Din931 Hex Bolt Description
DIN931 hex bolt, also known as external hex bolt, is a fastener composed of a hex head and a threaded rod with external threads. It is usually used with a nut and is commonly used to fasten and connect two parts with through-holes. DIN931 hex bolt is a half-threaded bolt, with part of the threaded rod and part of the smooth rod, and is divided into A grade and B grade. As shown in the figure, here is a set of stainless steel DIN931 hex bolts:
Available Surface Treatment
Whitening
Hot Dip Galvanized
Darcromet
Black
Blue White Zinc
Colored Zinc
Din931 Hex Bolt Mark
Hexagon bolts must be marked with the manufacturer’s identification mark and performance grade mark. It is best to mark them with raised or recessed letters on the top surface of the head or with recessed letters on the side surface of the head. All performance grades of external hexagon bolts must be marked, and the marking for stainless steel external hexagon bolts should also include the steel group, as in the example shown in the figure above, where the stainless steel external hexagon bolt is marked A4-70 on the top surface of the head.
DIN931 Hex Bolt Production Mark and Thread Size:
Production Mark:
The manufacturer’s identification mark and grade level mark must be clearly marked on the top or side of the hex head using raised or recessed characters for external hex bolts. This marking is required for all performance grades of external hex bolts, and for stainless steel external hex bolts, the marking should also include the steel group, such as A4-70 in the example shown in the previous image.
DIN931 Hex Bolts Size:
DIN931 hex bolts reference the German standard DIN931-1987, which specifies thread sizes ranging from M1.6 to M39 and product grades of A and B for hex head bolts. The drawing of DIN931 external hex bolts is shown in this image.
DIN931 Hex Bolt Specification:
| Thread specification d | Pitch P | b | C | da | dw | ds | k | the s | e | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| A | B | A | B | A | B | Nominal size | A | B | A | B | ||||||||||
| L≤125mm | 125<L≤200mm | L>200mm | min | max | max | min | min | min | max | min | max | min | min | |||||||
| M1.6 | 0.35 | 9 | – | – | 0.1 | 0.25 | 2 | 2.4 | – | 1.46 | – | 0.98 | 1.22 | – | – | 3.2 | 3.02 | – | 3.41 | – |
| M2 | 0.4 | 10 | – | – | 0.1 | 0.25 | 2.6 | 3.2 | – | 1.86 | – | 1.28 | 1.52 | – | – | 4 | 3.82 | – | 4.32 | – |
| M2.5 | 0.45 | 11 | – | – | 0.1 | 0.25 | 3.1 | 4.1 | – | 2.36 | – | 1.58 | 1.82 | – | – | 5 | 4.82 | – | 5.45 | – |
