I'm going to jump i here and make a comment or two.
The quench, for the sake of this discussion, is a deliberate plunge into the oil, not a slow movement. Not a splash or a slosh, just stick it in there. A slow action would allow the blade or parts of it to cool below the necessary temperature to acheive the transition to full hardness.
Also the only "swirling" action should be a "slicing" or "sawing" of the oil, IF ANY. Please dont "paddle" it as with a boat paddle. You'll warp your blade a higher percentage of the time paddling. When you paddle from side to side the quench is sucking the heat out of the steel at an un even rate. Warpage. If you dont allow for the even reduction of heat, there cant help but be more stress pulling at one side or another. Thus warpage.
I mentioned EVEN HEATING. If you want to be successful at heat treating, you have to think EVEN HEATING AND EVEN COOLING. For that to happen you must have a CONTROLLABLE HEAT SOURCE. That means large enough and steady/contollable enough. You must have the right QUENCHANT. That means an oil of some sort most of the time. You also must have the right METHODS to get it done in the right sequence.
Some post I've read here mention off the wall, risky methods of heating and quenching (I am speaking mostly of comments about mis-information, not solid alternative methods). Sometime you will get lucky doing that, but more often than not the blade shaped piece of steel just survived the process in one piece but the guts of the knife are pretty tore up. In other words, a high percentage of them are not hardened all the way along the edge or are left too hard or too soft after the draw. OR worse, the all important grain has grown to the size of sand grains and the blade will break on you when you need it most. Most of the time the tip will break off in this circumstance leaving you scratching your head. I'll tell you why. Because of un even heating and cooling and poor methods.
BTW, you'll see lots of things on ***tube that are not things you want to do. I watch it too, but I skip over some of the stuff that I know will get me in trouble.
A file is mystery steel. We think it's 1095 or W2 or whatever. If you are going to use mystery steel, there is a logical approach to the heat treat. You can not take an arbitrary recipe from the internet or from an old timer and hope to get a good knife out of it if you dont know the type of steel.*edited to clarify: unless you know how to properly test.* Assuming it is 1095, then you have to do your part with the heat source, quenchant, and methods.
You might review this thread from a while back.
My Thoughts on Heat Treating