I am starting a new project soon, a hand and a half knights templar with a 30" blade and a fuller. With the tang it will be 39". This is to long for my oven so I am thinking of tempering using 2 short sections of 1" round stock and holding them into the fuller while hot. Has any one used this method before or should I just build a tempering oven?

Search the site for "tempering tongs".

Also, the Knights Templar were a military order who used a lot of different swords at various points and places in their history. Do you have a number from the Oakshott typology that corresponds to the sword that you're making?

Method been in use for decades if not centuries.

The typology would be an XIIIa. A hand and a half, 30" blade, 39 o.a.l., with a fuller running down 2/3 of the blade. Im planning on forging in the fuller using 1" round stock for the dies, and for the tempering tongs. Im hopeing to blue the spine while getting the edge to a straw color. I have some experience in chasing colors, but not on a double edged sword and not of this length. Any advice? Or flaws in my plan?

Any possibility of doing a snap temper to straw on the whole blade and then go back and draw the fuller to blue; perhaps even with the straw edges in water soaked sponges?

Swords are scary when hard and brittle as a minor accident can result in catastrophic failure.

A snap temper is possible but only if i can figure how to do it in hot oil. I have not had good luck with this method as it always seems to draw the hardness back too far. Any advice would be helpful in regards to tempering in oil.

Biggest problem is to get the oil uniformly heated and measuring that heat. Convection usually causes hot and cold areas.

Maybe an oil-compatible immersion circulator?

then there is the issue of currents causing warpage

I've heard of that for quenching, but is it still a concern for tempering?

Usually no but this seemed to be getting into  Austempering, which is quench and tempering in same fluid heated to tempering temperatures so it cools then starts tempering in one operation basically forming bainite <over simplified> 

Thanks for the clarification.

That may explain why my first swords heat treat was so odd. After two failed tempering attempts I let the oil cool to 150 F, heated the blade to about 1650 F and held it in the oil a good 30 seconds, when it cooled, a file wouldnt touch it and it flexed nicely. It seemed to already be tempered. After testing extensively I did eventually do an oven temper, for good measure.

Are you confusing hardening with tempering?  Did you normalize first?   Multiple steps to heat treating! (And each has a specific name and process)

I did normalize first, and hardened two seprate times but both times when I tried to temper in oil it overdrew the hardness to the point where the blade would no longer flex but would bend. The oil was only 325 F, forcing me to abandon my approach. I do know the heat treat process, but i am still learning the science behind it.

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This link best describes austempering. I believe this best describes my last heat treat. I may have found my new favorite meathod, but further testing will need to be done. I do like the idea of quenching and tempering in one opperation.

That material is already covered in the pinned thread on heat treating

there is absolutly no problem in  tempering in oil or low temp salts from a technical POV. there is no reason that oil would over temper a blade at a gvien temperature and one of the reasons to use oil or salts is that they do circulate thus regulating the temperature. I have done over a hundred swords this way. you will need a thermocouple of some kind though.

If somthing is going wrong I would look at your overall HT.  also check for decarb that can lead to soft outsides on the blade causing a file to bite into the skin and a blade to take a set rather than springing back a little  post HT grinding can remedy this.

the currents causing warpage in tempering ??? never heard of that but sword blades do move whenever heated or cooled.

A word of warning though. hot oil or salts are potentialy dangerous and I have had a couple of tubes of 250C oil boil up out of the tube because of moisture in emulsified oil on a blade and cool oil on a blade going into hot oil....I no longer use this technique for that reason.  so be carefull and do your research.

Thank you basher that was very helpful, and yes, I will be doing more research along with testing.

I was referring to the current during the quench phase, things dont always come out correctly