ISO 898-1 Fastener Mechanical Properties
ISO 898-1 specifies the mechanical and physical properties of carbon steel and alloy steel bolts, screws and studs with specified property classes. The standard covers fasteners with metric coarse and fine pitch threads and provides a common classification system for different levels of strength and mechanical performance. It is widely referenced for industrial, machinery, construction and other applications where the strength of a threaded fastener needs to be clearly defined.
The property class, such as 4.8, 5.8, 6.8, 8.8, 9.8, 10.9 or 12.9, identifies the specified mechanical performance of the fastener rather than its dimensional design. We manufacture carbon steel and alloy steel fasteners in commonly required ISO 898-1 property classes, with controlled forming, heat treatment and testing processes to meet the applicable mechanical and physical requirements.
| Mechanical or physical property | Property class | ||||||||
| 4.6 | 4.8 | 5.6 | 6.8 | 8.8 (d≤16mm) | 8.8(d＞16mm) | 10.9 | 12.9 | ||
| Tensile strength, Rm, MPa | nom. | 400 | 400 | 500 | 600 | 800 | 800 | 1000 | 1200 |
| min. | 400 | 420 | 500 | 600 | 800 | 830 | 1040 | 1220 | |
| Lower yield strength, ReL d, MPa | nom. | 240 | - | 300 | - | - | - | - | - |
| min. | 240 | - | 300 | - | - | - | - | - | |
| Stress at 0,2 % nonproportional elongation, R p0,2, MPa | nom. | - | - | - | - | 640 | 640 | 900 | 1080 |
| min. | - | - | - | - | 640 | 660 | 940 | 1100 | |
| Percentage elongation after fracture for machined test pieces, A, % | min. | 22 | - | 20 | - | 12 | 12 | 10 | 8 |
| Percentage reduction of area after fracture for machined test pieces, Z, % | min. | - | 52 | 48 | 44 | ||||
| Vickers hardness, HV F W 98 N | min. | 120 | 130 | 155 | 190 | 250 | 255 | 320 | 385 |
| max. | 220 | 320 | 335 | 380 | 435 | ||||
| Rockwell hardness, HRC | min. | - | - | - | - | 22 | 23 | 32 | 39 |
| max. | - | - | - | - | 32 | 34 | 39 | 44 | |
Select fasteners with appropriate mechanical properties for the specific application to ensure safety and reliability. These properties may vary depending on factors like material, size, and manufacturing processes.
Material Chemical Composition:
ISO 898-1 fasteners are manufactured from carbon steel or alloy steel selected according to the required property class and fastener diameter. Chemical composition and heat treatment are controlled to achieve the specified mechanical properties. The table below summarizes commonly used steel grades, key alloying elements and typical heat treatment conditions for different fastener property classes. Actual material selection and heat treatment parameters may vary according to the steel grade, diameter and manufacturing process.
| Property Class | Material | Heat Treament | C(min) | C(max) | P(max) | S(max) | B(max) | Tempering temperature(℃） |
|---|---|---|---|---|---|---|---|---|
| 4.6 | Carbon steel or carbon steel with additives | / | - | 0.55 | 0.05 | 0.06 | Not Specified | - |
| 4.8 | - | 0.55 | 0.05 | 0.06 | ||||
| 5.6 | 0.13 | 0.55 | 0.05 | 0.06 | ||||
| 5.8 | - | 0.55 | 0.05 | 0.06 | ||||
| 6.8 | 0.15 | 0.55 | 0.05 | 0.06 | ||||
| 8.8 | Carbon steel with additives (e.g. Boron or Mn or Cr) | quenched and tempered | 0.15 | 0.4 | 0.025 | 0.025 | 0.03 | 425 |
| Carbon steel | quenched and tempered | 0.25 | 0.55 | 0.025 | 0.025 | |||
| Alloy steel | quenched and tempered | 0.2 | 0.55 | 0.025 | 0.025 | |||
| 10.9 | Carbon steel with additives (e.g. Boron or Mn or Cr) | quenched and tempered | 0.2 | 0.55 | 0.025 | 0.025 | 0.03 | 425 |
| Carbon steel | quenched and tempered | 0.25 | 0.55 | 0.025 | 0.025 | |||
| Alloy steel | quenched and tempered | 0.2 | 0.55 | 0.025 | 0.025 | |||
| 12.9 | Alloy steel | quenched and tempered | 0.3 | 0.5 | 0.025 | 0.025 | 0.03 | 425 |
| 12.9 | Carbon steel with additives (e.g. Boron or Mn or Cr) | quenched and tempered | 0.28 | 0.5 | 0.025 | 0.025 | 0.03 | 380 |
Proof loads:
Proof load is an important mechanical property specified by ISO 898-1 for carbon and alloy steel bolts, screws and studs. It represents the specified test load that a fastener must withstand without unacceptable permanent deformation. The required proof load depends on the fastener property class and the nominal stress area of the thread. Since coarse and fine pitch threads have different stress areas for the same nominal diameter, ISO 898-1 provides separate proof load values for coarse and fine pitch metric threads.
