Rockwell testing is one, and probably the best-known, way of determining how hard the metal is.
The one encountered most frequently in this industry is the C scale, and ratings can run from C20 to C70-the higher the number, the harder the metal. For soft steels of medium or low carbon, the B scale is used. For extremely hard metals such as tungsten carbide, the A scale is used. Most hardware and tool ratings will range from the mid or high C30s (semihard) up to the C60s (very hard).
Check your state and local codes before starting any project. Follow all safety precautions. Information in this document has been furnished by the North American Retail Hardware Association (NRHA) and associated contributors. Every effort has been made to ensure accuracy and safety. Neither NRHA, any contributor nor the retailer can be held responsible for damages or injuries resulting from the use of the information in this document.