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Questions: Economical Tempering Oven, Forges


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I'm new around here, but have been lurking for a while. The wealth of information I have found here and on similar sites makes me think there is still hope for the internet. Anyway, I am an aspiring knifemaker, and have recentely taken to "upgrading" my equipment. I'm almost finished (I use the term loosley) with a power hammer build, Junk Yard Rusty style, and have aqquired the materials neccessary for the construction of a couple new forges. I am also going to attempt to construct a Tempering oven similar to the one built by Jesus Hernandez from this post: http://www.bladesmithsforum.com/index.php?showtopic=21489

My first questions are regarding the construction and possible improvement of his design. I want to build it on a much smaller scale, since I am nowhere near making a quality or even shabby sword at the moment. I have a propane tank that's about 1' diameter and about 22" Long. That is my
target oven size. I want to be able to temper around 10 large blades, or 20 or so smaller blades at a time, between 350-600 Degrees F. A toaster oven works fine for one or two blades, and so does the kitchen oven, however, running the kitchen oven for 4 hours or more for one or two blades eats propane pretty fast, and just seems un-economical to me. Plus I want something nearer to my work area, so I don't have to run inside.

My Questions are as follows:

1) From looking at the pictures, it appears that the burner is constructed using a Venturi type Burner design, which I believe is attached to an adjustable regulator (got one 0-30 psi), and a capped off piece of Pipe. Am I right ? Also, I've purchased a 3/4" venturi burner kit from HighTemp, and if I am correct I should in theory be able to simply connect the end of the Venturi Burner to a bell reducer or coupler, and then to a capped off 3/4" or 1" black iron pipe with holes drilled in it?

2) What size diameter should the pipe be if I am using a 3/4" Venturi burner for the body? 3/4", 1", larger? Again, my target size is a 22" long body, so probably 18"-20" long pipe will be needed inside the body of the oven, not counting the body for the venturi.

3) How big should the holes be drilled ? 1/16", 1/32", I imagine no bigger than 3/32" would be neccessary. Also, how far apart should they be ?
And is there a minimum number of holes? Propane can be scary, so I don't want to create a dangerous situation where I have to much pressure or anything like that. I like my eyebrows.

4) My plan is to add a 1" layer of Inswool, 1/4" satanite and itc-100 to the Oven body. Is this advisable ? Or is it un-neccessary ?

5) What about venting ? My plan was to leave one end of the propane tank closed/uncut to retain heat. But What about the front opening ?
Should I leave a Door off completeley ? I don't think leaving it closed would be a good thing, but what about say a 3"x3" Peep whole of sorts, cut into
the Door? Would that be adequate ?

6) I have some hard Firebrick that I was thinking of using as the floor. My reasoning is, if I have a firebrick floor, with the burner under it, but
leave 1"-3" of open space on the sides of the Firebrick Floor so the heat can rise, I should be able to get a stable heat combined with the Inswool and Satanite coating? Does that make sense ? Not gonna ask if I'm crazy :P

7) What is the Maxmimum pressure a Burner of this type can handle ? Again I don't want to create a dangerous situation, by accidentaly turning the regulator up to 30 psi. Would a 10 psi BBQ type regulator with a needle valve be a better option?

Regarding Forges:

I have a really nice 2 Venturi burner horizontal forge. I love it. Unfortunatley I've found that it can outwork me in a hurry, which becomes increasingly uneconomical. This led me to stop forging for a while and focus on building a Power Hammer. I really, really like welding Billets together. It's Fun. While my Rusty Style power hammer is Almost ready for it's first test run, it's capabilities are still questionable. Anyway, I've decided to build a couple forges. I want to build Don Fogg style Vertical forge, although a bit smaller. I have another standard #20 propane tank I think will work, or I have some 8" Diameter pipe that I just picked up from the scrap yard. The pipe however is painted with a thick layer of Red paint on the outside and black paint on inside. Not sure what it was used for, and also not sure if I should strip off the inside layer of paint. I imagine if a forge is constructed properly, this inside layer of paint can stay put. But then again, my first forge had a problem with hot gases escaping and getting inbetween the Forge shell and the Fiber blanket, causing the top of the Forge to reach cherry red heat. Apparently it was just damage caused during Shipping, and has since been fixed. I also want to build a small forge similar to Larry Zoellers Mini forge:


