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ISO 898-2 Specification

Hex Nuts, Hexagon High Nuts

ISO 898-2 Scope

ISO 898-2 specification concludes mechanical and physical properties of nuts with coarse thread and fine pitch thread made of carbon steel and alloy steel when tested at an ambient temperature range of 10 °C to 35 °C.
Thin Nuts, Regular Nuts & High Nuts conforming to the requirements of ISO 898-2 are evaluated at that ambient temperature range and used in applications ranging from -50 °C to +150 °C. ISO 898-2 specification is applicable for nuts with coarse thread M5 ≤ D ≤ M39, and fine pitch thread M8×1 ≤ D ≤ M39×3 in accordance with diameter/pitch combinations as per ISO 261 and ISO 262.

Related Specifications of ISO 898-2 Bolting

DIN 267 BS EN 1515 EN 10269 F2281 A320 SAE J429 SAE J995 ISO 898-1 ISO 898-3 ISO 898-5

ISO 898-2 Designations

Property class Range of nominal diameters, D
Regular nut (style 1) High nut (style 2) Thin nut (style 0)
04 - - M5 ≤ D ≤ M39 M8×1 ≤ D ≤ M39×3
05 - - M5 ≤ D ≤ M39 M8×1 ≤ D ≤ M39×3
5 M5 ≤ D ≤ M39 M8×1 ≤ D ≤ M39×3 - -
6 M5 ≤ D ≤ M39 M8×1 ≤ D ≤ M39×3 - -
8 M5 ≤ D ≤ M39 M8×1 ≤ D ≤ M39×3 M5 < D ≤ M39 M8×1 ≤ D ≤ M39×3 -
9 - M5 ≤ D ≤ M39 -
10 M5 ≤ D ≤ M39 M8×1 ≤ D ≤ M16×1,5 M5 ≤ D ≤ M39 M8×1 ≤ D ≤ M39×3 -
12 M5 ≤ D ≤ M16 M5 ≤ D ≤ M39 M8×1 ≤ D ≤ M16×1,5 -

ISO 898-2 Nut & Bolt Combinations

Nut property class Maximum property class of mating bolt, screw and stud
5 5.8
6 6.8
8 8.8
9 9.8
10 10.9
12 12.9/12.9

ISO 898-2 Chemical Composition

Thread Property class Material and nut heat treatment Chemical composition limit (cast analysis %)a
C max. Mn min. P max. S max.
Coarse thread 04c Carbon steeld 0,58 0,25 0,060 0,150
05c Carbon steel, QTe 0,58 0,30 0,048 0,058
5b Carbon steeld 0,58 - 0,060 0,150
6b Carbon steeld 0,58 - 0,060 0,150
8 High nut (style 2) Carbon steeld 0,58 0,25 0,060 0,150
8 Regular nut (style 1) D £ M16 Carbon steeld 0,58 0,25 0,060 0,150
8c Regular nut (style 1) D > M16 Carbon steel, QTe 0,58 0,30 0,048 0,058
9 Carbon steeld 0,58 0,25 0,060 0,150
10c Carbon steel, QTe 0,58 0,30 0,048 0,058
12c Carbon steel, QTe 0,58 0,45 0,048 0,058
Fine pitch thread 04b Carbon steeld 0,58 0,25 0,060 0,150
05c Carbon steel, QTe 0,58 0,30 0,048 0,058
5b Carbon steeld 0,58 - 0,060 0,150
6b D ≤ M16 Carbon steeld 0,58 - 0,060 0,150
6b D > M16 Carbon steel; QTe 0,58 0,30 0,048 0,058
8 High nut (style 2) Carbon steeld 0,58 0,25 0,060 0,150
8c Regular nut (style 1) Carbon steel, QTe 0,58 0,30 0,048 0,058
10c Carbon steel, QTe 0,58 0,30 0,048 0,058
12c Carbon steel, QTe 0,58 0,45 0,048 0,058
  • QT = Quenched and tempered nuts.
  • “-“ No limit specified.
  • a In case of dispute, the product analysis applies.
  • b Nuts of these property classes may be manufactured from free-cutting steel upon agreement between the purchaser and the manufacturer; in such a case, sulfur, phosphorus and lead are permissible with the following maximum contents: S: 0,34 %; P: 0,11 %; Pb: 0,35%.
  • c Alloying elements may be added, provided the mechanical properties required in Clause 7 are fulfilled.
  • d This may be quenched and tempered at the manufacturer’s discretion.
  • e For materials of these property classes, there shall be sufficient hardenability to ensure a structure consisting of approximately 90 % martensite in the “as-hardened” condition before tempering in the threaded area of the nut as specified

