Glad to hear I was able to help straighten that out a bit for ya.
(edit: I just realized you asked if a small propane "torch" should get hot enough. I read that to be a small propane "forge", which is the reason for the answer I give below. But no, a propane torch alone won't get it hot enough, although it should if there is a forge built around it
) You can check out the very first video posted on my Youtube channel that shows my first forge made from a paint can using "kaowool" and refractory cement. There is a link to my channel at the end of each of my comments under my name.)
As far as a small propane forge getting hot enough I would say most likely yes, it should. Of course it depends on how well it's insulated and how well the burner works that you're using for it. Even a properly made soup can forge should get over 1500F, but it's definitely not ideal for getting and maintaining an even heat. The main things you want to keep an eye out for while heating the file up would be to not overheat it, and getting an even heat along the entire file. Some guys will anneal the blade end first and the the tang second (or vise versa), as it's easier to keep a more even heat along a shorter length. It really helps to keep moving the entire piece slowly in and out of the forge and under the direct flame in the forge. Make sure to keep checking with a magnet (a small telescoping pickup magnet works well as you can test the steel while it's still in the forge, but any will do), which will tell you when you've reached about 1414F, which is when the iron in the steel becomes non-magnetic. Once you reach non-magnetic, just heat it a bit more (but not too much!) to reach the ~1500 critical temp.
You want to try your best to at least avoid reaching 1600F and above as that will cause the grain to grow to a large size, which can/will cause the knife to be more brittle and cause the edge to chip easier, even at a lesser overall hardness than a blade with nice fine (almost 'silky' looking) graincstructure. This is where thermal cycling the steel comes in (such as after forging a blade), which allows you to reduce the size of the grain with successively descending heats. Thermal cycling usually goes something like this: heat to 1600F air cool to black, heat to 1550 air cool to black, heat to 1500 air cool to black heat to 1450 air cool to black. The grain condition of quality steel files is already excellent and is why if you are just doing stock removal, it can be better to just temper it back and grind/shape while keeping it cool with water. But you need practice and the proper tools to do that.
You can get a good look at the size and texture of the grain by clamping about the file about an inch from the top in a vise and breaking that end off with a hammer. You can also heat up the end of a scrap file in your forge to as hot as you can, quench it in water and then do the same thing again. This will show you firstly what you DO want the grain to look like, and secondly what you DON'T want the grain to look like. Here is a Youtube video by Lewis Razors that gives you an idea of what that all looks like:
I do apologize for these long comments as well as for getting a bit technical, but sometimes it's hard to explain one step without explaining 'why', or explaining another. I would suggest first practicing on some scraps of mild steel that are similar in size to your file (along with a magnet) to give you an idea of how hot non-magnetic is as well as give you some practice keeping an even heat along the entire piece.
I don't mean this in a rude way, but it is very likely you will make some mistakes a first, but that is how we all learn! As long as you don't set unrealistic standards for you first few knives and make sure to finish each one you begin you will be good. Learning how to fix/correct your mistakes is probably the most valuable skill one can learn in knife making.
Let me know how it goes. If you have any other questions I will try my best to answer them. Take care
~Paul
My YT Channel Lsubslimed
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(It's been a few years since my last upload)