The following tables provide the minimum proof loads for the applicable ISO 898-1 property classes and thread sizes. These values can be used as a reference when selecting and verifying fasteners for applications requiring a specified mechanical performance.
ISO metric coarse pitch thread
The following table provides the proof loads specified for ISO metric coarse pitch threads according to ISO 898-1. Proof load is the specified test load that a fastener must withstand without unacceptable permanent deformation. The required proof load varies according to the nominal diameter, stress area and property class.
| Thread | Nominal stress area (mm2) | Proof Load(N) | ||||||||
| Class4.6 | Class4.8 | Class5.6 | Class5.8 | Class6.8 | Class8.8 | Class9.8 | Class10.9 | Class12.9 | ||
| M3 M3,5 M4 | 5,03 6,78 8,78 | 1 130 1 530 1 980 | 1 560 2 100 2 720 | 1 410 1 900 2 460 | 1 910 2 580 3 340 | 2 210 2 980 3 860 | 2 920 3 940 5 100 | 3 270 4 410 5 710 | 4 180 5 630 7 290 | 4 880 6 580 8 520 |
| M5 M6 M7 | 14,2 20,1 28,9 | 3 200 4 520 6 500 | 4 400 6 230 8 960 | 3 980 5 630 8 090 | 5 400 7 640 11 000 | 6 250 8 840 12 700 | 8 230 11 600 16 800 | 9 230 13 100 18 800 | 11 800 16 700 24 000 | 13 800 19 500 28 000 |
| M8 M10 M12 | 36,6 58 84,3 | 8 240 c 13 000 c 19 000 | 11 400 18 000 26 100 | 10 200 c 16 200 c 23 600 | 13 900 22 000 32 000 | 16 100 25 500 37 100 | 21 200 c 33 700 c 48 900 d | 23 800 37 700 54 800 | 30 400 c 48 100 c 70 000 | 35 500 56 300 81 800 |
| M14 M16 M18 | 115 157 192 | 25 900 35 300 43 200 | 35 600 48 700 59 500 | 32 200 44 000 53 800 | 43 700 59 700 73 000 | 50 600 69 100 84 500 | 66 700 d 91 000 d 115 000 | 74 800 102 000 — | 95 500 130 000 159 000 | 112 000 152 000 186 000 |
| M20 M22 M24 | 245 303 353 | 55 100 68 200 79 400 | 76 000 93 900 109 000 | 68 600 84 800 98 800 | 93 100 115 000 134 000 | 108 000 133 000 155 000 | 147 000 182 000 212 000 | — — — | 203 000 252 000 293 000 | 238 000 294 000 342 000 |
| M27 M30 M33 | 459 561 694 | 103 000 126 000 156 000 | 142 000 174 000 215 000 | 128 000 157 000 194 000 | 174 000 213 000 264 000 | 202 000 247 000 305 000 | 275 000 337 000 416 000 | — — — | 381 000 466 000 576 000 | 445 000 544 000 673 000 |
| M36 M39 | 817 976 | 184 000 220 000 | 253 000 303 000 | 229 000 273 000 | 310 000 371 000 | 359 000 429 000 | 490 000 586 000 | — — | 678 000 810 000 | 792 000 947 000 |
ISO metric fine pitch thread
The following table provides the proof loads specified for ISO metric fine pitch threads according to ISO 898-1. Fine pitch threads have a larger nominal stress area than coarse pitch threads of the same nominal diameter, resulting in different proof load values for the applicable property classes. The required proof load is determined by the nominal stress area and property class of the fastener.
