How to Heat Treat Old Chisels

Heat treating an old chisel will harden the metal. When the metal is hardened, the chisel becomes stronger and more durable. The process involves heating the chisel to its critical temperature and cooling it with water. Heat treat a chisel when you want to reshape the blade to sharpen it. Heat treating a chisel requires the use of a blast furnace, so exercise caution and wear industry-regulated, molten-metal-resistant gear.

Blast furnace
Magnet
Bucket filled with water
Steel gripping tongs
Sanding block

Instructions

- 1
  Grip the handle of the chisel with steel gripping tongs. Insert the chisel into the fire of a blast furnace.
- 2
  Heat the chisel until a magnet no longer sticks to it. This indicates the chisel has reached its critical temperature.
- 3
  Remove the chisel from the heat and slowly dip it into water. Insert the blade end first and keep it submerged in the water until the handle turns dark red.
- 4
  Remove the chisel from the water and sand the blade with a sanding block. Continue sanding until the blade turns bronze.
- 5
  Submerge the chisel under water until it is completely cool.

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