M8 Button Head Screw (Button Head Allen Bolt), ISO 7380-1

Driven with a 5 mm hex key, the M8 button head screw (ISO 7380-1) has a head 13.57 to 14 mm across and 4.1 to 4.4 mm tall. Its M8 × 1.25 thread comes in 13 lengths from 12 to 80 mm, each as simplified and threaded STEP.

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

• Also searched as: M8 bolt, M8 x 12 to M8 x 80 bolts
• Model id: iso7380-m8
• Standard: ISO 7380-1:2011 · thread M8 × 1.25, ISO metric coarse, right hand

Lengths

Length (mm)	Part key	Simplified	Threaded
12	iso7380-m8x12	STEP	STEP
16	iso7380-m8x16	STEP	STEP
20	iso7380-m8x20	STEP	STEP
25	iso7380-m8x25	STEP	STEP
30	iso7380-m8x30	STEP	STEP
35	iso7380-m8x35	STEP	STEP
40	iso7380-m8x40	STEP	STEP
45	iso7380-m8x45	STEP	STEP
50	iso7380-m8x50	STEP	STEP
55	iso7380-m8x55	STEP	STEP
60	iso7380-m8x60	STEP	STEP
70	iso7380-m8x70	STEP	STEP
80	iso7380-m8x80	STEP	STEP

Dimensions

Symbol	Name	min	nom	max	Modeled	Rule	Level
P	Thread pitch		1.25		1.25	nominal	L2
b	Thread length		28 ref		28	reference value	L2
da	Transition diameter			9.2	9.2	single limit (max), modeled at the limit	L2
dk	Head diameter	13.57		14	13.785	midpoint of min–max	L2
dL	Head top diameter		7.7 ref		7.7	reference value	L2
ds	Shank diameter	7.78		8	7.89	midpoint of min–max	L2
dw	Bearing face diameter	13.07			13.07	single limit (min), modeled at the limit	L2
e	Socket width across corners	5.723			5.723	single limit (min), modeled at the limit	L2
k	Head height	4.1		4.4	4.25	midpoint of min–max	L2
rf	Head dome radius	7.45		7.95	7.7	midpoint of min–max	L2
rs	Underhead fillet radius, plain shank	0.4			0.4	single limit (min), modeled at the limit	L2
rt	Underhead fillet radius, fully threaded	0.7			0.7	single limit (min), modeled at the limit	L2
s	Socket width across flats	5.02	5	5.14	5.08	midpoint of min–max	L2
t	Socket depth	2.6			2.6	single limit (min), modeled at the limit	L2
w	Wall thickness	1.05			1.05	single limit (min), modeled at the limit	L2
P	Coarse thread pitch		1.25		1.25	nominal	L1
tap_drill	Tap drill diameter		6.75		6.75	nominal	L1
d1	Basic minor diameter		6.646835		6.646835	nominal	L1
ch_angle	Chamfered end angle			50	50	single limit (max), modeled at the limit	L2
dh_fine	Clearance hole, fine series		8.4		8.4	nominal	L1
dh_medium	Clearance hole, medium series		9		9	nominal	L1
dh_coarse	Clearance hole, coarse series		10		10	nominal	L1

Thread and holes

• Tap drill: 6.75 mm (method: d − P), L1, sources amesweb-tap-drill, rule-tap-drill.
• Clearance hole (ISO 273): close 8.4, normal 9, loose 10 mm (L1: fine, medium and coarse series (albany-clearance, wikipedia-de-clearance)).

Drawing

As a PDF: CC-ISO7380-SZ-M8.pdf.

Goes with the M8 button head screw

• Hex key: 5 mm, the socket's nominal width across flats (s) in the table above.
• ISO 4032 hex nut, the same size as this M8 button head screw: M8 Hex Nut (Hexagon Nut), ISO 4032 / DIN 934
• ISO 7089 flat washer, the same size as this M8 button head screw: M8 Flat Washer (Plain Washer), ISO 7089

The M8 button head screw beside the M6

The M8 is the largest of the 5 ISO 7380-1 button head screws published here, from M3 to M8.

• Thread pitch (P): 1.25 mm on the M8 button head screw, against 1 mm on the M6.
• Thread length (b): 28 mm (reference) on the M8 button head screw, against 24 mm (reference) on the M6.
• Transition diameter (da): up to 9.2 mm on the M8 button head screw, against up to 6.8 mm on the M6.
• Head diameter (dk): 13.57 to 14 mm on the M8 button head screw, against 10.07 to 10.5 mm on the M6.
• Head top diameter (dL): 7.7 mm (reference) on the M8 button head screw, against 6 mm (reference) on the M6.
• Shank diameter (ds): 7.78 to 8 mm on the M8 button head screw, against 5.82 to 6 mm on the M6.
• Bearing face diameter (dw): at least 13.07 mm on the M8 button head screw, against at least 9.57 mm on the M6.
• Socket width across corners (e): at least 5.723 mm on the M8 button head screw, against at least 4.583 mm on the M6.

Other sizes

• One size smaller: M6 Button Head Screw (Button Head Allen Bolt), ISO 7380-1, 10.07 to 10.5 mm head, 4 mm hex key.

Documents

• CC-ISO7380-DS-M8.pdf: M8 datasheet: values with levels, lengths, sources
• CC-ISO7380-SZ-M8.pdf: M8 drawing: this size's values on the views
• parts.json: the part record of every length (the platform contract)

Sources

albany-clearance, amesweb-iso7380-1, amesweb-iso7380-1-lengths, amesweb-tap-drill, bossard-bn19-lengths, fasten-it-iso7380-1, fasteners-eu-iso7380-1, iso4753-2011-sample, iso7380-1-2011-sample, iso7380-1-2011-sample-lengths, rule-basic-minor, rule-tap-drill, wikipedia-de-clearance, wikipedia-iso261. Full citations: the method page and this size's datasheet.

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