| Thread | Nominal stress area (mm2) | Proof Load(N) | ||||||||
| Class4.6 | Class4.8 | Class5.6 | Class5.8 | Class6.8 | Class8.8 | Class9.8 | Class10.9 | Class12.9 | ||
| M8 × 1 M10 × 1,25 M10 × 1 | 39,2 61,2 64,5 | 8 820 13 800 14 500 | 12 200 19 000 20 000 | 11 000 17 100 18 100 | 14 900 23 300 24 500 | 17 200 26 900 28 400 | 22 700 35 500 37 400 | 25 500 39 800 41 900 | 32 500 50 800 53 500 | 38 000 59 400 62 700 |
| M12 × 1,5 M12 × 1,25 M14 × 1,5 | 88,1 92,1 125 | 19 800 20 700 28 100 | 27 300 28 600 38 800 | 24 700 25 800 35 000 | 33 500 35 000 47 500 | 38 800 40 500 55 000 | 51 100 53 400 72 500 | 57 300 59 900 81 200 | 73 100 76 400 104 000 | 85 500 89 300 121 000 |
| M16 × 1,5 M18 × 1,5 | 167 216 | 37 600 48 600 | 51 800 67 000 | 46 800 60 500 | 63 500 82 100 | 73 500 95 000 | 96 900 130 000 | 109 000 — | 139 000 179 000 | 162 000 210 000 |
| M20 × 1,5 M22 × 1,5 M24 × 2 | 272 333 384 | 61 200 74 900 86 400 | 84 300 103 000 119 000 | 76 200 93 200 108 000 | 103 000 126 000 146 000 | 120 000 146 000 169 000 | 163 000 200 000 230 000 | — — — | 226 000 276 000 319 000 | 264 000 323 000 372 000 |
| M27 × 2 M30 × 2 M33 × 2 | 496 621 761 | 112 000 140 000 171 000 | 154 000 192 000 236 000 | 139 000 174 000 213 000 | 188 000 236 000 289 000 | 218 000 273 000 335 000 | 298 000 373 000 457 000 | — — — | 412 000 515 000 632 000 | 481 000 602 000 738 000 |
| M36 × 3 M39 × 3 | 865 1 030 | 195 000 232 000 | 268 000 319 000 | 242 000 288 000 | 329 000 391 000 | 381 000 453 000 | 519 000 618 000 | — — | 718 000 855 000 | 839 000 999 000 |
Bolts Available with ISO 898-1 Mechanical Properties:
We manufacture a range of metric bolts that can be supplied with mechanical properties according to the applicable product and performance standards. The product range includes standard hexagon bolts, flange bolts and structural bolting products, with different strength classes available according to the relevant specifications.
Hexagon Bolts
DIN 931, DIN 933, ISO 4014 and ISO 4017 hexagon bolts can be supplied in commonly specified ISO 898-1 property classes, including 8.8, 10.9 and 12.9. These standards define the dimensional and product requirements, while the applicable mechanical property class is specified separately.
Heavy Hex Structural Bolts
DIN 6914 and EN 14399-3/EN 14399-4 structural bolts are designed for high-strength structural bolted connections. These products are supplied according to the specific requirements of the applicable structural bolting standards, including dimensional, mechanical and assembly requirements.
Flange Bolts
DIN 6921 flange bolts can be manufactured in different material and strength grades according to the applicable product and mechanical property requirements. The integrated flange provides a larger bearing surface and makes these bolts suitable for mechanical and industrial assemblies where efficient fastening is required.
Threaded Rods
DIN 975 threaded rods are available in a range of metric thread sizes and lengths for applications requiring continuous external threads. Carbon steel and alloy steel options can be supplied in different strength classes according to the applicable specification, including commonly requested grades used with ISO 898-1 mechanical property requirements. Surface finishes such as plain, zinc plated and other specified coatings can also be provided.
Stud Bolts
DIN 976 stud bolts are manufactured with external threads along the specified length and are commonly used where a threaded fastening element is installed between two components, such as in machinery and equipment assemblies. Depending on the specified material and property class, DIN 976 stud bolts can be supplied with mechanical properties according to the applicable requirements, including ISO 898-1 where specified.