8.8 is not necessarily 8.8
8.8 is not necessarily 8.8
In the last few years and especially recently we have been asked by our customers again and again, why there are so considerable price differences concerning 8.8 and 10.9 thread rods and studs.
The explanation is quite simple:
There is a norm for nuts and screws, EN 898. It contains among other things, the definition of the strength classes and their mechanical properties.
Furthermore, this norm EN 898 defines exactly in Part 1 table 2, which chemical configuration the material of the screws must have. Screws of the strength class 8.8, 9.8, 10.9 as well as 12.9 must also be hardened and tempered. This means, the screws must have a tempered structure.
However, there are suppliers who raise the tensile strength by cold drawing of untempered steel and then offer and sell it accordingly as 8.8 or higher.
They knowingly sell a wrong and faulty product to the customer. Leaving the expensive heat treatment out, the prices of these screws are, as a matter of course, more favourable than those that are produced according to the norm.
We can only warn our customers against these practices, as, except for the tensile strength, neither the mechanical values, defined in EN898, are maintained, nor the physical properties (tempered structure). The customer’s claim is inevitable.
At Graewe, you only receive threaded rods and studs (beginning from strength class 8.8) that are produced out of tempered material. These rods are more expensive, but they conform to the norm and provide the customer with the certainty having bought a quality product.
