Instructions for Oil Hardening

Determining what type of steel is in any given piece of metal is not always easy, so knowing the appropriate method for hardening the steel isn't always known. If your steel is one that should be hardened in oil, yet you quench it in water, it could crack and warp. On the other hand, if you put hot steel in oil that should be quenched in water, nothing will happen. The steel will remain soft. Sometimes a metal expert can tell the type of steel by the sparks produced from grinding, but whatever the case, hardening oil is essential for many types of steel and knowing what types of oils harden steel, and which ones do not, is also important.

Difficulty:

Moderate

Instructions

Things You'll Need

• Forge furnace Metal tongs Gloves Pyrometer Magnet Peanut oil Deep fryer Sandblaster Grinder

1. Prepare a forge fire for heating steel. Metal is better heated in an oxygen-free atmosphere rather than with an open air torch. Wear gloves and use a pair of long metal tongs for holding your steel.

2. Heat the steel to the critical temperature of 1,450 degrees F. Measure the heat with a pyrometer. If you do not have a way to properly measure the temperature, try attracting the steel to a magnet. A piece of metal raised to such high temperatures is not attractive to a magnet.

3. Quench the hot steel in a vat of pre-heated peanut oil. The flash point of peanut oil is very high so there is less risk of the oil catching on fire. Do not use almond or olive oil as they do not harden steel.

4. Quickly dunk the steel in the 150-degree F oil and stir it around for 3 minutes to let it cool down. Remove the steel from the oil and let it air cool. The oil hardened steel should now be hard and brittle.

5. Temper the steel to a usable hardness by throwing it into a deep fryer vat of oil heated to 325 degrees F. Continue to heat and cool your steel until it is the hardness you desire. You can sandblast or grind the metal when finished.

Tips & Warnings

• Add a charcoal briquette to the forge fire to soak up any extra oxygen.

• When heating your steel, be careful not to heat it to point where it becomes white. This extreme heat will melt the steel.