Tifouix Posted July 17, 2011 Share Posted July 17, 2011 Hello, In my country, no one answer that question. ( sorry my english is bad ). It 's about a propane forge, just one burner without turbo. I want to forge a knife, i 'd like to know the size of the home forge i need Thanks^^ Quote Link to comment Share on other sites More sharing options...
Backwoods Blacksmith Posted July 17, 2011 Share Posted July 17, 2011 Hello, In my country, no one answer that question. ( sorry my english is bad ). It 's about a propane forge, just one burner without turbo. I want to forge a knife, i 'd like to know the size of the home forge i need Thanks^^ Are going to use the forge only for blade work? I like the NC line of forges. No blowers and multipal burners. The Whisper Daddy is their large one, and they make a blade forge capable of welding with. A small single burner with a 6in interor and 12in long will work very nicely. Use two layers of Kaowool, altho one layer will work. Use brick to close up the back and front. I have made several of these and with mulitable burners. Run your gas pressure between 10 and 20 PSI. Once your temp comes up you will have trouble keeping up with more than three irons in the fire. Use your pressure gauge to control oxidation and heat. If you are not welding turn the heat down a little to keep the steel in the yellow range and not burn up pieces still in the forge as you work. I hope this helps Quote Link to comment Share on other sites More sharing options...
Tifouix Posted July 17, 2011 Author Share Posted July 17, 2011 Thanks for your answer, yes i'll just forge blades around 8 to 15in, so for home, 6in interior and 12in long are ok for this kind of blades with just one burner ? And if i use 3 or 4 layers of Kaowool and not 2 what happened ? Time to obtain good temperature is longer ? Thanks for all Quote Link to comment Share on other sites More sharing options...
pkrankow Posted July 17, 2011 Share Posted July 17, 2011 At some point extra ceramic wool does not make extra efficiency. 3 inches is considered overkill for a small forge, as 2 inches will allow the shell to stay cool enough to touch for several hours. Radiant loss out the openings becomes a bigger source of energy loss. If you put a door in the back you can work very long items, you can only work a small area at a time anyways. Phil Quote Link to comment Share on other sites More sharing options...
Tifouix Posted July 17, 2011 Author Share Posted July 17, 2011 I'll use this empty gas bottle for my forge, 13.78 inches long, 11 inches larg, and I'll put a system of door in the back. With 2 inches of ceramic wool, the remaining diameter of the home forge will be 7 inches, it's ok ? Or too important ? And sorry again for my english Thanks Gwen Quote Link to comment Share on other sites More sharing options...
Backwoods Blacksmith Posted July 17, 2011 Share Posted July 17, 2011 A door can limit your oppotions. The use of brick allows you to make your opening the size you need not the size of the door. Yes, you get some heat loss but not enough to cause concern. With the small chamber and two inchs of insulation one burner will do it. Once it comes up to heat you can adjust the gas pressure to control scale. With brick on each end you can heat longer pieces by passing them through the spaces in the brick. If you build a forge with a 10 inch chamber or larger and 18 inch long than you would want two burners or even three. My pipe forge was made from 12 in gas pipe and is 18 inchs long. I only have 1 inch of insulation so I have a 10 inch chamber. I found that to get the heat I wanted and to control scale I needed 3 burners. But I can forge weld big billits of material. Quote Link to comment Share on other sites More sharing options...
Tifouix Posted July 17, 2011 Author Share Posted July 17, 2011 What is the better line for the chamber, square, circle or oval ? Thanks Gwen Quote Link to comment Share on other sites More sharing options...
Backwoods Blacksmith Posted July 18, 2011 Share Posted July 18, 2011 I don't know that there is a difference. Once the chamber gets hot, it is hot everywhere. That is why it is important to have good insulation. To keep the heat even and on the inside. I am sure that someone has done tests to find the optimal shape, but I have made and used square, rectangle and round to good effect. I think that most of us use what we have available, but the commercial forges all seem to be square or rectangle. This may be for manufacturing purposes. Follow the threads on the forge forum and you will get more information than you know what to do with. My thoughts are to keep it simple. I still lean toward the NC Forge style burner design and I know that the blade makers really like them. Quote Link to comment Share on other sites More sharing options...