| M3 | 0.5 | 12 | – | – | 0.15 | 0.4 | 3.6 | 4.6 | – | 2.86 | – | 1.88 | 2.12 | – | – | 5.5 | 5.32 | – | 6.01 | – |
| M3.5 | 0.6 | 13 | – | – | 0.15 | 0.4 | 4.1 | 5.1 | – | 3.32 | – | 2.28 | 2.52 | – | – | 6 | 5.82 | – | 6.58 | – |
| M4 | 0.7 | 14 | – | – | 0.15 | 0.4 | 4.7 | 5.9 | – | 3.82 | – | 2.68 | 2.92 | – | – | 7 | 6.78 | – | 7.66 | – |
| M5 | 0.8 | 16 | 22 | – | 0.15 | 0.5 | 5.7 | 6.9 | – | 4.82 | – | 3.35 | 3.65 | – | – | 8 | 7.78 | – | 8.79 | – |
| M6 | 1 | 18 | 24 | – | 0.15 | 0.5 | 6.8 | 8.9 | – | 5.82 | – | 3.85 | 4.15 | – | – | 10 | 9.78 | – | 11.05 | – |
| M7 | 1 | 20 | 26 | – | 0.15 | 0.5 | 7.8 | 9.6 | – | 6.78 | – | 4.65 | 4.95 | – | – | 11 | 10.73 | – | 12.12 | – |
| M8 | 1.25 | 22 | 28 | – | 0.15 | 0.6 | 9.2 | 11.6 | – | 7.78 | – | 5.15 | 5.45 | – | – | 13 | 12.73 | – | 14.38 | – |
| M10 | 1.5 | 26 | 32 | 45 | 0.15 | 0.6 | 11.2 | 15.6 | – | 9.78 | – | 6.22 | 6.58 | – | – | 17 | 16.73 | – | 18.9 | – |
| M12 | 1.75 | 30 | 36 | 49 | 0.15 | 0.6 | 13.7 | 17.4 | – | 11.7 | – | 7.32 | 7.68 | – | – | 19 | 18.67 | – | 21.1 | – |
| M14 | 2 | 34 | 40 | 53 | 0.15 | 0.6 | 15.7 | 20.5 | – | 13.7 | – | 8.62 | 8.98 | – | – | 22 | 21.67 | – | 24.49 | – |
| M16 | 2 | 38 | 44 | 57 | 0.2 | 0.8 | 17.7 | 22.5 | 22 | 15.7 | 15.6 | 9.82 | 10.2 | 9.71 | 10.3 | 24 | 23.67 | 23.16 | 26.75 | 26.17 |
| M18 | 2.5 | 42 | 48 | 61 | 0.2 | 0.8 | 20.2 | 25.3 | 24.8 | 17.7 | 17.6 | 11.3 | 11.7 | 11.2 | 11.9 | 27 | 26.67 | 26.16 | 30.14 | 29.56 |
| M20 | 2.5 | 46 | 52 | 65 | 0.2 | 0.8 | 22.4 | 28.2 | 27.7 | 19.7 | 19.5 | 12.3 | 12.7 | 12.2 | 12.9 | 30 | 29.67 | 29.16 | 33.53 | 32.95 |
| M22 | 2.5 | 50 | 56 | 69 | 0.2 | 0.8 | 24.4 | 30 | 29.5 | 21.7 | 21.5 | 13.8 | 14.2 | 13.7 | 14.4 | 32 | 31.61 | 31 | 35.72 | 35.03 |
| M24 | 3 | 54 | 60 | 73 | 0.2 | 0.8 | 26.4 | 33.6 | 33.2 | 23.7 | 23.5 | 14.8 | 15.2 | 14.7 | 15.4 | 36 | 35.38 | 35 | 39.98 | 39.55 |
| M27 | 3 | 60 | 66 | 79 | 0.2 | 0.8 | 30.4 | – | 38 | 26.5 | – | – | 16.7 | 17.4 | 41 | – | 40 | – | 45.2 | |
| M30 | 3.5 | 66 | 72 | 85 | 0.2 | 0.8 | 33.4 | – | 42.7 | 29.5 | – | – | 18.3 | 19.1 | 46 | – | 45 | – | 50.85 | |
| M33 | 3.5 | 72 | 78 | 91 | 0.2 | 0.8 | 36.4 | – | 46.6 | 32.4 | – | – | 20.6 | 21.4 | 50 | – | 49 | – | 55.37 | |
| M36 | 4 | 78 | 84 | 97 | 0.2 | 0.8 | 39.4 | – | 51.1 | 35.4 | – | – | 22.1 | 22.9 | 55 | – | 53.8 | – | 60.79 | |
| M39 | 4 | 84 | 90 | 103 | 0.3 | 1 | 42.4 | – | 55.9 | 38.4 | – | – | 24.6 | 25.4 | 60 | – | 58.8 | – | 66.44 | |
DIN931 Hex Bolt Material Chemical Composition:
DIN931 hex bolts are made of carbon steel and stainless steel. The strength level of carbon steel hex bolts is divided into 5.6 grade, 8.8 grade, and 10.9 grade.
