Case Hardening Do-It-Yourself: Quick Guide

If you make steel tools like I do, sometimes a hard surface is in order. There is a way to case-harden steel that is inexpensive and quick and can be done with an acetylene torch as the heat source. It uses a powder called Cherry Red that is available from tool supply houses.

Use this method when you need a local repair or prototype touch-up. If the part requires greater depth or strict metallurgical consistency, outsource hardening to a qualified heat-treat facility.

I use a heat-treating company to do the work if the part requires a certain depth of the case and hardness. For example, I get parts that require a case 0.003″ to 0.005″ thick and 62 HRC. I would not try to do that with the Cherry Red process, but if I make a tool or die for in-house use and want a case with an HRC above 55, then I’ll use it.

The heat treater that I use has a lot charge of $150. If I want a case on the end of a punch that is 0.75″ dia., I can do that with my acetylene torch for about $5 of material and 10 minutes of time. I like those numbers.

You don’t need much to get started. Image courtesy of B. Taylor

The process is simple.

1. Heat the area to be heat-treated to a cherry red color.

2. Coat the red area with the heat-treating compound. When I do the end of a punch, I put some compound in a tin can and plunge the tool in. Use a well-ventilated area or, better yet, do it outdoors because it gives off ammonia fumes when the compound is heated. Cherry Red comes in a plastic container, so don’t put hot metal in the container. And take care because the compound can irritate skin.