M3 Hex Bolt (Hex Head Bolt), ISO 4014

This page has 3 lengths from 20 to 30 mm, each as simplified and threaded STEP of the M3 × 0.5 hex bolt (ISO 4014), whose head is 5.32 to 5.5 mm across the flats and 2 mm high.

How these parts are made, and what the levels mean: read the method

• Also searched as: M3 bolt, M3 x 20 to M3 x 30 bolts
• Model id: iso4014-m3
• Standard: ISO 4014:2022 · thread M3 × 0.5, ISO metric coarse, right hand

Lengths

Length (mm)	Part key	Simplified	Threaded
20	iso4014-m3x20	STEP	STEP
25	iso4014-m3x25	STEP	STEP
30	iso4014-m3x30	STEP	STEP

Dimensions

Symbol	Name	min	nom	max	Modeled	Rule	Level
P	Thread pitch		0.5		0.5	nominal	L2
a	Thread run-out under the head (ISO 4017)	0.5		1.5	1	midpoint of min–max	L2
b	Thread length (ISO 4014)		12 ref		12	reference value	L2
c	Washer face height	0.15		0.4	0.275	midpoint of min–max	L2
da	Transition diameter			3.6	3.6	single limit (max), modeled at the limit	L2
ds	Shank diameter (ISO 4014)	2.86		3	2.93	midpoint of min–max	L2
dw	Bearing face diameter	4.84			4.84	single limit (min), modeled at the limit	L2
e	Width across corners	6.01			6.01	single limit (min), modeled at the limit	L2
k	Head height	1.875	2	2.125	2	nominal	L2
kw	Wrenching height	1.31			1.31	single limit (min), modeled at the limit	L2
beta	Head top chamfer angle	15		30	22.5	midpoint of min–max	L2
lf	Fillet transition length (ISO 4014)			1	1	single limit (max), modeled at the limit	L2
r	Underhead fillet radius	0.1			0.1	single limit (min), modeled at the limit	L2
s	Width across flats	5.32		5.5	5.41	midpoint of min–max	L2
P	Coarse thread pitch		0.5		0.5	nominal	L1
tap_drill	Tap drill diameter		2.5		2.5	nominal	L1
d1	Basic minor diameter		2.458734		2.458734	nominal	L1
ch_angle	Chamfered end angle			50	50	single limit (max), modeled at the limit	L2
dh_fine	Clearance hole, fine series		3.2		3.2	nominal	L1
dh_medium	Clearance hole, medium series		3.4		3.4	nominal	L1
dh_coarse	Clearance hole, coarse series		3.6		3.6	nominal	L1

Thread and holes

• Tap drill: 2.5 mm (method: d − P), L1, sources amesweb-tap-drill, rule-tap-drill.
• Clearance hole (ISO 273): close 3.2, normal 3.4, loose 3.6 mm (L1: fine, medium and coarse series (albany-clearance, wikipedia-de-clearance)).

Drawing

As a PDF: CC-ISO4014-SZ-M3.pdf.

Goes with the M3 hex bolt

• Spanner: 5.5 mm, the hexagon's maximum width across flats (s) in the table above.
• ISO 4032 hex nut, the same size as this M3 hex bolt: M3 Hex Nut (Hexagon Nut), ISO 4032 / DIN 934
• ISO 7089 flat washer, the same size as this M3 hex bolt: M3 Flat Washer (Plain Washer), ISO 7089

The M3 hex bolt beside the M2.5 and the M4

The M3 is number 3, counting from the smallest, of the 7 ISO 4014 hex bolts published here, from M2 to M8.

• Thread pitch (P): 0.5 mm on the M3 hex bolt, against 0.45 mm on the M2.5 and 0.7 mm on the M4.
• Thread run-out under the head (ISO 4017) (a): 0.5 to 1.5 mm on the M3 hex bolt, against 0.45 to 1.35 mm on the M2.5 and 0.7 to 2.1 mm on the M4.
• Thread length (ISO 4014) (b): 12 mm (reference) on the M3 hex bolt, against 11 mm (reference) on the M2.5 and 14 mm (reference) on the M4.
• Washer face height (c): 0.15 to 0.4 mm on the M3 hex bolt, against 0.1 to 0.25 mm on the M2.5 and 0.15 to 0.4 mm on the M4.
• Transition diameter (da): up to 3.6 mm on the M3 hex bolt, against up to 3.1 mm on the M2.5 and up to 4.7 mm on the M4.
• Shank diameter (ISO 4014) (ds): 2.86 to 3 mm on the M3 hex bolt, against 2.36 to 2.5 mm on the M2.5 and 3.82 to 4 mm on the M4.
• Bearing face diameter (dw): at least 4.84 mm on the M3 hex bolt, against at least 4.34 mm on the M2.5 and at least 6.2 mm on the M4.
• Width across corners (e): at least 6.01 mm on the M3 hex bolt, against at least 5.45 mm on the M2.5 and at least 7.66 mm on the M4.

Other sizes

• One size smaller: M2.5 Hex Bolt (Hex Head Bolt), ISO 4014, 4.82 to 5 mm across flats.
• One size larger: M4 Hex Bolt (Hex Head Bolt), ISO 4014, 6.78 to 7 mm across flats.

Documents

• CC-ISO4014-DS-M3.pdf: M3 datasheet: values with levels, lengths, sources
• CC-ISO4014-SZ-M3.pdf: M3 drawing: this size's values on the views
• parts.json: the part record of every length (the platform contract)

Sources

albany-clearance, amesweb-tap-drill, fasten-it-iso4014, fasten-it-iso4017, fasteners-eu-iso4017, fuller-iso4014, globalfastener-iso4017, globalfastener-iso4017-2022, iso4014-2022-sample, iso4014-2022-sample-lengths, iso4017-2022-sample, iso4017-2022-sample-figure, iso4753-2011-sample, rule-basic-minor, rule-iso4014-lg, rule-tap-drill, wikipedia-de-clearance, wikipedia-iso261. Full citations: the method page and this size's datasheet.

Found an error? Use the feedback section on this page.