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Jean Turner, RPT
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How to heat treat 01 steel.

Please note:
  1. It is assumed that the maker has basic skills involving use of a hot flame and the dangers involved with burning yourself with hot metal or oil... and what to do if you are stupid/unlucky enough to do so!
  2. Be sure to read, understand and follow all the safety instruction on the products you use.
  3. This is how I do it. You follow my method at your own risk.

One of the most asked questions is 'How do you heat treat your knives?'

Heat treating is not actually as difficult as it sounds. I remember how long it took me to have a try because of the apparent difficulty of the task. When I actually took the plunge - I was sorry I hadn't done so sooner. It is very easy if you use a logical process.

Once you do it you also realise you are carrying on a centuries-old tradition...

Working by colour comes with experience. For the beginning - use the magnet test. It's simple and it works.

Get yourself a reasonably good sized magnet. Mine is 50mm in diameter. I set this on one of my refractory bricks that I arrange as my 'furnace' - one air thermalite airbrick as sold by B&Q for 99p as my base. On that I position 2 refractory bricks (Bath pottery suppliers is where I got them - but more thermalight bricks cut down to size would work very well too and are cheap to replace when they start to crumble) to make an opening about the size of a can of beans. I stand a brick behind, standing on end and on the same surface as the thermalite brick, leaving a gap of around 15mm, and put one on top. This also leaves a little gap as the height of the back brick is slightly higher than the height of the 'walls'. It makes a 5-sided house into which you put your blades one at a time to start with - with the handles sticking out slightly. You will use pliers or as I do - a monkey wrench to grip the handle. Wear gloves and eye protection as sometimes the oil can spatter. Ensure your bean can is 100% dry before you pour your oil in - it can make a steam explosion, and here endeth the health and safety. Don't burn yourself. You are more important than a piece of steel and some bricks! If you drop your blade, leave it to go cold, normalise it and try again.

To the side of your favoured hand, have a bean can which is filled up with oil for quenching.

Heat your blade up using your bowtorch/plumbers wand until the knife glows a nice cherry red colour - every so often - aim the wand at the oil can to warm it slightly. Not too hot, and it's not essential when you first start. (ideally 75C)

When 01 is at martensitic temperature - it becomes non-magnetic. This makes it really easy to test if it is at the right temp for quenching. So - heat the blade up till it is cherry red, grip with your monkey wrench and take it out, touch it to the magnet (it helps here if your magnet is a circle and has a wire 'string' attached so you can pull it off the blade if it sticks). If it sticks - your metal isn't hot enough. Put it back in and take it higher. When it has reached what they term a 'bright cherry red', take it out and touch it to the magnet. If it does not stick - it is right - pop it into your can of oil and leave it to cool.

If you take the metal too high and you get sparks - then you are burning the metal. Don't take it into the yellow colour range.

Easy as pie.

Then you just temper it:

Clean the scale from the heat treat off the blade using some 240 abrasive lubricated with some Duck or WD40 oil - until it is silver.

In the meantime heat your domestic oven up till it is as hot as it will go (240C or thereabouts). Wrap the blade in ali foil, put on a baking tray and pop it in the oven. Count about 40 minutes and remove from the oven. If you have done it right - the blade should be a light gold or mid gold in colour. If it has gone dark gold or blue or grey or black you have gone too far - then you have to re-do the heat treat from the beginning, quench and then re-temper the blade (reduce your time by 5 mins at a time until you get it just right - keep notes).

Now what could be easier than that?

You clean off the tempering oxides (the gold) with your abrasive and duck/wd40 oil again and polish and sharpen your blade.

Just get in there and do it. If you get it wrong - just heat up, let cool, heat up, let cool - and then heat treat again.

Have fun - which is what it is all about

Hope this helps.

The funny thing about learning how to heat treat metal is is suddenly gives you the urge to heat metal to red hot and hit it with a hammer...