DIN 6921 Hexagon Flange Bolt

The German standard DIN 6921 covers hexagon head bolts with a flange (serrated washer). The shank may be fully or partially threaded. Based on the texture of the underside of the flange, there are two types of these fasteners:

• with a smooth finish;
• with locking serrations or teeth.

A DIN 6921 bolt with serrations on the flange is called self-locking, as it increases the grip force against the mating surface, thereby preventing the fastener from loosening. In addition, the serrated washer protects the seating surface from damage by increasing the bearing area.

This feature is especially useful when joining thin parts. Using this design eliminates the need for auxiliary washers and speeds up assembly of the fastening joint.

Materials and applications of DIN 6921 bolts

Depending on the raw material used, several variants of this fastener group are produced, made of:

• alloy steel with property class 8.8, 10.9, 12.9 in plain black finish, oxidized, or with yellow or white zinc electroplating;
• austenitic stainless steel grade A2 and A4 with enhanced acid resistance.

The DIN 6921 standard has equivalents: European standards EN 1665 and EN 14219, as well as international documents ISO 8100 and ISO 8102. Fasteners meeting the requirements of these standards are used in construction, mechanical and instrument engineering, and shipbuilding.

They are used for secure connections in structures whose joints are subjected to high operational dynamic loads. Hexagon flange bolts made of austenitic steel A4 withstand exposure to acids, alkalis and seawater.

Choosing hexagon flange bolts

Products manufactured to different standards may differ in ways that affect the performance of the fastened joint. Before purchasing fasteners, we recommend consulting FLOK specialists.

FLOK supplies hexagon flange bolts DIN 6921 wholesale and retail, in any assortment, with delivery across Russia.

Dimensions and parameters table for DIN 6921 flange bolts, mm

d		M5	M6	M8	M10	M12	M14	M16
P		0.8	1	1.25	1.5	1.75	2	2
k	DIN 6921	5.4	6.6	8.1	9.2	11.5	12.8	14.4
	EN 1665				10.4	11.8	13.7	15.4
S	DIN 6921	8	10	13	15	16	18	21
	EN 1665				16	18	21	24
d₂		9.8	12.2	15.8	19.6	23.8	27.6	31.9
b	l ≤ 125	16	18	22	26	30	34	38
	125 < l ≤ 200	-	-	28	32	36	40	44
	l > 200	-	-	-	-	-	-	57

Designations:

d - nominal thread diameter

P - thread pitch

k - bolt head height, max.

S - width across flats

d₂ - flange diameter, min.

b - length of the threaded part

l - bolt length

Head dimensions table for DIN 6921 flange bolts

k	5.5	7	7.9	11	14.4
s	10	13	15	17	21
d2	14.5	18.3	21	26	35

Dimensions table for DIN 6921 flange bolts

L (mm)	d
	M6	M8	M10	M12	M16
10
12
16
20
25
30
35
40