I've been researching the steel I used for this knife and a couple I just recently finished. As I said, I contacted the manufacturer (Oldham Saw Company, which is now owned by Black and Decker). They gave me the above specs for the blade, which was NOT carbide tipped. I also found an online resource that tested several scrap steels for their alloy content, including this blade. Here is a quote from that site:
"A very clean straight high carbon steel. If they do call it "1069" (which is an SAE-only listing) it's an extra clean and sound 1069. It's not a ".70%C W1" tho, too much Mn (.10% to .40%Mn for W1)."
Does this analysis sound correct? At any rate, I assumed it was and treated it as a 10-series steel. Here's what I did on the last three 4" blades I made, all with the same results (remember that the blade is small and is 3/32" thick):
1) After cutting it out and grinding it to shape, I did a three stage thermal cycling as Karl describes, only not as hot on the first stage (he calls for temps as hot as the original forging temps, which I obviously don't know). To be safe, on the first stage I allowed the steel to reach non-magnetic, checking it every 30 seconds or so for color (I was working outside at night in the dark) and for magnetism with a magnet. When it reached non-magnetic, I let it soak for 1 more minute. I let it cool to black, then heated it again until it hit non-magnetic (checking as before). I quickly removed it, let it cool to black, and then heated it back up to just below non-magnetic. This time I let it cool completely.
2) I heated it to non-magnetic (checking it as before), and then quenched it in 1 gallon of peanut oil heated to 140 degrees F (verified with a digital thermometer). I plunged the blade in point first up to the first tang hole. After about a minute I plunged the tang in and allowed it to sit submerged for about 3 minutes. I then pulled it out and cooled it in water.
3) To temper it, I gave it two 1-hour cycles in the oven set at 400 degrees F (verified by a second over thermometer). I preheated the oven for 20 minutes before putting the blade in.
4) I ground a convex primary and flat secondary edge. The edge neither rolled nor chipped on a brass rod and still shaved hair after about five minutes of whittling and hacking on a piece of osage.
Any thoughts? Thanks for the help, fellas!