ISO 898-2 Mechanical Properties

Proof load values for nuts with coarse thread

Thread D Pitch P Proof load a, N Property class
04b 05 5 6 8 9 10 12
M5 0,8 5400 7100 8250 9500 12140 13000 14800 16300
M6 1 7640 10000 11700 13500 17200 18400 20900 23100
M7 1 11000 14500 16800 19400 24700 26400 30100 33200
M8 1,25 13900 18300 21600 24900 31800 34400 38100 42500
M10 1,5 22000 29000 34200 39400 50500 54500 60300 67300
M12 1,75 32000 42200 51400 59000 74200 80100 88500 100300
M14b 2 43700 57500 70200 80500 101200 109300 120800 136900
M16 2 59700 78500 95800 109900 138200 149200 164900 186800
M18 2,5 73000 96000 121000 138200 176600 176600 203500 230400
M20 2,5 93100 122500 154400 176400 225400 225400 259700 294000
M22 2,5 115100 151500 190900 218200 278800 278800 321200 363600
M24b 3 134100 176500 222400 254200 324800 324800 374200 423600
M27 3 174400 229500 289200 330500 422300 422300 486500 550800
M30 3,5 213200 280500 353400 403900 516100 516100 594700 673200
M33 3,5 263700 347000 437200 499700 638500 638500 735600 832800
M36 4b 310500 408500 514700 588200 751600 751600 866000 980400
M39 4b 370900 488000 614900 702700 897900 897900 1035000 1171000
  • a For the application of thin nuts, it should be considered that the stripping load is lower than the proof load of a nut with full loadability (see Annex A).

Proof load values for nuts with fine pitch thread

Thread D x P Proof load a, N Property class
04b 05 5 6 8 10 12
M8x1 14900 19600 27000 30200 37400 43100 47000
M10x1,25 23300 30600 44200 47100 58400 67300 73400
M10x1 24500 32200 44500 49700 61600 71000 77400
M12x1,5 33500 44000 60800 68700 84100 97800 105700
M12x1,25 35000 46000 63500 71800 88000 102200 110500
M14x1,5 47500 62500 86300 97500 119400 138800 150000
M16x1,5 63500 83500 115200 130300 159500 185400 200400
M18x2 77500 102000 146900 177500 210100 220300 -
M18x1,5 81700 107500 154800 187000 221500 232200 -
M20x2 98000 129000 185800 224500 265700 278600 -
M20x1,5 103400 136000 195800 236600 280200 293800 -
M22x2 120800 159000 229000 276700 327500 343400 -
M22x1,5 126500 166500 239800 289700 343000 359600 -
M24x2 145900 192000 276500 334100 395500 414700 -
M27x2 188500 248000 351100 431500 510900 535700 -
M30x2 236000 310500 447100 540300 639600 670700 -
M33x2 289200 380500 547900 662100 783800 821900 -
M36x3 328700 432500 622800 804400 942800 934200 -
M39x3 391400 515000 741600 957900 1123000 1112000 -
  • a For the application of thin nuts, it should be considered that the stripping load is lower than the proof load of a nut with full loadability, see Annex A

