Heat treating O1 Toolsteel in charcoal

[cloudradio]

I am very new to knife making and just finished my first ever knife made from steel scraps I had laying around.

I heat treated the blade in a charcoal fire with a hairdryer to get the temperature up and quenched it in canola oil.

For my next knife I ordered some O1 Tool Steel. I plan on doing the HT in the same way. However, I am not sure I got the last blade hot enough before the quench. Because I tested it on a scrap piece of the same metal, and it was definitely harder than before, but you could still bend it in a vice (i expected it to break instead). This test was done before temperering.

So, my question is:
How do you tell the correct temperature of your steel (without buying a thermometer) and for how long should the steel stay at that temp before going straight into the quench?
Is Canola oil good for quenching or should i be using a different oil?

thanks for sharing your knowledge


-Claudio

 

[Stacy E. Apelt - Bladesmith]

Get a cheap welding magnet from Harbor Freight. Stick it somewhere on the side of or next to your forge setup (not in a too hot place).

Heat the blade as evenly as possible, moving it around and turning it over all the time.

When it gets red, start checking it on the magnet. It will stop sticking to the magnet around 1425°F/775°C.

Heat just a little brighter red color (around 1475-1500°F (800-815°C) and quench. Canola is fine for O-1.

Let cool to room temperature while hanging in the air. One easy way to do that is to stick the tang on the magnet.

Temper twice at 400°F/205°C for one hour each cycle. To cool between tempers, just stick it in water or run the tap or a hose on the blade.

 

[cloudradio]

Thanks for the tips!
I will buy a welding magnet for temperature checking.

 

[DevinT]

If you are new to heat treating in a forge, too hot is usually the problem more than not hot enough.

Hoss

 

[Stacy E. Apelt - Bladesmith]

Additional Tip:
When you pull the blade out of the oil quench after 10 seconds, you can straighten any warps easily for about the next 20 seconds. Use gloves and bend it by hand or use a wooden mallet and pound it straight on a wooden board. Don't use the anvil or a metal hammer, as these will cool the blade faster. When you will feel the blade stiffening up, stop any attempt to straighten more.

The science behind this is when the blade passes 1000°F/540°C it remains austenite, which is very soft and bendable. It will start to convert to martensite at 400°F/200°C. That is when it stiffens and becomes very brittle. Any bend or shock once the blade starts this conversion will break the blade. Additional attempts to straighten have to be done at 400°F/200°C after the second temper cycle. The blade can be re-heated to that temperature and straightened as many times as is needed to work out a warp or twist.

 

[TheEdge01]

I am very new to knife making and just finished my first ever knife made from steel scraps I had laying around.

I heat treated the blade in a charcoal fire with a hairdryer to get the temperature up and quenched it in canola oil.

For my next knife I ordered some O1 Tool Steel. I plan on doing the HT in the same way. However, I am not sure I got the last blade hot enough before the quench. Because I tested it on a scrap piece of the same metal, and it was definitely harder than before, but you could still bend it in a vice (i expected it to break instead). This test was done before temperering.

So, my question is:
How do you tell the correct temperature of your steel (without buying a thermometer) and for how long should the steel stay at that temp before going straight into the quench?
Is Canola oil good for quenching or should i be using a different oil?

thanks for sharing your knowledge


-Claudio

The recommended soak time is 10min, but I don’t recommend attempting a soak using a forge. To avoid overheating and risking grain growth, you are better off getting your blade up to critical temp then quenching.

 

[Pinoy Knife]

here is a cool trick for ya
use table salt to check your temperature. it melts between 1450/1500 degrees
when you think you are hot enough sprinkle salt on the blade and see if it melts.

 

[Forest Ninja]

.

 

[Alex Topfer]

The recommended soak time is 10min, but I don’t recommend attempting a soak using a forge. To avoid overheating and risking grain growth, you are better off getting your blade up to critical temp then quenching.

With a charcoal forge could you get it to non-magnetic and then turn the air off to do a soak?
Not something I would try the first time but maybe a more advanced technique

 

[TheEdge01]

With a charcoal forge could you get it to non-magnetic and then turn the air off to do a soak?
Not something I would try the first time but maybe a more advanced technique

I don’t recommend it without a thermocouple. The blade would most certainly begin cooling as soon as the air was turned off, so more than likely it wouldn’t be a true soak to get the necessary carbon into solution. I still use my forge for larger blades that are too big for my oven, and I quench as soon as the blade is an even bright red color.