Question about theoretical vs. practical HT quality

[Curse The Sky]

Let's say a smith is making blades using a low-tech coal / charcoal forge for austenitizing (including a short soak where necessary), and relying on color, magnetism, and experience to get the right temperature. Further, they're quenching in pre-heated canola oil where appropriate, and tempering using their home oven.

If their blades are coming out with high and even/consistent hardness, very fine grain size, and no warp, how much else are they potentially "leaving on the table?" In other words, given relatively basic equipment but plenty of experience, how much performance would you expect to lose out on as opposed to a home HT oven, commercial quenchant, thermocouple to check temps, and other modern equipment? What about compared to sending off for a professional HT?

For sake of argument, let's assume we're only dealing with plain carbon steels and low alloy tool steels.

 

[Jason Volkert]

With low alloy steel and said person isn't over heating the steel and lets say its 1084 steel I doubt you are leaving anything on the table. But for low alloy steels like 52100 I think you would be leaving some stuff on table with a forge heat treat. Unless you had a real good forge like a drum forge that held real good temp with a pid.
Some low alloy steels like say 5160 if your 50degrees off your leaving like half the toughness or more on the table according to Larrins research on Knifesteelnerds.com.
I used to always heat treat with my forge and I got hard blades every single time. But after subscribing to knife steel nerds and reading info that I believe is solid info that I can trust. I went and bought a oven and a hardness tester. Heat treating now is soooooooo less stressful.