SamT Posted July 18, 2011 Share Posted July 18, 2011 Gwen, I didn't see it mentioned, but if that tank held any kind of pressurized fuel ie: propane or butane, make sure to fill it to the brim with water before cutting. I would leave it full of water while cutting it too. Can't be too careful with that cutting into a closed vessel that held fuel. Even an old oil barrel can explode due to fumes still in the container. If you cant get the valve off of the tank drill into the end with a holesaw and fill it that way, but be sure there is no pressure inside when you start to drill. Edit: Or is that what you were doing with the pump up sprayer? If so, carry on. :P Quote Link to comment Share on other sites More sharing options...
pkrankow Posted July 18, 2011 Share Posted July 18, 2011 I built an oval to reduce volume and have a large floor, but it would not heat evenly and was very expensive to feed propane. It was a 2 burner. I built a much smaller 1 burner and have much better results using it. It looks like a mailbox with an arched top and flat floor with hard corners. It also does not heat evenly, but it is less of an issue. The burner firing directly down on the flat floor causes a serious hot spot. Phil Quote Link to comment Share on other sites More sharing options...
SamT Posted July 18, 2011 Share Posted July 18, 2011 I wonder how a long, thin ribbon burner spanning the entire length of the forge would work. Should heat about as evenly as possible. Refractory cement is expensive to ship though if you can't find it locally. Quote Link to comment Share on other sites More sharing options...
Backwoods Blacksmith Posted July 18, 2011 Share Posted July 18, 2011 I think that the most efficient style I have made has been round with the blast coming from the side located in the upper third of the of the vessel. This seemed to cause the flame tocirculatee and spread. Thus no hot spot directly onto the floor. A point ofinterestt is that by putting a fire brick or refractory floor in the bottom the hot spot will spread and protect the softer Kaowool. I also use a dished stainless plate for fluxdrippingss when welding as the melted flux will eat the floor. Currently both of my gas forges [one square the other round] has the blast at the top and on center. the square forges chamber is 6in x 9in with a single burner and the other is round with a 10in x 18in chamber with 3 burners. The ends are closed up with fire brick so I can change the opening size to fit the work. If I need to heat a short section or make large scrolls or forms I still use my coal forge. This is what I started with in 1979 and am still most comfortable with. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted July 18, 2011 Share Posted July 18, 2011 The roof of the forge is often an arch so that the kaowool will support itself and not need to be fastened in some way. As the easy way to get an arched roof is to use a section of pipe or other round cross sectioned material propane forges are often round. As kaowool is quite soft, the floor of the forge is very often armored with a section of half thickness hard firebrick on top of the insulating kaowool. You don't need to heat more of the blade than you can forge at one time. Heating more than that just leads to scale losses, decarburization and grain growth. So even swords can be forged in a 12" long gas forge! The exception to this rule is when you heat treat and want the entire blade to be equally hot at the same time. Many knifemakers have a separate forge just for heat treat as the cost of building a forge is much less than the cost of paying for propane to heat a larger forge when working smaller items on a regular basis. A door system is a good idea and as mentioned some people use a stack of fire bricks for one that is easily made and easily configured for different jobs. I have a set of tongs that are sized to fit firebricks which is a useful tool to be able to move them around when hot. Quote Link to comment Share on other sites More sharing options...
Tifouix Posted July 18, 2011 Author Share Posted July 18, 2011 Gwen, I didn't see it mentioned, but if that tank held any kind of pressurized fuel ie: propane or butane, make sure to fill it to the brim with water before cutting. I would leave it full of water while cutting it too. Can't be too careful with that cutting into a closed vessel that held fuel. Even an old oil barrel can explode due to fumes still in the container. If you cant get the valve off of the tank drill into the end with a holesaw and fill it that way, but be sure there is no pressure inside when you start to drill. Edit: Or is that what you were doing with the pump up sprayer? If so, carry on. Yes exact, it what i was doing, now it's empty and i'm alive^^ Thanks for your answers, many things to read. I'll post after reading your posts Thanks again Gwen Quote Link to comment Share on other sites More sharing options...
Tifouix Posted July 18, 2011 Author Share Posted July 18, 2011 Backwoods, you have a photo of your 3 burners forge ? Quote Link to comment Share on other sites More sharing options...
Backwoods Blacksmith Posted July 22, 2011 Share Posted July 22, 2011 This is my large gas forge. 12" gas pipe 18" long. The ends are closed up using fire brick. This allows me to tailor the opening to fit the stock. I had used a 12 volt blower-burner but did not care for it. I have since added the 3 atmospheric burner set up from a NC Forge Whisper Daddy. It had been dropped when we moved and I have not gotten around to fixing it. There is a sliding rest in the front for longer stock. The stand is from Harbor Fright 29.99. I have welded stacked billets 1 1/2" by 1 1/2" Quote Link to comment Share on other sites More sharing options...
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