I have a Bernzomatic BZ8250 hose torch that I plan on using with the Mini Forge. And I'll probably get a hose and adapter so that I can hook it up
directly to a small BBQ propane tank. Also, I was going to use the 3/4" Venturi burner (or another one if the tempering oven works out) for the larger vertical forge. I've looked into blown burners, and I see the advantages, but the cost of supplies is prohibitive at the moment, atleast until I sell a few knives. So I will stick with the Venturi burners for now. Besides I have enough wires and hoses sprawled out around my small shop.

Some questions:

Regarding the Mini forge:

1) Has anyone built something like this ? What kind of performance can I expect with the torch burner (BZ8250)? I can't seem to find specs as to output of a small torch like this. I'll be using propane primarily, not MaPP Gas or the Propylene equivilant. It does have a spiral flame as opposed to a pencil torch flame.

2) Would adding a stainless steel flare to the end of the torch add any benifit at all ? Or is it simply un-necessary ?

3) Would a vertical forge setup using this torch be any more efficiant or powerful ?

4) Any ideas as to the maximum Volume I can possible heat with this torch? The specs on my 3/4" Venturi say around 350 Cubic Inches. I can't imagine more than half that for this particular torch.

I want to make this type of forge mostly so I have something portable for the road, and I don't expect it to do more than make small items such as
roses, RR spike letter openers, simple firepokers maybe, or lizards or small fun things like that.

My Current plan is use the 8" Diameter pipe for the Mini Forge, with two 1" layers of Inswool, 1/4" Satanite, and ITC-100. If my math is correct:
I can build small forge with an Inner Diameter of 4" and a Length/Height (depends how you look at it) of 8", would give me a Cylindrical volume of about 100.53 Cubic Inches. Or If I made it more rectangular, I can have the forge 4"x4" x 8" Long, and that would give me a volume of 128 Cubic Inches.

5) Is 100 Cubic Inches shooting to low or High for a small Torch like the BZ8250? I only need forging temperatures and don't expect to weld.

6) I'm thinking something like 3"x3" opening in the front and back for this type of forge. Is that too much ?

Sidenote: In an effort to not waste materials, I've made a small quick and dirty program to help me decide the best configuration for a specified Volume. Simply gives me the possible dimensional configurations for a target volume. Computers are better at math than I am.

Example output:
Cylinder Volume: 100.531 | Radius: 2.00" | Height: 8.00" | Diameter: 4.00"
Cylinder Volume: 153.938 | Radius: 3.50" | Height: 4.00" | Diameter: 7.00"
Rectangular Volume: 152 | Length: 9" | Width: 4" | Height: 4"
Rectangular Volume: 351 | Length: 6" | Width: 9" | Height: 6"
Rectangular Volume: 350 | Length: 7" | Width: 5" | Height: 10"
Rectangular Volume: 350 | Length: 7" | Width: 10" | Height: 5"
Cylinder Volume: 346.361 | Radius: 3.50" | Height: 9.00" | Diameter: 7.00"
Cylinder Volume: 351.858 | Radius: 4.00" | Height: 7.00" | Diameter: 8.00"
Cylinder Volume: 349.895 | Radius: 4.50" | Height: 5.50" | Diameter: 9.00"
Cylinder Volume: 353.429 | Radius: 5.00" | Height: 4.50" | Diameter: 10.00"
Cylinder Volume: 353.429 | Radius: 7.50" | Height: 2.00" | Diameter: 15.00"

Regarding the Vertical Forge, or General Forge construction:

I've been looking a lot at the various construction methods for a forge. It all seems pretty straight forward. Except I'm having trouble visualizing the proper,best, or simply effective method of constructing the Doors. I don't like the firebrick method, cuz stuff breaks easily around me. And as I have mentioned, I've had a problem with hot gases escaping into the forge shell before, so I'm concerned about that happening with anything I build.

