Interesting. I've called Peters awhile back. They're very expensive unless you send in a very large quanity of blades.
"Very Expensive" is a relative term.
If the sword comes out straight, hard, and not cracked, the price isn't expensive. If all your knives are perfectly HTed to exactly Rc60, and need very little post HT clean up, it isn't expensive. If the sword doesn't break in half on the first couple cuts, it isn't expensive.
When you finish the pre-HT work on a knife, set it in a box and start on another. When you have ten, send them to peters. You can get a couple hundred knives HTed for the price of a HT oven. Perfectly HTed knife blades ( especially stainless) for $5 or less each isn't expensive.
If I needed a Flu Shot, I would go to the cheapest doctor I could find. If I needed surgery, I would go to the best doctor I could find. That would be Peter's HT.
Paul Bos also does swords, IIRC.
All that said, a 36" sword is fun, but not really practical. Two 18" wakizashi or three 12" tanto would be much more doable and would likely come out better. In terms of salability, the multiple shorter swords or knives will be easier to sell, .... bring more money, ... than a longer single sword.
Now, for those who want to do a katana or wakizashi in carbon steel at home:
Using a forge with good temperature control and front and rear ports, one can HT any length blade.
Set up a long enough or deep enough quench tank with plenty of oil volume. Three to five gallons ( or more) is needed for a sword. The tank should be sturdily mounted or braced. A large oxygen/helium/nitrogen tank with the top cut off makes a great sword quench tank.
Get the forge running at low heat so you can try and maintain the blade at 1500F. Once the forge has been running at temp and is soaked, start "pumping" the blade in and out. The process will require watching the blade in the chamber for a good while, so wear the proper forge work protective UV/IR glasses ( AUR99 is what I use ). You push the blade through the forge until the tang is in the center, and pull it back until the tip is in the center. It takes time and getting a rhythm, but after a while, the whole blade can become evenly red. Have a friend help check with a magnet as it reaches non-magnetic. He should check at the mune, middle, and tip every few strokes. Once non-magnetic, really try hard for even color along the edge ( the spine is not as important). Heat about 50-75°F hotter than non-mag and immediately quench in the oil tank.
Tempering - The next thing that comes up is tempering a long blade. You can use your home oven and for some medium length blades put it in diagonally. On longer blades, place the blade in the oven with the excess sticking out of the top corner. The door will shut almost all the way. Fully pre-heat the oven and bake in this position for one hour at 450F. Turn it around and bake the part out of the oven for an hour. Cool off and repeat. Three tempers are a good idea when doing this method.
A couple tips on doing this:
Practice the quench and pumping with a sword-length bar of mild steel a few times to get it down before doing the actual sword blade. This will also warm the quench oil.
Pump faster in the middle of the blade and slower toward the ends so they spend about the same amount of time in the heat.
Use box jaw tongs with a keeper on the reins so you don't get hand cramps trying to grip the tongs too tight.
Go slow, and let the sword heat up slowly. The forge should be running at a low gas flow and whispering, not roaring.
This requires a full size forge. A paint can or other small forge won't work. The forge chamber will have to all get fully soaked and be glowing before you can do the pumping. Run the forge for 10-15 minutes at least. Obviously, the longer the forge the better, but a 14-16" forge can HT a 36" katana quite well with some practice.
Doing this at night or under shade on a cloudy day is best.
Silly as it sounds, make sure there is enough clearance over the quench tank to get the blade in. The tongs and blade can be over 50" long in many cases. Add that to a 40" or taller quench tank and you can't make a straight in plunge in some shops.
There can be considerable smoke and fire in a sword quench, do it outside if possible, and have the fire stuff and a hose handy.
