Case Hardening Wide copy

What does it mean to Case Harden a fastener?

May 17, 2022

Case Hardening, also known as Surface Hardening, is a heat treating process that makes the outer surface of steel stronger while leaving the inner core of the parts softer, as illustrated in figure 1. 

There are 5 different types of Case Hardening processes that you should be aware of: 

    •    Carburizing
    •    Nitriding
    •    Cyaniding
    •    Induction Hardening
    •    Flame Hardening

It is important to keep in mind that Earnest Machine will utilize the best case hardening process needed for the specific application, ensuring that your product provides the correct amount of wear resistance, longevity, and avoids embrittlement. 

What type of Case Hardened product does Earnest Machine offer?

Earnest Machine offers a complete line of Case Hardened Hex Serrated Flange Product, which includes Hex Serrated Flange Screws, Hex Serrated Flange Lock Nuts, and a line of Large Flange Hex Serrated Flange Lock Nuts. All of which are offered in a wide selection of diameters and lengths, ranging from the most popular sizes used within the industry to those hard-to-find sizes as well. 

Why Case Harden Hex Serrated Flange Product?

Hex Serrated Flange Product features serrated teeth under the bearing face of the flange, which works to create the locking action needed when fastening together steel-to-steel components. 

The Case Hardening process is important because it increases the surface hardness of the fastener to levels greater than Grade 8 product, resulting in increased surface strength, higher wear resistance, and stronger teeth that “bite” into the material they’re being tightened against.

Without the added bite that the Case Hardening process provides, the tips of the serrated teeth could roll over and become dull when tightened, comprising their locking ability. When fasteners with a locking action are used to fasten steel-on-steel components, you’ll want the added strength that Case Hardening provides, as the teeth will truly grip their installation surface and resist loosening better than standard Grade 5 product. 

For more information on Earnest Machine’s line of Case Hardened product, give us a call at +44 (0) 1902 711041 or email us at

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