Hardness properties for nuts with coarse thread

Thread D Property class
04b 05 5 6 8 9 10 12
Vickers hardness, HV
min. max. min. max. min. max. min. max. min. max. min. max. min. max. min. max.
M5 ≤ D ≤ M16 188 302 272 353 130 302 150 302 200 302 188 302 272 353 295c 353
M16 < D ≤ M39 146 170 233a 353b 272
Brinell hardness, HB
min. max. min. max. min. max. min. max. min. max. min. max. min. max. min. max.
M5 ≤ D ≤ M16 179 287 259 336 124b 287 143 287 190 287 179 287 259 336 280c 336
M16 < D ≤ M39 139 162 221a 336b 259
Rockwell hardness, HRC
min. max. min. max. min. max. min. max. min. max. min. max. min. max. min. max.
M5 ≤ D ≤ M16 - 30 26 36 - 30 - 30 - 30 - 30 26 36 29c 36
M16 < D ≤ M39 - 36b 26
  • Surface integrity shall be in accordance with ISO 6157-2.
  • Vickers hardness test is the reference method for acceptance (see 9.2.4).
  • a Minimum value for high nuts (style 2): 180 HV (171 HB).
  • b Maximum value for high nuts (style 2): 302 HV (287 HB; 30 HRC).
  • c Minimum value for high nuts (style 2): 272 HV (259 HB; 26 HRC).

Hardness properties for nuts with fine pitch thread

Thread D x P Property class
04b 05 5 6 8 10 12
Vickers hardness, HV
min. max. min. max. min. max. min. max. min. max. min. max. min. max.
M8×1 ≤ D ≤ M16×1,5 188 302 272 353 175 302 188 302 250a 353b 295c 353 295 353
M16×1,5 < D ≤ M39×3 190 233 295 353 260 - -
Brinell hardness, HB
min. max. min. max. min. max. min. max. min. max. min. max. min. max.
M8×1 ≤ D ≤ M16×1,5 179 287 259 336 166 287 179 287 238a 336b 280c 336 280 336
M16×1,5 < D ≤ M39×3 181 221 280 336 247 - -
Rockwell hardness, HRC
min. max. min. max. min. max. min. max. min. max. min. max. min. max.
M8×1 ≤ D ≤ M16×1,5 - 30 26 36 - 30 - 30 22,2a 36b 29c 36 29 36
M16×1,5 < D ≤ M39×3 - - 29,2 36 24b - -
  • Surface integrity shall be in accordance with ISO 6157-2.
  • The Vickers hardness test is the reference method for acceptance (see 9.2.4).
  • a Minimum value for high nuts (style 2): 195 HV (185 HB).
  • b Maximum value for high nuts (style 2): 302 HV (287 HB; 30 HRC).
  • c Minimum value for high nuts (style 2): 250 HV (238 HB; 22,2 HRC)

Minimum Vickers hardness suggested for regular nuts (style 1) with D < M5

Thread D Minimum Vickers hardness of nuts HV
Property class
5 6 8 10 12
M3 151 178 233 284b 347
M3,5 157 184b 240 294b 357
M4b 147 174b 228 277 337

Dimensions

Property class 4b 5
Marking symbol 4b 5

ISO 898-2 Hex Nut Dimensions

Thread   D Width across flats s mm Minimum height of hexagon nut
Regular nut (style 1) High nut (style 2)
mmin mm mmin/D mmin mm mmin/D
M5 8 4,40 0,88 4,80 0,96
M6 10 4,90 0,82 5,40 0,90
M7 11 6,14b 0,88 6,84b 0,98
M8 13 6,44b 0,81 7,14b 0,90
M10 16 8,04b 0,80 8,94b 0,89
M12 18 10,37 0,86 11,57 0,96
M14b 21 12,10 0,86 13,40 0,96
M16 24b 14,10 0,88 15,70 0,98
M18 27 15,10 0,84b 16,90 0,94b
M20 30 16,90 0,85 19,00 0,95
M22 34b 18,10 0,82 20,50 0,93
M24b 36 20,20 0,84b 22,60 0,94b
M27 41 22,50 0,83 25,40 0,94b
M30 46 24,30 0,81 27,30 0,91
M33 50 27,40 0,83 30,90 0,94b
M36 55 29,40 0,82 33,10 0,92
M39 60 31,80 0,82 35,90 0,92

ISO 898-2 Bolting Surface Treatment Specifications