HT is as much an art as it is a science when using simple methods. Here are a few things that can get better results:
Use a magnet to determine when the steel reaches 1414F. It will suddenly stop attracting the blade at that temperature. The temp you want for most simple carbon steels is about 50-75F higher than that. That will be about one shade of red brighter.
Do your HT in a reasonably dim location. You can see the colors much better that way. I prefer to do HT by color at night and with only a single 75W light burning behind me. Avoid bright sunlight, as it greatly changes the colors you see. At the very least, do the HT in full shade.
Heat as evenly as possible. Keep the blade moving and turning. Try and heat the spine first, and allow the color to move toward the edge and tip. It is often hard to avoid, but try and not overheat the edge and tip any more than you can. Also, remember that it is the edge that you need hard. If the entire edge is at the right temperature, go ahead and quench.
Don't be afraid to re-do a HT. If after the quench the edge is still soft, just do it over and heat a little more. Test the edge right after quench with a newer file. File the edge at a 45° angle and see if it skates like you were filing on glass. If the edge is hard, good. If it files away easily, try again. Sometimes it takes a couple of file strokes to cut away the decarb and hit the hard steel, so if it bites in, give it a few more strokes before declaring it a bad HT.
A good setup for a torch HT is to place the bricks to make an "L" or a sideways "U". Hold the blade in the sheltered place and use the torch with the other hand to heat it up by playing the flame over it. Long nose pliers from HF work fine for HT tongs. Go slow and watch the blade as it heats up. Have the magnet stuck on something next to the heating area, and occasionally touch the blade to it as it gets red. When it stops sticking to the magnet, the steel is at 1414F. Heat a little higher and quench immediately in warm ( 120-130F) canola oil.
Before you do HT on a blade you have a lot of time in, practice on some steel. Get a bar of the same type steel you will be using to make your knife from. About 1/8" by 3/4" works well. Cut half a dozen 4" pieces off and very roughly grind an edge on them with a point on one end. No need to make it pretty or knife looking, just an edge and a tip is all you need. Practice doing your HT on these ( you can re-use these several times) and learn how the steel looks and how to use your torch and magnet to get the steel to right at 1475-1500F. Once you have that down pat, do the actual knife.
For the type of HT methods you will be doing, use the most simple to HT steels. 1084 is called the eutectoid, and is the easiest. 1060, 1070, 1075, 1080 will also work with simple HT methods. 5160 and O-1 aren't too bad, but you have to try and hold them for a minute or two at the target temp. Don't try higher alloy or hyper-eutectoid steels. 1095, 52100, W2, and any air hardening or stainless steel will need a better HT method.
