Here is my design for a budget forge - if you are heat treating your own irons then this little baby will be very useful. It costs next to nothing to make and works very, very well.
You will need-
The table leg has a flange welded to the top of the tube. I drilled matching holes in the wok to bolt it on.
Drill five holes through the flange to allow the air through and make matching holes in the wok.
With the wok bolted to the tube you will need to make some form of holder to safely hold the forge and the hairdryer.
Here is my simple solution from scrap around the workshop.
Cut the bottom out of the tin can and slice open one side to act as a holder for your work.
The can holds the charcoal together over the air entry holes.
Fill the can with charcoal and get the party started. Once the charcoal is burning nicely you can turn on the hairdryer.
Adjust how close the dryer is to the end of the tube to get enough (or just enough) air flow.
Plunge your iron into the forge and give it a couple of minutes - it will soon be at temperature. I have a tin of oil at hand to quench the iron when it reaches the correct heat and a small magnet to test it.
Needless to say, you will need tongs to handle the hot iron and safety clothing will be needed - it gets REAL hot! A fire extinguisher nearby is also a good idea. Safety lecture is now over.
Here's the iron you saw in the pictures (after tempering and sharpening!!). The forge easily lets you treat your own irons - this iron is 6mm thick.
Hope you find this useful - let me know if you make any worthwhile mods.
Philly