DIN 931 Bolt with Partial Thread

The German standard DIN 931 covers a universal hex head bolt with a wrench-fit head and a partial metric thread on the shank. The thread diameter ranges from M1.6 to M64. The length of product grade A bolts reaches 150 mm, and of product grade B bolts — 200 mm. The simple design and high strength define the application areas: industry, construction, furniture manufacturing and other sectors.

Manufacturing features: standard requirements and materials

The German standard DIN 931 is similar to the international standards ISO 4014 and ISO 4016, but there are differences in product grades. The full Russian equivalent for product grade A is GOST 7805-70, for product grade B — GOST 7798-70, for product grade C — GOST 15589-70. When selecting an equivalent, accuracy, dimensions and materials must be taken into account, as they determine the possible applications. The bolt differs from the international standard EN ISO 4017 in having a partial thread.

The DIN 931 bolt has a hexagon head that is convenient for tightening and loosening with a wrench. The shank is fitted with a partial coarse-pitch metric thread, which ensures reliable fixation of the parts. The bolt is installed into a pre-drilled hole, threaded or unthreaded; in the latter case, nuts and washers are used for fastening.

Fasteners of this type are made from the following materials:

• Steel, property class 5.6, 8.8, 10.9, 12.9. The standard provides for the manufacture of high-strength bolts designed for heavy mechanical loads. They are used for critical connections of parts and assemblies; the high strength ensures the ability to withstand continuous mechanical stress.
• Steel with protective coating. Zinc, nickel or chrome coating is used for corrosion protection. It is applied by electroplating, dispersion or thermal diffusion methods, forming a durable protective film that shields the metal from aggressive environments and prevents corrosion.
• Stainless steel, grades A2-A5. Austenitic acid-resistant steels withstand prolonged exposure to aggressive environments and are not subject to corrosion.
• Brass and other non-ferrous metal alloys. Not subject to corrosion, unaffected by high humidity, with good decorative qualities.

Fastening bolts are also made from polymer materials. Various types of plastic are not subject to corrosive environmental effects and can be used in conditions of high humidity, direct sunlight, and temperature fluctuations.

Applications of fastening bolts

Fasteners of this type are versatile due to their simple design and ease of installation. The main application areas are:

• Industry: mechanical engineering, machine tool manufacturing, instrument making, assembly of automobiles, special-purpose vehicles and other machines and mechanisms. The fasteners provide a high-strength connection of parts.
• Construction. Fastening bolts are used in construction and installation work, in the assembly of metal frames and installation of profiles. A threaded connection remains one of the most reliable ways to join parts.
• Furniture manufacturing. Bolts are used to join components made of metal, plastic, wood, and wood-based panel materials — in the assembly of various types of furniture.

Fasteners are also used in repair, installation, finishing and other types of work.

DIN 931 size table

b (L<125)	16	18	22	26	30
b )(125<L<200	22	24	28	32	36
b(L>200)	-	-	-	45	49
k	3.5	4	5.3	6.4	7.5
s	8	10	13	17	19

L (mm)	d
	M5	M6	M8	M10	M12
30
35
40
45
50
55
60
65
70
75
80
90
100
110
120
130
140
150
160
180
200
220
240…320

b	34	38	46	54	60
dk (max)	40	44	52	60	66
f (max)	53	57	65	73	79
k (max)	8.8	10	12.5	15	17
v (max)	22	24	30	36	41

L (mm)	d
	M14	M16	M20	M24	M27
45
50
55
60
65
70
75
80
90
100
110
120
130
140
150
160

b	34	38	46	54	60
dk (max)	40	44	52	60	66
f (max)	53	57	65	73	79
k (max)	8.8	10	12.5	15	17
v (max)	22	24	30	36	41

L (mm)	d
	M14	M16	M20	M24	M27
180
200
220
240
260
280
300
320
360
380
400
420

b	66	78
dk (max)	72	84
f (max)	85	97
k (max)	18.7	22.5
v (max)	46	55

L (mm)	d
	M30	M36
80
90
100
110
120
130
140
150
160
180
200
220
240
260
280
300
320
360
380
400
420

Parameter	DIN 931	DIN 933
Thread position	partial thread	full thread along shank length
D - nominal thread diameter, mm	from M3 to M64	from M3 to M64
S - width across flats, mm	from 5.5 to 95	from 5.5 to 95
K - head height, mm	from 2 to 40	from 2 to 40
L - bolt length, mm	from 30 to 950	from 5 to 340
B - thread length, mm	from 12 to 153	along bolt length, excluding thread runout
A - thread runout, mm	-	from 1.5 to 18
Material, coating	Coated steel: zinc-plated, nickel-plated, chromate-plated. Stainless steel: A2 - A5, A2/A4-70, A2/A4-80. Brass, aluminium, copper alloy. Plastic	Coated steel: zinc-plated, nickel-plated, chromate-plated. Stainless steel: A2 - A5, A2/A4-70, A2/A4-80. Brass, aluminium, copper alloy. Plastic
Property class	5.6, 8.8, 10.9, 12.9, 1.7709, 1.7218	5.6, 8.8, 10.9, 12.9, 1.7709, 1.7218
Product grade	A, B	A, B