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Edit: I solved the issue by tempering twice more at 400.

I made my first blade out of 1084 today and I'm having some trouble tempering it. This is not my first knife, It's probably my 20th or higher and I have not had this issue before. I'll explain what I did so that you have a good understanding.

I use minimal equipment and do not have a digital oven. After the blade was forged I heated the blade in an LP forge, to an orange color and placed it in a container of vermiculite for several hours until it was cool. The blade was then rough ground.

Once the blade was ready for heat treat, I heated the blade to an orange color and let it sit at that temperature for approximately ten minutes. The, I let it cool to room temperature. I then reheated the knife to an orange red color, soaked again for approximately ten minutes, and let it cool to room temperature once more. Again the blade was heated, this time until it was red in color. It was held at this color/temperature for another ten minutes and then was cooled to room temperature.

Now, I was ready to harden the blade. I brought the knife blade to an orange/red color. I was aiming for a bright red color, but it went a little hotter by mistake. I held the blade at that color for around 3 minutes then quenched in McMaster-Carr 11 second quench oil. I let the blade cool to room temperature and placed it in the oven (toaster) for one hour at 300. I let the blade cool again to room temperature. A file would still glide over the edge. I tempered for another hour at 350. Same results. So, I tempered again at 400 for an hour. A file still glides over the edge, but cuts just a little. The spine is soft.

Is it possible that there is a carbide buildup on the surface? Should I grind with a heavy belt and see what the steel is like below the surface? I was not sure if I should continue to raise the temperature on the oven and re-temper until I have the desired results?

Any help would be great and I thank you in advance.

-Matthew M Paul