How to heat treat O1 tool steel
Begin by wrapping the piece in stainless steel tool wrap and leave an extra two inches on each end of the package (This will be for handling purposes). The foil should be double crimped around the edges. Note: be careful to not tear or puncture the wrap!
Once wrapped place in the furnace and heat to 1450F. Upon reaching this temperature immediately begin timing the soak for 15 to 20 minutes. (Soak time is the amount of time the steel is held at the desired temperature; which is in this case 1450 degrees Fahrenheit)
Note: soak times will very depending on steel thickness. See formula at the bottom of page.
When the soak time is complete, very quickly but carefully take the package out with tongs, and hold over a quench tank then snip the end of the package to allow the piece to drop out into the oil. Be sure to have some kind of wire basket already placed in the quench tank to raise and lower the piece in the oil rather than have it lie still. This must be done to ensure a proper quench.
NOTE: For full hardness; it is critical that the piece enter the quenching oil as quickly as possible after taking them from the furnace!
If treating a knife carefully remove it from the tool wrap and quench holding it at a non crucial point such as the rear of the tang making sure to move the blade up and down in the oil as mentioned above for a proper quench.
Once the piece has been quenched down to around 125F begin the tempering process. To temper the piece it must be placed back into the furnace at 375F. Allow them to soak for 2 hours then remove the piece and allow it to cool to room temperature. The piece should now be approx hardness 60 RC.
Tip: Some have successfully used toaster ovens to complete the tempering cycle.
Tip: for added stability and a little extra hardness the blades can be placed in dry ice for one hour.
Tip: The oil should be warm and thin at the time of quenching it should also have a safe flash point. Some prefer to use olive oil rather than petroleum based quenching oils because of it's higher flash point. It is common practice to have one gallon of quenching oil for each pound of steel. To warm the oil before quenching simply heat a piece of scrap steel and drop it into the oil.
Note: Pre quench soak times can very to some degree. However, commonly one can figure about 1 hour of soak at hardening temperature per inch of steel thickness
1 inch = 1hour
1/2 inch = 30mins
1/4 inch = 15mins
1/8inch = 7.5mins