33x3.0	33	3	0.433	31.051	29.319	29.752	1.84	1.624	30
M35x1.5	35	1.5	0.217	34.026	33.16	33.376	0.92	0.812	33.5
M35x2.0	35	2	0.289	33.701	32.546	32.835	1.227	1.083	33
M36x1.5	36	1.5	0.217	35.026	34.16	34.376	0.92	0.812	34.5
M36x2.0	36	2	0.289	34.701	33.546	33.835	1.227	1.083	34
M36x3.0	36	3	0.433	34.051	32.319	32.752	1.84	1.624	33
M39x1.5	39	1.5	0.217	38.026	37.16	37.376	0.92	0.812	37.5
M39x2.0	39	2	0.289	37.701	36.546	36.835	1.227	1.083	37
M39x3.0	39	3	0.433	37.051	35.319	35.752	1.84	1.624	36
M40x1.5	40	1.5	0.217	39.026	38.16	38.376	0.92	0.812	38.5
M40x2.0	40	2	0.289	38.701	37.546	37.835	1.227	1.083	38
M40x3.0	40	3	0.433	38.051	36.619	36.752	1.84	1.624	37
M42x1.5	42	1.5	0.217	41.026	40.16	40.376	0.92	0.812	40.5
M42x2.0	42	2	0.289	40.701	39.546	39.835	1.227	1.083	40
M42x3.0	42	3	0.433	40.051	38.319	38.752	1.84	1.624	39
M42x4.0	42	4	0.577	39.402	37.093	37.67	2.454	2.165	38
M45x1.5	45	1.5	0.217	44.026	43.16	43.376	0.92	0.812	43.5
M45x2.0	45	2	0.289	43.701	42.546	42.835	1.227	1.083	43
M45x3.0	45	3	0.433	43.051	41.319	41.752	1.84	1.624	42
M45x4.0	45	4	0.577	42.402	40.093	40.67	2.454	2.165	41
M48x1.5	48	1.5	0.217	47.026	46.16	46.376	0.92	0.812	46.5
M48x2.0	48	2	0.289	46.701	45.546	45.835	1.227	1.083	46
M48x3.0	48	3	0.433	46.051	44.319	44.752	1.84	1.624	45
M48x4.0	48	4	0.577	45.402	43.093	43.67	2.454	2.165	44

Nominal Size	d=D (mm)	p (mm)	r (mm)	d2=D2 (mm)	d3 (mm)	D1 (mm)	h3 (mm)	H1 (mm)	Tap Drill (mm)
M50x1.5	50	1.5	0.217	49.026	48.16	48.376	0.92	0.812	48.5
M50x2.0	50	2	0.289	48.701	47.546	47.835	1.227	1.083	48
M50x3.0	50	3	0.433	48.051	46.319	46.752	1.84	1.624	47
M52x1.5	52	1.5	0.217	51.026	50.16	50.376	0.92	0.812	50.5
M52x2.0	52	2	0.289	50.701	49.546	49.835	1.227	1.083	50
M52x3.0	52	3	0.433	50.051	48.319	48.752	1.84	1.624	49
M52x4.0	52	4	0.577	49.402	47.093	47.67	2.454	2.165	48
M55x1.5	55	1.5	0.217	54.026	53.16	53.376	0.92	0.812	53.5
M55x2.0	55	2	0.289	53.701	52.546	52.835	1.227	1.083	53
M55x3.0	55	3	0.433	53.051	51.319	51.752	1.84	1.624	52
M55x4.0	55	4	0.577	52.402	50.093	50.67	2.454	2.165	51
M56x1.5	56	1.5	0.217	55.026	54.16	54.376	0.92	0.812	54.5
M56x2.0	56	2	0.289	54.701	43.546	53.835	1.227	1.083	54
M56x3.0	56	3	0.433	54.051	52.319	52.752	1.84	1.624	53
M56x4.0	56	4	0.577	53.402	51.903	51.67	2.454	2.165	52
M58x1.5	58	1.5	0.217	57.026	56.16	56.376	0.92	0.812	56.5
M58x2.0	58	2	0.289	56.701	55.546	55.835	1.227	1.083	56
M58x3.0	58	3	0.433	56.051	54.319	54.752	1.84	1.624	55
M58x4.0	58	4	0.577	55.402	53.093	53.67	2.454	2.165	54
M60x1.5	60	1.5	0.217	59.026	58.16	58.376	0.92	0.812	58.5
M60x2.0	60	2	0.289	58.701	57.546	57.835	1.227	1.083	58
M60x3.0	60	3	0.433	58.051	56.319	56.752	1.84	1.624	57
M60x4.0	60	4	0.577	57.402	55.093	55.67	2.454	2.165	56
M62x1.5	62	1.5	0.217	61.026	60.16	60.376	0.92	0.812	60.5
M62x2.0	62	2	0.289	60.701	59.546	59.835	1.227	1.083	60
M62x3.0	62	3	0.433	60.051	58.319	58.752	1.84	1.624	59
M62x4.0	62	4	0.577	59.402	57.093	57.67	2.454	2.165	58
M64x1.5	64	1.5	0.217	63.026	62.16	62.376	0.92	0.812	62.5
M64x2.0	64	2	0.289	62.701	61.546	61.835	1.227	1.083	62
M64x3.0	64	3	0.433	62.051	60.319	60.752	1.84	1.624	61
M64x4.0	64	4	0.577	61.402	59.093	59.67	2.454	2.165	60

Advantages of Fine Threads

Stronger than a coarse pitch thread in tension.
Offer better resistance to loosening under vibration.
Requires less torque to achieve the same level of preload (clamping force) as coarse threads.
The smaller pitch allows for finer adjustment for applications that require precise adjustment.

Disadvantages of Fine Threads

Takes more turns to screw and unscrew.
More prone to cross-threading and stripping (in soft materials).
More susceptible to being damaged from contaminates.

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Extra Fine Pitch

Extra Fine (MEF) threads have very small pitches, much smaller than fine threads, which are designed to offer better precision and resistance to wear.

Advantages of Extra Fine Threads

Provide even more precise adjustments than fine threads.
Provide better resistance to loosening under vibration compared to coarse or even fine threads.
Ideal for applications needing high precision.
Suitable for miniature or precision assemblies.

Disadvantages of Extra Fine Threads

Like fine threads, it requires more turns to install and uninstall.
More prone to cross-threading and stripping than fine threads.
More expensive and difficult to machine.
Not suitable for high speed assembly.

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Metric (M) Thread Chart: Choosing a Bolt Thread Size For Your CNC Design

Metric Thread Table – Coarse Pitch (M1-M68)

Advantages of Coarse Threads

Disadvantages of Coarse Threads

Metric Thread Table – Fine Pitch (M1-M64)

Advantages of Fine Threads

Disadvantages of Fine Threads

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Extra Fine Pitch

Advantages of Extra Fine Threads

Disadvantages of Extra Fine Threads

Upload CAD Drawing, Source Custom Threaded Parts

Thread Types to Use for CNC Designs and Manufacturing

Metric (M) Thread Chart: Choosing the Right Bolt Thread Size for Your CNC Design

Design Guide: Adding Drafts—Best Practices for Better Mould Release

HDPE Injection Moulding Material

How to Design Bosses for Plastic Parts: Injection Moulding Design Guide

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