M2.5 Socket Head Cap Screw (Allen Bolt), ISO 4762 / DIN 912

Driven with a 2 mm hex key, the M2.5 socket head cap screw (ISO 4762) has a head 4.32 to 4.5 mm across and 2.36 to 2.5 mm tall. Its M2.5 × 0.45 thread comes in 9 lengths from 4 to 25 mm, each as simplified and threaded STEP.

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

• Also searched as: M2.5 bolt, M2.5 x 4 to M2.5 x 25 bolts
• Equivalent standards: DIN 912 (as listed by fasteners.eu); the values here are ISO 4762's.
• Model id: iso4762-m2-5
• Standard: ISO 4762:2004 · thread M2.5 × 0.45, ISO metric coarse, right hand

Lengths

Length (mm)	Part key	Simplified	Threaded
4	iso4762-m2-5x4	STEP	STEP
5	iso4762-m2-5x5	STEP	STEP
6	iso4762-m2-5x6	STEP	STEP
8	iso4762-m2-5x8	STEP	STEP
10	iso4762-m2-5x10	STEP	STEP
12	iso4762-m2-5x12	STEP	STEP
16	iso4762-m2-5x16	STEP	STEP
20	iso4762-m2-5x20	STEP	STEP
25	iso4762-m2-5x25	STEP	STEP

Dimensions

Symbol	Name	min	nom	max	Modeled	Rule	Level
P	Thread pitch		0.45		0.45	nominal	L1
b	Thread length	17	17 ref		17	reference value	L1
dk	Head diameter, plain head	4.32		4.5	4.41	midpoint of min–max	L1
dk_knurled	Head diameter, knurled head			4.68	4.68	single limit (max), modeled at the limit	L1
da	Transition diameter			3.1	3.1	single limit (max), modeled at the limit	L1
ds	Shank diameter	2.36		2.5	2.43	midpoint of min–max	L1
e	Socket width across corners	2.303			2.303	single limit (min), modeled at the limit	L1
k	Head height	2.36		2.5	2.43	midpoint of min–max	L1
r	Underhead fillet radius	0.1		0.3	0.2	midpoint of min–max	L0 (max: one source)
s	Socket width across flats	2.02	2	2.08	2.05	midpoint of min–max	L1
t	Socket depth	1.1			1.1	single limit (min), modeled at the limit	L1
lf	Underhead fillet length			0.51	0.51	single limit (max), modeled at the limit	L0 (max: one source)
v	Head top chamfer or radius			0.25	0.25	single limit (max), modeled at the limit	L1
dw	Bearing face diameter	4.18			4.18	single limit (min), modeled at the limit	L1
w	Wall thickness	0.85			0.85	single limit (min), modeled at the limit	L1
P	Coarse thread pitch		0.45		0.45	nominal	L1
tap_drill	Tap drill diameter		2.05		2.05	nominal	L1
d1	Basic minor diameter		2.0128606		2.0128606	nominal	L1
ch_angle	Chamfered end angle			50	50	single limit (max), modeled at the limit	L2
dh_fine	Clearance hole, fine series		2.7		2.7	nominal	L1
dh_medium	Clearance hole, medium series		2.9		2.9	nominal	L1
dh_coarse	Clearance hole, coarse series		3.1		3.1	nominal	L1

Thread and holes

• Tap drill: 2.05 mm (method: d − P), L1, sources amesweb-tap-drill, rule-tap-drill.
• Clearance hole (ISO 273): close 2.7, normal 2.9, loose 3.1 mm (L1: fine, medium and coarse series (albany-clearance, wikipedia-de-clearance)).

Drawing

As a PDF: CC-ISO4762-SZ-M2.5.pdf.

Goes with the M2.5 socket head cap screw

• Hex key: 2 mm, the socket's nominal width across flats (s) in the table above.
• ISO 4032 hex nut, the same size as this M2.5 socket head cap screw: M2.5 Hex Nut (Hexagon Nut), ISO 4032 / DIN 934
• ISO 7089 flat washer, the same size as this M2.5 socket head cap screw: M2.5 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)
4	0.345
5	0.375
6	0.405
8	0.465
10	0.525
12	0.585
16	0.705
20	0.825
25	0.975

The M2.5 socket head cap screw beside the M2 and the M3

The M2.5 is number 2, counting from the smallest, of the 7 ISO 4762 socket head cap screws published here, from M2 to M8.

• Thread pitch (P): 0.45 mm on the M2.5 socket head cap screw, against 0.4 mm on the M2 and 0.5 mm on the M3.
• Thread length (b): at least 17 mm on the M2.5 socket head cap screw, against at least 16 mm on the M2 and at least 18 mm on the M3.
• Head diameter, plain head (dk): 4.32 to 4.5 mm on the M2.5 socket head cap screw, against 3.62 to 3.8 mm on the M2 and 5.32 to 5.5 mm on the M3.
• Head diameter, knurled head (dk_knurled): up to 4.68 mm on the M2.5 socket head cap screw, against up to 3.98 mm on the M2 and up to 5.68 mm on the M3.
• Transition diameter (da): up to 3.1 mm on the M2.5 socket head cap screw, against up to 2.6 mm on the M2 and up to 3.6 mm on the M3.
• Shank diameter (ds): 2.36 to 2.5 mm on the M2.5 socket head cap screw, against 1.86 to 2 mm on the M2 and 2.86 to 3 mm on the M3.
• Socket width across corners (e): at least 2.303 mm on the M2.5 socket head cap screw, against at least 1.733 mm on the M2 and at least 2.873 mm on the M3.
• Head height (k): 2.36 to 2.5 mm on the M2.5 socket head cap screw, against 1.86 to 2 mm on the M2 and 2.86 to 3 mm on the M3.

Other sizes

• One size smaller: M2 Socket Head Cap Screw (Allen Bolt), ISO 4762 / DIN 912, 3.62 to 3.8 mm head, 1.5 mm hex key.
• One size larger: M3 Socket Head Cap Screw (Allen Bolt), ISO 4762 / DIN 912, 5.32 to 5.5 mm head, 2.5 mm hex key.

Documents

• CC-ISO4762-DS-M2.5.pdf: M2.5 datasheet: values with levels, lengths, sources
• CC-ISO4762-SZ-M2.5.pdf: M2.5 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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