Originally Posted by
kyratshooter
You are not going to get an "exact" level of hardness using a home oven. Too many variables and exact hardness is not critical within the range you have specified for the job you are doing.
If it is a simple ferro rod scraper it will probably work right now!
What will be more critical will be the edge of the bevel and how it is presented to the ferro rod.
As long as it has a good sharp corner it will work, just like a piece of broken glass, the spine of a cheap knife, the spine of a good knife, a hunk of broken hacksaw blade, or a flake of chert will work.
Even if you were making a knife there would be more factors than hardness to consider, like ease of sharpening, brittleness, edge holding ability, grind pattern, size and use of the blade, and the most important, personal preference.