Washer hardness

In order to assure the unique wedge locking function of the Nord-Lock washers, the hardness of the mating surfaces should not exceed the hardness of the Nord-Lock washers.

Nord-Lock washer hardness table

Washer type Range Zinc flake coated
flZnnc – 600
Non coated
Steel washers
(Through hardened)
NL3 – NL42
NL45 – NL130
≥ 465 HV1
≥ 465 HV1
Stainless steel washers
(Surface hardened)
NL3 ss – NL80 ss ≥ 520 HV0,05
SMO 254® washers ≥ 600 HV0,05

 

Hardness conversion table

Vickers
HV
Brinell
HB
Rockwell
HRC
Rockwell
HRA
8.8
bolt*
10.9 bolt* 12.9
bolt*
300 285 29,8 65,5 |
310 295 31,0 65,8 |
320 304 32,2 66,4 | 320 HV
330 314 33,3 67,0 | |
335 319 33,9 67,3 335 HV |
340 325 34,4 67,6 |
350 333 35,5 68,1 |
360 342 36,6 68,7 |
370 352 37,7 69,2 |
380 361 38,8 69,8 380 HV
385 366 39,3 70,1 385 HV
390 371 39,8 70,3 |
400 380 40,8 70,8 |
410 390 41,8 71,4 |
420 399 42,7 71,8 |
430 409 43,6 72,3 |
435 414 44,1 72,5 435 HV
440 418 44,5 72,8
460 437 46,1 73,6
480 (456) 47,7 74,5
500 (475) 49,1 75,3
520 (494) 50,5 76,1
540 (513) 51,7 76,7

 

* In order to assure the unique mechanical locking function of the Nord-Lock washers, the hardness of the mating surfaces must be lower than the hardness of the Nord-Lock washers.

The table shows the range of minimum and maximum hardness values according to ISO 898-1 for the stated standard bolt grades.