With a horizontal forge:
I guess I could use firebricks. If I weld some plate to one side with a hole cut in it. It solves the problem for one side, as I can simply add the layer of InsWool. But the other side ? I don't want the Satanite coated inswool to be exposed if I can help it. Probably over worried and over thinking it. I have not built a forge before, and I want to keep it simple, but I also want to make the best use of the materials I paid for, and make a resiliant, long lasting forge.

With a Vertical forge:
On Don Fogg's Website, his vertical forge page says to simply cut a piece of metal plate or use an iron skillet for the top. LoL. So maybe I'm over thinking it. But wouldn't it be more efficiant to use more Ceramic Fiber Blanket with Satanite and ITC-100 ? How it would attach to the top is where I'm at a loss. I've seen hinged designs using a Castable Refractory like Mizzou's or similar. I've thought about making a round Lip of sorts that would fit the inside diameter of the 8" pipe and weld that to a plate, so I could just drop the plate on top, and the inside of that metal lip would be filled with either a Castable, or InsWool and ITC-100. Just worried about about the whole Hot Gases thing.

Sidenote: I do like the Super C forge.


I have some ITC-100 that has been sitting in my garage in a ziplock bag for like 2 years. The ziplock bag didn't work to well, so now the ITC has hardened into a nice little rock-like chunk. Can I still use it if I break it up and add some water ? I'm unsure of the shelf life the product. Recentley upgraded to TupperWare :)

Off Topic:

Words of Caution:

Welding Fumes are bad for you. Pnemonia Sux. In my case, one single Nut welded to a piece of pipe caused a lot of troubles. Even though I knew better, and should have spent 5 minutes setting up outside, I opted for lazyness and the 10 second weld. I don't care how tough you are or think you are, and I guarantee you that the Fumes won't care either. What's more worrysome than the Pnemonia is the possible cadmium exposure. Do yourselves are favor and think twice before you do what you do, because the work we do is dangerous. Zinc/Cadmium Fumes will put your pecker in the dirt quicker than my long a** post can bore you. The worst part is not being able to do what one truely enjoys doing. It's like being a Battlefield Soldier without his rifle. Sure you know what to do, and can talk a good game, but are ultimately ineffective. I see many people in videos and pics on websites, where knowledgable people skip simple saftey measures, like opening a door, or putting on a respirator or gloves when working with dangerous particles or fumes. And the dangers are usually understated. All it takes is one little fume cloud to perfectly roll up under your mask. Ask me how I know :P
Just something to think about for all the Noobs and Old Timers alike. Be Careful.

Picked up a 3M 6311 Respirator from Home Depot. Can anyone recommend a better one and where to purchase? Will be Used mostly for dust and grinding particulates. My new fan will conquer the smoke.

Sorry for the long boing post. Any help with any of my questions would be Greatly Appreciated.

Thanks For Your Time,


P.S.: Some Pics to offset the boring post.








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Is there some reason you're not using an electric kitchen oven. You can get nearly the whole temperature range you're looking for (600F might be a stretch, but you might get there with some extra insulation) and the size is good. I have one that I picked up on craigslist for $100. It's not pretty but is does a good job, and I can make tea, too :P .


I bought 3 or 4 cheap oven thermometers at the dollar store and I put one in each corner and calibrated it that way.


BTW, on a vertical forge you want to be able to get into the top for maintenance, so a fixed top is a pain. I stuffed the end of mine with a roll of Kaowool and threw a piece of plate over it with a brick to keep it from vibrating.



"The worst day smithing is better than the best day working for someone else."


I said that.


If a thing is worth doing, it is worth doing badly.

- - -G. K. Chesterton


So, just for the record: the fact that it does work still should not be taken as definitive proof that you are not crazy.


Grant Sarver

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Wow, never thought about that. That's a great Idea.


I do have a little toaster oven. And I will be using it. I just wanted something a little more controllable, and something I can stick in my shop that won't take up too much room. Electric is fine and good, but I do like the portability that propane offers. And I think maybe cheaper in the long run. I don't know, don't usually run much electric appliances out here in the Desert. The AC unit takes a toll by itselft.


A Million ways to skin a cat. Wish I thought of it, and now I'm jealous that I didn't. :)


I would love to have an electric kiln. And if I thought about it more before I spent all my money, I would probably have one. One of those nice evenheat kilns are definitely on my list. But in the mean time I need to make some knives and see if anybody wants them. I've looked around online, but haven't found one within my price range on the ebays, craigslists and others. I also have so many projects right now already backlogged that I simply cannot afford the time and resources on building one. Need to focus on what I can do, and what I have to work with.


