Another +1 for 1080/1084. I'm a fairly new maker and the suggestions I got a year ago mirror what is being said here. I do stock removal with a basic forge for HT so I wanted a "simple" steel. I have yet to try Aldo's 1084 but it's going to be my next steel to try. My current stuff is from Kelly Cupples and I'm loving it. I got 1/8" cold rolled and it's great. The hot rolled 3/16 is good but not quite as quick and easy to work with due to the slight scaling from the hot roll.
My HT method for 1080, which would be the same for 1084, is as follows:
1. Normalize in a three step process, described here and many other places, basically each step reduces the temp slightly to keep grain size to a minimum. This is generally considered optional with stock removal but I do a lot of single sided grinds and have found it helps minimize the curl from the next two steps.
2. Bring up to and then just past critical. This is just slightly past non magnetic. The beauty of 1080/1084 is that you don't need to go higher and you don't need to hold it there any longer than needed to get the whole piece to harden up to that temp. Soak time is not needed beyond any required to even out the heat. I generally do this by eye now but if lighting conditions are odd or I just want to verify I will use a magnet during the initial normalization cycle which comes to this temp as a way to retrain my eye as to what critical looks like that particular day. Basically, critical then a shade or a shade and a half hotter is all you need for these steels.
3. Into the warmed quench. I use a tank body meant for compressed nitrogen, slightly larger than your standard SCUBA tank, filled 3/4 of the way up with canola oil. I preheat the oil to "hot but not burning" basically I warm it up via the back vent of the forge to the point where I can dunk my finger but it feels hot. Harder to describe than do, and again, the lack of precision is because of the steel's forgiveness, it's not that picky really.
My quench method depends on the knife, and unfortunately my tank is vertical with a limited cross section so doing an edge quench isn't possible, the closest I can come is to lower it in with a sweeping motion rather than just point first plunge. I very often do a straight in plunge with smaller and less pointy blades. Once in it gets fairly rapid agitation. I mostly do straight up and down, taking advantage of my tank style. This is equivalent to the stroke often discussed when using horizontal tanks that are fairly long but shallow where you basically run the blade from one end to the other as if spearing the quench. I also do a spine/edge motion, careful to not bang the sides of the tank. I am careful to NOT introduce any side to side motion though. After the initial quench (30 seconds or so, it's essentially done much faster but I'm also getting it cool enough to be safer when handling) I generally pull it out to check for any cracking or other major issues then back in long enough to be cooled to oil temp. That means the blade is down to around 120-150f. At that point I lift it out and let the oil drain off, wipe it down with a disposable shop style paper towel and either start the next one if doing several or immediately head inside for tempering. If doing multiples I limit how long I'll spend before starting tempering. if it's taking a bit I'll start the first ones tempering and then come back to the hot work. Usually I'm only doing two or three and I normalize them all first, so it's just "up to temp, quench" which can be pretty fast.
4. Tempering in my case is a high quality Kitchenaid toaster oven that has a tray AND a grate. The overall design means that unlike many toaster ovens it is a very even heat inside and doesn't fluctuate much once up to temp. I preheat it to 400 and run the knives for 1 hour temper cycles. I'll do the first run with them laying on one side, then after they're fully cooled I'll do another run with them laying the other way. Probably not important, but I see no reason not to. A while back I did some testing with my steel and tempering variations. I could tell a difference if I went much over or under on temp. I could also tell a difference if I only did one cycle rather than two. I tried one two hour cycle and it fell somewhere in between the two. Two two hour cycles didn't seem any better than two one hour cycles so I decided to keep my electric bill down. I could NOT tell any difference between two and three cycles. I know some folks suggest longer cycles, or three cycles... and with other steels that's certainly important. With the 1080 I'm using my two one hour cycles seems to do the job right so that's what I'm doing.
Obviously if you want harder or softer you can adjust the temp, but at least according to the charts there's not much functional room to mess with, you quickly become brittle or mushy. My couple attempts at increasing hardness have survived but the edge doesn't hold up well. In order to limit chipping and micro fracturing I have to make it a more obtuse angle which defeats the purpose in most cases. I haven't had any BREAK under reasonable testing, in fact one little needle tip guy has seen a fair bit of use and hasn't snapped the point yet, but the edge performance just isn't as good. Likewise, softer is not much use. One of the beauties of 1080/1084 is just how darn tough it is, so reducing hardness to increase toughness is not that worthwhile a trade off in a knife. My test knives all work fine and take a decent edge, and then lose that edge really fast. It rolls generally, or just kinda mushrooms slightly, hard to describe. It's not damaged, it's just not sharp anymore. The 400 I've settled on as my best middle ground is MY thermometer's number, you'll have to test for your own, with your own tempering oven and steel. I have no idea if it really is 400 or not, but once up to temp it stays at an indicated 400 +-10 for the whole time. That gives me a very tough blade, tough edge that holds up decently AND gets very sharp. I've been very impressed with just how much abuse my knives can take when done this way. It's not an everlasting edge, but it resharpens easily and doesn't ding up on contact with hard materials or get dull just because you sliced some hemp rope or a piece of high test fishing line. The popular ABS test of chopping through a 2x4 does pretty well, though my sharpening skills aren't really as good as they could be. I also don't make knives suited for chopping, but I've done it as a test of the edge/heat treat and been pleased.
ALL credit for what I do correctly goes to the folks here who have offered advice and technical information. Anything I've got wrong is just my stupidity. I'm the first to admit that my methods are not optimal, but that's why I haven't moved to a more picky steel. My less than precise controls, technique and equipment are counter balanced by the extreme latitude of the steel. My methods work for ME with my materials and conditions, for anyone else I can only say they're a reasonable place to start from to find your own methods.
1084, 15n20 and 52100. Going to start forging soon. If you are already forging, you must have an oven or forge and could HT O1 by yourself with a little trial and error on some scrap. It won't be the perfect treatment but you will get satisfactory results until you can invest in HT specific equipment.