The chemical composition of each grade of carbon steel hex bolts is shown below:
| Strength Level | Material | heat treatment | chemical composition% | tempering temperature | ||||
|---|---|---|---|---|---|---|---|---|
| C | P | S | B | ℃ | ||||
| min | max | max | max | max | min | |||
| 5.6 | carbon steel | – | 0.13 | 0.55 | 0.05 | 0.06 | 0.003 | – |
| 8.8 | low carbon alloy steel | quenched and tempered | 0.15 | 0.04 | 0.035 | 0.035 | 0.003 | 425 |
| Carbon steel | 0.25 | 0.55 | 0.035 | 0.035 | 0.003 | |||
| 10.9 | low carbon alloy steel | quenched and tempered | 0.15 | 0.35 | 0.035 | 0.035 | 0.003 | 340 |
| Carbon steel | 0.25 | 0.55 | 0.035 | 0.035 | 0.003 | 425 | ||
| Medium Carbon Alloy Steel | 0.2 | 0.55 | 0.035 | 0.035 | 0.003 | |||
| alloy steel | 0.2 | 0.55 | 0.035 | 0.035 | 0.003 | |||
DIN931 hexagonal bolts are available in stainless steel A2-70, A4-70 and A4-80, with complete specifications and quality assurance
Carbon Steel DIN931 Hexagonal Bolt Mechanical Property:
| Material | Strength Level | Nominal Tensile Strength | Minimum tensile strength | Vickers hardness HV | Brinell hardness HB | Rockwell hardness HR | Yield point | guaranteed stress | Specified non-proportional elongation stress | elongation after break | rate of reduction in area | Impact absorption energy | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| min | max | min | max | min | max | Nominal | min | Nominal | min | |||||||||
| carbon steel | 5.6 | 500 | 500 | 155 | 220 | 147 | 209 | 79 | 95 | 300 | 300 | 280 | – | – | 20 | – | 25 | |
| 8.8 | d≤16mm | 800 | 800 | 250 | 320 | 238 | 304 | twenty two | 32 | – | – | 580 | 640 | 640 | 12 | 52 | 30 | |
| d>16mm | 800 | 830 | 255 | 335 | 242 | 318 | twenty three | 34 | – | – | 600 | 640 | 660 | 12 | 52 | 30 | ||
| 10.9 | 1000 | 1040 | 320 | 380 | 304 | 361 | 32 | 39 | – | – | 830 | 900 | 940 | 9 | 48 | 20 | ||
Stainless Steel Din931 Hex Bolt Mechanical Property:
The mechanical properties of stainless steel DIN931 hex bolts are shown in the table below. The wedge load strength of hex bolts made of austenitic stainless steel should not be less than the minimum tensile strength value in the table below.
| material | category | group | Strength Level | thread diameter | tensile strength | Specified non-proportional elongation stress | elongation after break | hardness | ||
|---|---|---|---|---|---|---|---|---|---|---|
| HB | HRC | HV | ||||||||
| Stainless steel | Austenitic | A2、A4 | 50 | ≤M39 | 500 | 210 | 0.6d | – | – | – |
| 70 | ≤M24 | 700 | 450 | 0.4d | – | – | – | |||
| 80 | ≤M24 | 800 | 600 | 0.3d | – | – | – | |||
| martensite | C3 | 80 | – | 800 | 640 | 0.2d | 228-323 | 21-35 | 240-340 | |
| C4 | 50 | – | 500 | 250 | 0.2d | 147-209 | – | 155-220 | ||
| 70 | – | 700 | 410 | 0.2d | 209-314 | 20-34 | 220-330 | |||
DIN931 hex bolts come in both coarse and fine thread variants, and the minimum tensile load and guaranteed load for each variant differ.
Minimum Tensile Load and Guaranteed Load for DIN931 Hex Bolt – Coarse Thread
| Thread specification | Stress cross-sectional area of thread | Minimum tensile load (As×σbmin) /N | Guaranteed load (As×Sp) /N | ||||
|---|---|---|---|---|---|---|---|
| Strength Level | |||||||
| d | As/mm2 | 5.6 | 8.8 | 10.9 | 5.6 | 8.8 | 10.9 |
| M3 | 5.03 | 2 510 | 4 020 | 5 230 | 1 410 | 2 920 | 4 180 |
| M3.5 | 6.78 | 3 390 | 5 420 | 7 050 | 1 900 | 3 940 | 5 630 |
| M4 | 8.78 | 4 390 | 7 020 | 9 130 | 2 460 | 5 100 | 7 290 |
| M5 | 14.2 | 7 100 | 11 350 | 14 800 | 3 980 | 8 230 | 11 800 |
| M6 | 20.1 | 10 000 | 16 100 | 20 900 | 5 630 | 11 600 | 16 700 |