If I do find an electric oven for $100, I might just sell some blood or kidneys for it.


As far as the vertical forge. Does seem like I've been overthinking it, I guess. Did you cover your roll of Kaowool with Satanite or a rigidizer of some sort ? To my understanding, when those ceramic blankets are used at high heats, without any form of covering, they realease some sort of Airborn silicate or something, that is really bad for the lungs. I'm a bit paranoid about such things at the moment.


That pipe I got from the scrap yard is 8" Diameter. Just about right for a vertical forge. I'm little worried about the paint though. I think I'll try to strip it off, but it seems to be on there pretty thick. If I build the thing right, I guess it can stay, not sure what kind of paint it is. I better shut up and stop being lazy and start stripping it. Probably better in the long run...


Thanks for the reply and idea :)



Edited by Bruno
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Bruno, if you lived close to me I have an old gas kitchen oven you could have cheap indeed. No electricity required, just need a regulator for 11"wc. I bet there is something similar near you.

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Thank you, I appreciate the offer. But the funny thing is, I already have 2 propane stoves. They just tend to use up a lot of propane which I use for cooking with aswell. Also, running them inside tends to heat up my whole house, which is not a problem in the winter, but not so good in the summer. My spare oven just takes up too much room to put in my shop/garage. And running it outside is not the best option in my opinion due to the wind and dust we get out here, also them darned free range cows like to destroy anything not covered in barbed wire (even that doesn't last long when they are thirsty). Don't really want a midnight Boom :). That's why I was looking to build a smaller tempering oven. More flexibility in terms of space and hopefully temperature control. Portability is always a plus too so I can drag it outside when needed.



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With a vertical forge. do you guys coat the entire top layer (under the top lid) of fiber blanket with satanite ? Front and back ? Or is just the hot side enough ? Probably just over thinking it again, just thought about escaping heat through any gaps that may be left between the inner layer and the top cover layer.



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I coat the hot side, that seems to do the job. I do think that you are over thinking all of this. There are two doors in the case, hot gases are going to escape there, not work their way through the blanket. The only reason I put a cover over the top is to keep any free fragments of the Kaowool from escaping into the air.


I like to have a 1/4 turn shutoff valve on all of my forges. That way, if something happens (and it never has, knock on wood) I can shut the forge down with a quick slap. A spray bottle of soapy water to check my fittings is my other safety tool, plus a fire extinguisher or two. One of the posters here, who's name shall be kept secret to preserve a bit of dignity, burned his shop down a few years ago. It wasn't his forge, but a spray of sparks from a grinder, which ignited a stack of hay. He got out ok, but lost pretty much everything.


Forges are dangerous, but mostly in the way that fire is. I always turn the fan on first, and have my lighter ready (propane plumbers torch) so there is no chance to build up a pocket of gas. The one time I did not follow that procedure gas pooled in the fan and when I started it up, WHOOOOMP, blew the fan case apart. It was a BTM (brown trouser moment). So be careful, but be not afraid.



"The worst day smithing is better than the best day working for someone else."


I said that.


If a thing is worth doing, it is worth doing badly.

- - -G. K. Chesterton


So, just for the record: the fact that it does work still should not be taken as definitive proof that you are not crazy.


Grant Sarver

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Thanks for the info. I do tend to either over-think things or not think at all on my bad days, probably just remnants from my programming days. I'm hoping to get started on it all real soon. Just giving the Pneumonia another few days. All this research is just making me impatient. With the 8" pipe that I have, I think I can make 3 forges out of it. 1 small horizontal and 1 small vertical using the Propane torch (just to see which works better), and one bigger Vertical using a 3/4 venturi. Along with finishing my power hammer and messing around with pipe burners, I have my work cut out for me. Hoping I can have some actual progress soon, without the BTM's :). Thanks again for the info and advice. If it wasn't for forums like these to bounce my random thoughts, I would probably have lost my mind weeks ago :unsure::blink: , Sure miss the Fire...



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