TURN UP THE HEAT

When my wife and I were in Japan in 2006 we visited a traditional Japanese knife maker on the island of Kyushu. He is one of a handful of traditional knife makers left in Japan, with the family business stretching back for 250 years. The interesting thing was that he heated his forge using used engine oil. The burner was a very simple oil-atomizing arrangement using compressed air blown over a nozzle. The oil was directed into a brick furnace in which he heated his knife blanks. You can see a video of his furnace on The Shed website. The furnace ran with no apparent smoke or smell and achieved temperatures in excess of 1100°C. It inspired me to try to make my own.

There is always something fascinating about viewing the red-hot interior of a knife-making or blacksmith’s forge (Image 1).

In this article I will explain how I made a brick forge that runs on LPG, and a tank forge that runs on used engine oil or LPG.

“Forges should only be used where there is good ventilation”

Hazards

There are a number of hazards that you need to be aware of if you want to run any forge.

The high temperatures can cause serious burns and hot metal will easily cause a fire if it dropped on combustible surfaces. Forges should only be used where there is good ventilation. Carbon-monoxide levels can rise wherever there is combustion, so don’t use them in enclosed spaces.

Eye, body, and hearing protection is just common sense. A red-hot piece of slag from hammering hot steel could cause loss of sight if it gets into your eye. An old blacksmith that I spoke to recounted how he had several months off work due to a piece of slag