As a very amateur wood turner, I find good tools very pricey. Tried making a scraper out of an old file. Came out OK.

Made a paint can forge, using a MAP gas torch. Heated the file till non magnetic, quenched in chainsaw bar oil. [all i had on hand]. Then to the oven for 2 hours at 400. Its sharp, and cuts great, but a metal file scratches the surface, which I believe is a FAIL. Probably wont stay sharp for long. What can I do better to get it hard with basic tools and knowledge?

I also have a piece of M2 precision ground flat bar that I would like to grind into a scraper. Is it possible to "blue" this steel, like cheap carbon steel cutters, or can I just grind away?

On the file; it was already too hard to start; you could just draw temper on it to a good point and then take care grinding it to not let it get too hot and so avoid the whole quench harden step.

On the M2: you didn't say what the hardness to start with is---"precision ground flat bar"  can be hard, soft, intermediate...!

If it is hardened already to a proper degree for what you want you should be able to grind it and not mess up the temper. When I worked with the swordmaker we did all our grinding with the metal in our hands so that when it started to warm up we would know it before it went past the tempering temp.

Finally warmed, say 140 degF, vegetable oil will do a better job of hardening than the chainsaw oil.  Most kitchens have a bottle of oil in them.

Of course all of that is assuming the file was hardenable in the first place and not just case hardened

The M2 is just a blank off Amazon. No idea as to specs. Searching the web for tool steel suppliers, all seem to want to sell 3ft plus, no small quantities. The 3mm thickness may be an issue but cant find small thicker pieces anywhere.

uxcell HSS Tool Bit Square Lathe Turning Grinder Cutter Mill Blank 3mmx30mmx300mm

 

Good Point Steve; most of my "tool conversion files" are 50+ years old and not tend to have the "modern" file foibles and so I didn't think of that possibility.

Sync, the spark test should show if the metal left after grinding the surface is high C.

My last wood lathe tool job was for a high end vase turner who wanted some specialized curved shaft tools to hold metal lathe carbide inserts.  I told him to stop by the smithy. Pulled some stock I had to hand and stuck it in the forge. When the working end was hot I pulled it out, stuck it in the post vise and told him to bend it to the curve he wanted. First one went too far; so I told him to just push it back a bit.  We did a couple like that and next weekend I sold him an anvil, knowing the Emperor would be pleased that we had lured another one over to the dark side...

Since 20 to 22 foot is standard size for bars, 3ft IS a small quantity