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Now that the edge has been hardened, the blade is almost ready to be sharpened, cleaned up and ready to go. But before we jump the gun we need to "temper" the blade a bit.

During the hardening process, although we attempted to only harden the edge of the blade, it's possible (likely) that we hardened the edge a little too far up the blade. Ideally only the bottom 1/3 of the blade will be hard, with the rest remaining flexible. This will allow the blade to bend without breaking if placed under extreme duress.

This process is a bit tricky and difficult to explain without witnessing first hand. It involves three cycles of heating with an oxy torch and successive cooling in a pan of water. Careful attention to the changing color of the metal is the key to success here. If somehow you manage to go to far, you'll ruin the previous effects of hardening and have to go back to normalizing and begin again.

Stage 1

Video and pictures coming soon

Stage 2

Video and pictures coming soon

Stage 3

For more information on tempering, here is an excerpt from The 1924 edition of Machinery's Handbook and there is a good article at Engineering Fundamentals.

Next Step

Beginning - Definitions - Forging - Normalizing - Grinding - Hardening - Tempering - Summary


This page last updated 12/30/2004
Copyright 1996-2005© John Pozadzides. All rights reserved.