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 typeRangeZinc 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*
30028529,865,5|
31029531,065,8|
32030432,266,4|320 HV
33031433,367,0||
33531933,967,3335 HV|
34032534,467,6|
35033335,568,1|
36034236,668,7|
37035237,769,2|
38036138,869,8380 HV
38536639,370,1385 HV
39037139,870,3|
40038040,870,8|
41039041,871,4|
42039942,771,8|
43040943,672,3|
43541444,172,5435 HV
44041844,572,8
46043746,173,6
480(456)47,774,5
500(475)49,175,3
520(494)50,576,1
540(513)51,776,7

 

* 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.