M8 Socket Head Cap Screw (Allen Bolt), ISO 4762 / DIN 912

An M8 socket head cap screw (ISO 4762) has a head 12.73 to 13 mm across and 7.64 to 8 mm tall, driven with a 6 mm hex key. This page has 14 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
• Equivalent standards: DIN 912 (as listed by fasteners.eu); the values here are ISO 4762's.
• Model id: iso4762-m8
• Standard: ISO 4762:2004 · thread M8 × 1.25, ISO metric coarse, right hand

Lengths

Length (mm)	Part key	Simplified	Threaded
12	iso4762-m8x12	STEP	STEP
16	iso4762-m8x16	STEP	STEP
20	iso4762-m8x20	STEP	STEP
25	iso4762-m8x25	STEP	STEP
30	iso4762-m8x30	STEP	STEP
35	iso4762-m8x35	STEP	STEP
40	iso4762-m8x40	STEP	STEP
45	iso4762-m8x45	STEP	STEP
50	iso4762-m8x50	STEP	STEP
55	iso4762-m8x55	STEP	STEP
60	iso4762-m8x60	STEP	STEP
65	iso4762-m8x65	STEP	STEP
70	iso4762-m8x70	STEP	STEP
80	iso4762-m8x80	STEP	STEP

Dimensions

Symbol	Name	min	nom	max	Modeled	Rule	Level
P	Thread pitch		1.25		1.25	nominal	L1
b	Thread length	28	28 ref		28	reference value	L1
dk	Head diameter, plain head	12.73		13	12.865	midpoint of min–max	L1
dk_knurled	Head diameter, knurled head			13.27	13.27	single limit (max), modeled at the limit	L1
da	Transition diameter			9.2	9.2	single limit (max), modeled at the limit	L1
ds	Shank diameter	7.78		8	7.89	midpoint of min–max	L1
e	Socket width across corners	6.863			6.863	single limit (min), modeled at the limit	L1
k	Head height	7.64		8	7.82	midpoint of min–max	L1
r	Underhead fillet radius	0.4		0.6	0.5	midpoint of min–max	L0 (max: one source)
s	Socket width across flats	6.02	6	6.14	6.08	midpoint of min–max	L1
t	Socket depth	4			4	single limit (min), modeled at the limit	L1
lf	Underhead fillet length			1.02	1.02	single limit (max), modeled at the limit	L0 (max: one source)
v	Head top chamfer or radius			0.8	0.8	single limit (max), modeled at the limit	L1
dw	Bearing face diameter	12.33			12.33	single limit (min), modeled at the limit	L1
w	Wall thickness	3.3			3.3	single limit (min), modeled at the limit	L1
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-ISO4762-SZ-M8.pdf.

Goes with the M8 socket head cap screw

• Hex key: 6 mm, the socket's nominal width across flats (s) in the table above.
• ISO 4032 hex nut, the same size as this M8 socket head cap screw: M8 Hex Nut (Hexagon Nut), ISO 4032 / DIN 934
• ISO 7089 flat washer, the same size as this M8 socket head cap screw: M8 Flat Washer (Plain Washer), ISO 7089

Approximate mass

Approximate mass of 1000 screws by length, from fasten.it's DIN EN ISO 4762 mass table (fasten-it-iso4762), which it captions “Approximate mass, in kg x1000 pcs, (ρ=7,85 kg/dm3)”.

Length l (mm)	mass per 1000 (kg)
12	10.9
16	12.1
20	13.4
25	15
30	16.9
35	18.9
40	20.9
45	22.9
50	24.9
55	26.9
60	28.9
65	31
70	33
80	37

The M8 socket head cap screw beside the M6

The M8 is the largest of the 7 ISO 4762 socket head cap screws published here, from M2 to M8.

• Thread pitch (P): 1.25 mm on the M8 socket head cap screw, against 1 mm on the M6.
• Thread length (b): at least 28 mm on the M8 socket head cap screw, against at least 24 mm on the M6.
• Head diameter, plain head (dk): 12.73 to 13 mm on the M8 socket head cap screw, against 9.78 to 10 mm on the M6.
• Head diameter, knurled head (dk_knurled): up to 13.27 mm on the M8 socket head cap screw, against up to 10.22 mm on the M6.
• Transition diameter (da): up to 9.2 mm on the M8 socket head cap screw, against up to 6.8 mm on the M6.
• Shank diameter (ds): 7.78 to 8 mm on the M8 socket head cap screw, against 5.82 to 6 mm on the M6.
• Socket width across corners (e): at least 6.863 mm on the M8 socket head cap screw, against at least 5.723 mm on the M6.
• Head height (k): 7.64 to 8 mm on the M8 socket head cap screw, against 5.7 to 6 mm on the M6.

Other sizes

• One size smaller: M6 Socket Head Cap Screw (Allen Bolt), ISO 4762 / DIN 912, 9.78 to 10 mm head, 5 mm hex key.

Documents

• CC-ISO4762-DS-M8.pdf: M8 datasheet: values with levels, lengths, sources
• CC-ISO4762-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-iso4762, amesweb-iso4762-lengths, amesweb-tap-drill, fasten-it-iso4762, fasteners-eu-iso4762, fasteners-eu-iso4762-lengths, iso4753-2011-sample, opac-iso4762, 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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