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"Cherry Red" for case hardening ?

I am a hobbyist experimenting in setting up a home shop. I was years ago familiar with a product called cherry red, that we used to borrow from a friends dad to harden home-made hunting knives. What is this and how/where can it be purchased. I am also trying to find out what is involved in "case-hardening"

I thank anyone in advance for your time.

W. Smith
SLC, Utah

Case Hardened steels

Case hardening is a process that has been developed over many years. Its value depends on the operating conditions of the gear to which it is applied. It is a technique to increase surface hardness and fatigue life for a component. In the process of case hardening, a steel alloy is heated up in an atmosphere of carbon or nitrogen. Diffusion of these atoms makes the outer surface harder than the inner core of the material. The surface layer or 'case' is normally on the order of 1 mm deep and makes the surface a lot harder and more wear resistant. The increased hardness within the 'case' also results in improved fatigue resistance for the component. The disadvantage is that the fracture toughness is worsened. This technique is much less expensive than hardening the entire gear wheel and it gives the gearwheel a hard shell or a 'case'. It can also be applied to gears, which are too large for heat-treatment furnaces. These gear wheels are mostly used in cars and aircraft where the weight is of great importance, this because they can be made smaller to take a larger load.

Simon Hulterstam
- Edinburgh, Scotland

Cherry red can be purchased from

Cathy Johnstone
- Cheshire, Connecticut

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