Wood Fire Tempering Oven

[Jay.bro]

I was perusing the threads of the heat treating discussions and I have yet to come across a thread about this. I am considering the possibility of creating a wood fired tempering oven similar to a small outdoor brick pizza oven. Has anyone on here ever experimented with such a project and if so what were your results and could you comment your pictures on this thread? My main concerns are that there would be too inconsistent of a heat for tempering and that the oven wouldn't maintain the heat long enough to get a proper temper. Thanks in advance and happy forging.

[JHCC]

With so many other more consistent, predictable, and reliable methods available, I'm wondering why you'd bother?

[Jay.bro]

This is mostly an educational inquiry since I see people mentioning how others have it much harder than so many of us and I was thinking from a bare minimum ideology it could potentially be a tempering solution for someone lacking a power source in their smithy or someone that wants their work to be completely done by hand with no electricity involved. I also have yet to find any reference to this idea anywhere and I see ppl mentioning using their ovens to temper quite often I just look at it as taking the more of a luxury technology out of the equation 

[Charles R. Stevens]

I would imagine if one heated it and waited for the temp to drop to the temp one needed it might work, keeping it at the right temp wit live fire would be a real bear. But heating it like a bread oven (you do flat breads first as the oven is typically to hot for bread at first) then put your tool in on the falling heat it might work. Historically either burning off oil with the appropriate flashpoint 3 or more times worked, as did polishing the blade and watching the colors run (either from internal heat from the non quenched area or an exterior source as the forge fire or a heated iron or tongs) very simple technology and a lot of skill made tools in the day.

[JHCC]

I've seen video of Japanese smiths sprinkling water droplets on their blades and observing the presence and vigor of the Leidenfrost effect as a gauge of the tempering heat.

[Jay.bro]

That's interesting I hadnt thought about the polishing one I'd seen a few things on YouTube about using the oil method but I've come to trust very little I see on YouTube from many of the comments I've read on IFI about the ones that claim to know what they are doing but really have no clue and how a lot of new smiths are being misled by these people

[Steve Sells]

For swords I use my BBQ and small amount of charcoal, with digital thermometer to monitor temperatures.  adding or removing coals as needed, raw wood seems to need a large amount of mass to keep burning

[Latticino]

1 hour ago, Steve Sells said:

large amount of mass

From a theoretical standpoint if you were in medium to large scale production on a shoestring, building a wood fired oven for tempering might not be too much trouble if you had significant thermal mass in its construction as well.  That will tend to smooth out the temperature deviations as the firing rate of your heat source changes.  Not necessarily an efficient way to do things for a hobbyist, but perhaps it could be scaled down.

Personally I'm with JHCC on this one.  Other alternatives are easier to control and operate.

[Jay.bro]

I actually hadn't thought about the mass it would take of wood but in the theory of the brick pizza/bread oven style wouldn't it be doable to use charcoal in it as well seeing as how it's being used as a tempering oven and not for actual baking or anything like that. This is all hypothetical I'm just trying to see how this idea I had considered once before could play out.

[Charles R. Stevens]

Brick ovens work in mass if masonry not wood, you build a fire in it and let it burn for an hour or so, remove the coals, close it up and wait for another hour or so then you use the stored heat in the masonry (or adobe) mass

[Jay.bro]

Oh okay that's pretty cool I had made plans for this awhile back right after I got my forge since I use wood as fuel and I got to thinking if I did a lot of stuff like chisels punches and drifts all in one day then in theory that would've worked better than having my oven running all day in the house I know there are several different methods but the oven was the most common I'd read and I got to thinking about making an Adobe brick wood fired oven since its what I use in my forge and use that when I wanted to temper a lot of things at once I have since thought more into a thrift store toaster oven but wanted to see if my original idea had any validity as a good idea

[Charles R. Stevens]

A block of red hot steel or a gentle charcoal fire the gently roast the tool over wile observing the oxidation colors is still practical for chisels and punches, as is quenching the cutting edge, polishing it and turning th tool struck end down and letting th heat in the that end of the tool rise. With the exception of stone masons tools most struck tools are relatively soft on the struck end so quenching the entire tool may not be desirable, or if the entire tool is quenched, heating the struck end in a gentile fire and letting the colors run works well. Oxidation colors are fairly accurate as to temp, but due to the nature of different alloys they may not be for hardness. Some times one will have to re heat treat or draw more temper on a tool, as some steels will be to soft or two hard for your intended use at the same color. 

[Jay.bro]

Okay so basically the k.i.s.s. method applies here instead of doing a ton of work building the oven and getting it going I can actually just use my forge to temper most things then I presume? For instance as my fire sits without the blower I can use that bed of coals to temper most things I need to by watching the oxidation colors?

[JHCC]

Basically, yes.

[Frosty]

Yes, KISS it. I used to temper tools by shining them up, laying them on a red hot steel bar and watching the colors run. Another method I messed with a bit was to heat sand in a bucket and lay tools in or on the sand to temper. I figure it'd work a treat but would take a lot more technique development than I put into it. When I was a field guy I did a lot of smithing in the camp fire while the other drillers were knocking back a couple half racks apiece. I'm not much of a drinker and needed something to do other than read.

Anyway, I used to do a lot of playing in camp fires and have used all sorts of stuff to heat treat . . . things. You can: Draw a tool back and forth between a couple of hot rocks, Lay it on the ashes  next to or really  close the fire, Rake coals out to make a tempering fire, Rake the fire off the dirt or sand it's built on and lay the tool there, etc. 

Oh and as a non blacksmithing aside. Heating a bucket of sand to a reasonable temp and putting some in a sample bag beats heating rocks to keep your feet warm on cold nights. By cold I mean Alaskan late fall or early spring cold in the interior, sub zero, sometimes frighteningly serious sub zero. The coldest documented was -40 f. If you have good gear sleeping warm isn't a problem, it's getting up in the morning that has you shivering.

Frosty The Lucky.

[Charles R. Stevens]

And getting warmed up before crawling in bed. If you are already chilled it takes a heck of a long time to get your hands and feet warmed back up. If your hand and feet are cold a hat and an extra layer on your torso is in order. Lol

 

[JHCC]

Nothing beats a good chunk of soapstone for slow release of heat.