How Far Should I Go?

And I heat up a little and do it again. we have the highest electricity maybe in the USA. I live on Molokai HI. a kilm and oven would kill me. the wood I use is like mesquite burns hot and the coals last for ever.
 
Seedy Lot said:
Doing a search on the subject within this form it seems for oil hardening steels 1mm is probably a good safe bet. If you want to find out what the limit is grind thinner until you experience bacon edge then you will know for your situation what you can get away with.
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Been there. At that point you might as well throw the knife away, and start on a new one.
 
Britt_Askew said:
I'll take your word for it if you say you can hold at 400 degrees for 2 hours , but I'll be honest you would have won every dollar I had in my pocket.
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Yeah … this is real. Ive been looking at building a wood fired oven for baking hearth breads, pizzas, and other general cooking/baking. These ovens, especially the bigger ones, have a LOT of thermal mass, and stay hot a long time after the fire is out and the entrance is closed up.

In fact, for bread baking, the intent is that the oven is fired for a couple (or more) hours, then the spent ash is swept out, the floor mopped clean, then the thing is closed up to allow the temp to cool just a little and for the temperature to equilibrate across the floor. Once that is done, you can bake many (dozens) of loaves of bread in many batches and the oven still stays hot enough to do that.

Ive seen data taken from one oven that had the oven one evening fired to about 850 F to cook pizza. Closed up overnight, the oven was down to about 450-500 mid day the next day to cook hearth bread. The NEXT morning it was down to about 300-350 to do more general regular temperature baking/casserole type cooking. I am *hoping* that with my move to louisville next summer i will be able to put in one of these ovens.

Given the steadiness and uniformity of heat in these ovens (and the ability to accurately read the floor temperature with an IR thermometer), they would be great for tempering. BUT because it takes time to hit the right temp, if the tempering job is time sensitive, getting that timing right might be a little challenging.
 
Yes, most of the time its too hot to start with. If I knock the coals around it kinda settles it down. as the temp drops I put the knives in at about 475dg or less and close it up. sometimes the temp will go up some, you'll know in about 10min. but 2hr later its still at 400dg. I take the knives out and let the cool and add a little more wood to the fire. 20min later put them back in for 2hr. I guess it works? one of my first knives I dropped on the floor before tempering, it split in half. I guess it needed tempering.
 
it was made with Perlite a little sand and cement the floor is about 2in thick and walls 1 1/2-2in. I made the oven first over a chicken wire and plywood frame and then made the bottom. I just lifted the oven and set It on the bottom and sealed with silicone . its got a few cracks in it and I sealed with silicone. it rains a bit here and when starting it up it takes a bit of time to dry it all out.
 
Britt_Askew said:
I'll take your word for it if you say you can hold at 400 degrees for 2 hours , but I'll be honest you would have won every dollar I had in my pocket.
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Makes sense. You have a smaller beehive oven. The data i quoted was for, i think, a 40 inch double insulated build that also had an outer masonry shell. Those babys stay hot for DAYS…
 
docmott said:
I'll try and post a few pics
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Nice oven. Winter storm here in MN today. Good day to be inside and bake …. So just started up a loaf of sourdough bread. Could use an oven like that to bake it. But wait, it IS snowing outside 😒
 
Cushing after reading your post I was thinking yep I'da lost my money but then docmott says he puts blades in at 475 , so temp ranges 475 to 400. That's not holding 400 for 2 hours in my eyes , to much temp variation.
Like Stacy said the cost of actually running an electric oven even with high electric cost is not much per blade. If you heat treat multiple blades each time you turned oven on it would be even cheaper. Electric oven for the win.
If you want a cheap option for an electric tempering oven there are some here that use a modified toaster oven, a forum search should give you some ideas.
 
Britt_Askew said:
Cushing after reading your post I was thinking yep I'da lost my money but then docmott says he puts blades in at 475 , so temp ranges 475 to 400. That's not holding 400 for 2 hours in my eyes , to much temp variation.
Like Stacy said the cost of actually running an electric oven even with high electric cost is not much per blade. If you heat treat multiple blades each time you turned oven on it would be even cheaper. Electric oven for the win.
If you want a cheap option for an electric tempering oven there are some here that use a modified toaster oven, a forum search should give you some ideas.
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If you please look again at my post .... I was talking about (and citing data from) somewhat bigger ovens .... mostly just trying to make the case that what docmott is saying is not totally out of the question. I do agree that his smaller "beehive" design oven looses heat faster .

The argument about electricity use might be correct .... but it might just be that he wants to try it this way ..... and I personally feel we should not actively dissuade him. Lets see how good the result is, and especially whether it is good enough for him and his needs in the end.
 
Britt_Askew said:
Cushing after reading your post I was thinking yep I'da lost my money but then docmott says he puts blades in at 475 , so temp ranges 475 to 400. That's not holding 400 for 2 hours in my eyes , to much temp variation.
Like Stacy said the cost of actually running an electric oven even with high electric cost is not much per blade. If you heat treat multiple blades each time you turned oven on it would be even cheaper. Electric oven for the win.
If you want a cheap option for an electric tempering oven there are some here that use a modified toaster oven, a forum search should give you some ideas.
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actually, with the basic design of his current oven, he could take the dome off the base, add a layer of refractory brick, put the dome back on, then cover the dome in a layer of refractory blanket with stucco on the outside. my guess is that *that* oven would then cool much slower than the current one.
 
Cushing H. said:
If you please look again at my post .... I was talking about (and citing data from) somewhat bigger ovens
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I got that

Cushing H. said:
The argument about electricity use might be correct .... but it might just be that he wants to try it this way ..... and I personally feel we should not actively dissuade him.
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He can do it any way he wants and I am going to sleep the same. The way I read it though the reason he wasnt using electricity was he thought it would be real expensive per blade, even with high electric cost thats just not true. I always thought shop talk was about helping people make the best blade possible , if you read a thread tomorrow where somebody is asking how to temper a blade would you ever recommend doing it in an oven with a 75 degree temp swing while tempering ??
And a toaster oven will probably be alot cheaper than
"he could take the dome off the base, add a layer of refractory brick, put the dome back on, then cover the dome in a layer of refractory blanket with stucco on the outside"
 
so far ive done 2 batches of knives in the oven. the first was kinda learning, I wasn't sure what was going to happen. the first attempt I made the temp a little high expecting it to lower some. it didnt. so first batch and 2nd tempering I let it cool to a hair over 400dg. closed it up and checked every 20min or so. after 2hr the temp was just the same. I guess it works. on the 2nd batch of knives I let the fire kool to just over 400dg. put them in and closed it up. I checked every 20min or so. all fine. after 2hr I pull them out to cool. put a little wood in the fire, it didnt take much and it was up to 600dg. I busted it up and let it go about 20min and it was down to 400dg. put them in and closed the door. the temp went up a little? not over 450dg so I just opened the door and let it go down to 400dg. closed the door and checked every 20min, it stayed there until 2hrs was up. im just figuring it out. I think the is the rate. for KWH $38.84
 
Docmott just to be clear , I am not saying what you are doing is wrong
 
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