| M7 | 28.9 | 14 400 | 23 100 | 30 100 | 8 090 | 16 800 | 24 000 |
| M8 | 36.6 | 18 300 | 29 200 | 38 100 | 10 200 | 21 200 | 30 400 |
| M10 | 58 | 29 000 | 46 400 | 60 300 | 16 200 | 33 700 | 48 100 |
| M12 | 84.3 | 42 200 | 67 400 | 87 700 | 23 600 | 48 900 | 70 000 |
| M14 | 115 | 57 500 | 92 000 | 120 000 | 32 200 | 66 700 | 95 500 |
| M16 | 157 | 78 500 | 125 000 | 163 000 | 44 000 | 91 000 | 130 000 |
| M18 | 192 | 96 000 | 159 000 | 200 000 | 53 800 | 115 000 | 159 000 |
| M20 | 245 | 122 000 | 203 000 | 255 000 | 68 600 | 147 000 | 203 000 |
| M22 | 303 | 152 000 | 252 000 | 315 000 | 84 800 | 182 000 | 252 000 |
| M24 | 353 | 176 000 | 293 000 | 367 000 | 98 800 | 212 000 | 293 000 |
| M27 | 459 | 230 000 | 381 000 | 477 000 | 128 000 | 275 000 | 381 000 |
| M30 | 561 | 280 000 | 466 000 | 583 000 | 157 000 | 337 000 | 466 000 |
| M33 | 694 | 347 000 | 576 000 | 722 000 | 194 000 | 416 000 | 576 000 |
| M36 | 817 | 408 000 | 678 000 | 850 000 | 229 000 | 490 000 | 678 000 |
| M39 | 976 | 488 000 | 810 000 | 1 020 000 | 273 000 | 586 000 | 810 000 |
The minimum tensile load and guaranteed load of DIN931 hex bolts – Fine Threads:
| Thread specification dxp | Stress cross-sectional area of thread | Minimum tensile load (As×σbmin) /N | Guaranteed load (As×Sp) /N | ||||
|---|---|---|---|---|---|---|---|
| Strength Level | |||||||
| As/mm2 | 5.6 | 8.8 | 10.9 | 5.6 | 8.8 | 10.9 | |
| M8X1 | 39.2 | 19600 | 31360 | 40800 | 11 000 | 22 700 | 32 500 |
| M10X1 | 64.5 | 32300 | 51600 | 67100 | 18 100 | 37 400 | 53 500 |
| M10X1.25 | 61.2 | 30600 | 49000 | 63600 | 17 100 | 35 500 | 50 800 |
| M12X1.25 | 92.1 | 46100 | 73700 | 95800 | 25 800 | 53 400 | 76 400 |
| M12X1.5 | 88.1 | 44100 | 70500 | 91600 | 24 700 | 51 100 | 73 100 |
| M14X1.5 | 125 | 62500 | 100000 | 130000 | 35 000 | 72 500 | 104 000 |
| M16X1.5 | 167 | 83500 | 134000 | 174000 | 46 800 | 96 900 | 139 000 |
| M18X1.5 | 216 | 108000 | 179000 | 225000 | 60 500 | 130 000 | 179 000 |
| M20X1.5 | 272 | 136000 | 226000 | 283000 | 76 200 | 163 000 | 226 000 |
| M22X1.5 | 333 | 166000 | 276000 | 346000 | 93 200 | 200 000 | 276 000 |
| M24X2 | 384 | 192000 | 319000 | 399000 | 108 000 | 230 000 | 319 000 |
| M27X2 | 496 | 248000 | 412000 | 516000 | 139 000 | 298 000 | 412 000 |
| M30X2 | 621 | 310000 | 515000 | 646000 | 174 000 | 373 000 | 515 000 |
| M33X2 | 761 | 380000 | 632000 | 791000 | 213 000 | 457 000 | 632 000 |
| M36X3 | 865 | 432000 | 718000 | 900000 | 242 000 | 519 000 | 718 000 |
| M39X3 | 1030 | 515000 | 855000 | 1070000 | 288 000 | 618 000 | 855 000 |
DIN 931 Hex Bolt Application
DIN931 hex bolts with coarse and fine threads are commonly used with nuts to connect two parts into a whole using threaded connections, which belong to detachable connections. The minimum tensile load and guaranteed load for coarse and fine thread hex bolts are different. Fine thread hex bolts have better self-locking performance than coarse thread bolts and are often used in parts subjected to large impact shocks or alternating loads, or in adjusting mechanisms.
When using hex bolts, it is important to prevent loosening to avoid accidents and disruption of normal operations. Methods of preventing loosening include friction prevention, mechanical prevention, and other measures. Hex bolts are widely used in various industries such as machinery, electronics, communication equipment, furniture, and construction for production, installation, and maintenance due to their simple assembly, easy disassembly, high efficiency, and broad applications.
