As with all posts on this site, I’ve got to remind you that your safety is your responsibility and if you choose to copy anything you see here, that’s your responsibility. Also I’m not rich so if you hurt yourself and sue me, you won’t get a big payout.
Recently I wanted to make a special hook-shaped chisel to cut the inside of wooden bowls on a lathe. I had some good quality steel rod lying around, and I discovered just how easy it is to make a fire hot enough to make steel soft or even melt it entirely. We’re talking about the region from about 900-1200 centigrade. I suspect the art of smithing is to get the temperature and quenching (rapidly cooling the piece you’re working on in water) just right to achieve the hardness you need – but I don’t know much about that yet. It’s just fun to experiment with, if you take common sense safety precautions.
To stay safe you’d certainly need a full face guard, leather gauntlets and a leather apron. Don’t take that as any guarantee of safety! As I wrote above, your safety is your responsibility.
To assemble the forge, first I drilled roughly 16 x 10mm holes in the base of a thick steel turkey tin, in a rough grid. I built a base out of bricks to hold it off the paving stones because it could get hot enough to crack them. I left a 15mm gap between two of the bricks to one side (important!). Just to be sure the tin wouldn’t get knocked off or blow away (it’s quite light) I placed a brick inside it too, leaving all the holes in the bottom uncovered.
Before I lit it, I made sure I had a large metal container of water handy – not just for safety, but to quench the hot steel once I’d shaped it.
I filled the tin with charcoal and lit it using kitchen towel and a blowlamp. I know that’s not the ‘authentic’ way to light a BBQ, but I’m an impatient person. So, I had a barbeque. To make a barbeque into a forge, you need to force – feed it with air to up the temperature. That’s where the bellows in old-fashioned smithys came in. Modern forges sometimes use gas. To get my forced air, I used a vacuum cleaner with a blow function. I pushed a 15mm diameter steel tube into the end of the vacuum cleaner hose and sealed the gaps in the joint with duct tape. That keeps the plastic hose away from the 1000 degree heat. And again, this is a BLOWING vacuum cleaner. If you accidentally use one that sucks, it won’t last long once it’s sucking up burning bits of charcoal.
Once I had all my safety gear on, I turned on the vacuum cleaner and slowly introduced the steel tube into the gap between the bricks, pointing it upwards towards the holes in the bottom of the turkey tin, forcing air through the charcoal. I had to experiment with the angle of the tube, because if the airflow is too powerful, it can lift the burning charcoal straight out of the tin. The charcoal began to glow and emit glowing burning gases, and I pushed the rod into the centre of the glow.
I had to heat the end of the rod several times in the fire while I was shaping it – I found it needed to be glowing red to be soft enough. I used the head of a sledgehammer as an anvil, and a normal ball pein hammer to hit the rod.
THE OTHER FORGE
I managed to reach even higher temperatures with this one. It’s based on a very large nitrogen bottle with a hatch cut into one side. I think the temperature was greater because 1/3 of the steel tube passed through the fire, so by the time the air left the tube it was already very hot. In my first design, the air was cold when it hit the fire.