Metric Threads

Reference data and engineering information about metric threads for miscellaneous applications.

metricthreads

Overview

Engineering reference data for Metric Threads in miscellaneous.

Key Formulas

Unit Conversion

$y = x \cdot k$

Multiply by conversion factor.

Linear Interpolation

$y = y_1 + \frac{(x - x_1)(y_2 - y_1)}{x_2 - x_1}$

Estimate between two known points.

Percentage

$p = \frac{\text{part}}{\text{whole}} \times 100\%$

Part as fraction of whole.

Variables

Symbol	Description	Unit
$x$	Input value	—
$y$	Output value	—
$k$	Conversion factor	—

ISO 724 Metric Coarse Threads (Selected Sizes)
Size (Nominal Diameter)(mm)	Pitch(mm)	Clearance Drill(mm)	Tap Drill(mm)	Tensile Stress Area(mm²)
M 1.6	0.35	1.8	1.25	—
M 2	0.4	2.4	1.6	—
M 2.5	0.45	2.9	2	—
M 3	0.5	3.4	2.5	—
M 3.5	0.6	3.9	2.9	—
M 4	0.7	4.5	3.3	8.78
M 5	0.8	5.5	4.2	14.2
M 6	1	6.6	5	20.1
M 8	1.25	9	6.8	36.6
M 10	1.5	12	8.5	58
M 12	1.75	14	10.2	84.3
M 14	2	16	12	—
M 16	2	18	14	157
M 20	2.5	22	17.5	245
M 22	2.5	25	19.5	—
M 24	3	27	21	353
M 27	3	30	24	—
M 30	3.5	33	26.5	561
M 36	4	40	32	817
M 42	4.5	46	37.5	1120
M 48	5	53	43	1470
M 56	5.5	62	50.5	2030
M 64	6	70	58	2680
M 68	6	74	62	—

ISO 724 Metric Fine Threads (Selected Sizes)
Size	Pitch(mm)	Tap Drill(mm)	Tensile Stress Area(mm²)
M 8 x 0.75	0.75	7.2	—
M 8 x 1.0	1	7	39.2
M 10 x 0.75	0.75	9.2	—
M 10 x 1	1	9	64.5
M 10 x 1.25	1.25	8.8	61.2
M 12 x 1.5	1.5	10.5	88.1
M 12 x 1.25	1.25	10.8	92.1
M 16 x 1	1	15	178
M 16 x 1.5	1.5	14.5	167
M 20 x 1.5	1.5	18.5	272
M 20 x 2.0	2	18	258
M 24 x 1.5	1.5	22.5	401
M 24 x 2.0	2	22	384
M 30 x 2.0	2	28	621
M 30 x 3.0	3	27	581
M 36 x 2.0	2	34	915
M 36 x 3.0	3	33	865
M 42 x 3.0	3	39	1210
M 42 x 4.0	4	38	1150
M 48 x 3.0	3	45	1600
M 48 x 4.0	4	44	1540

Core Thread Properties & Formulas

Key geometric properties of the standard metric thread profile.

Thread Angle: The included angle of the thread form is 60°.

Thread Depth: The depth of the thread (from crest to root) is proportional to the pitch. $\text{Thread Depth} \approx 0.614 \times P$ Where P is the thread pitch in mm.

Tensile Stress Area: The critical area used to calculate the tensile strength of a bolt or screw. It is defined by the formula: $A_s = \frac{\pi}{4} \left( d_2 - \frac{0.9382 \cdot P}{2} \right)^2$ Where:

$A_s$ = Tensile Stress Area (mm²)
$d_2$ = Pitch diameter of the thread (mm)
$P$ = Pitch (mm)

Key Definitions

Nominal Diameter (d): The primary, specified diameter of the thread (e.g., M10 has a nominal diameter of 10 mm). It roughly corresponds to the major diameter of an external thread.
Pitch (P): The distance, measured parallel to the thread axis, between corresponding points on adjacent threads.
Clearance Drill: The recommended drill size for creating a through-hole that a bolt of the given size can pass through without binding.
Tap Drill: The recommended drill size for creating a hole that can be threaded (tapped) to accept a bolt of the given size.

Metric Threads

Overview

Key Formulas

Unit Conversion

Linear Interpolation

Percentage

Variables

Metric Thread Dimensions

Coarse Threads

Fine Threads

Core Thread Properties & Formulas

Key Definitions

Interactive Charts

Bolt Metric Thread

Metric coarse threads - clearance and tap drill size

References