northboundtrain Posted August 13, 2006 Share Posted August 13, 2006 Hey all, I built this forge originally to heat treat some woodworking plane irons that I made (not forged). It worked great, and the plane irons are far superior to anything that I've ever used. But in doing the research for heat treating, I inevitably read a lot of really cool stuff about blacksmithing in general, and now I want to use my forge for making forged knives. Here's my problem: This little forge doesn't quite get as hot as I think it should. I've read that propane forges should easily get hot enough to melt steel, but this one doesn't. It gets the steel to a bright orange, but not the yellowish almost white heat that would probably make my blacksmithing a little (lot?) easier. I'm having particular trouble trying to do any kind of upsetting operation. Here are the details of this forge: -Fire brick enclosure -#64 or 65 orfice (I can't remember which) -I'm running about 15 lbs of pressure, but whether it's 10 lbs or 25 lbs doesn't seem to matter much -The forced air source is compressed air operable by a valve. This gives me very good control, but I don't think it is a great long-term solution because it taxes my compressor pretty hard. The forge draws enough air on it's own to make a good bright cherry heat. Turning on the air changes the flame from blue to purple and makes the steel go another shade hotter. The pictures should clarify my description. The pic of the forge in use show the maximum heat I'm able to obtain -- shot in the daytime in slightly overcast conditions. So should I be able to get the steel hotter than this? Any feedback and critiques on the design of my forge are greatly appreciated. Thanks Hopefully, my posting of the photos works. Sorry for the size, I need to figure out how to reformat my camera.http://www.iforgeiron.com/gallery/showphoto.php/photo/754/cat/500http://www.iforgeiron.com/gallery/showphoto.php/photo/755/cat/500http://www.iforgeiron.com/gallery/showphoto.php/photo/756/cat/500 Quote Link to comment Share on other sites More sharing options...
Archie Zietman Posted August 13, 2006 Share Posted August 13, 2006 I'm no gas forge expert, but it looks to me like you need a much larger burner, or a much smaller forge box/body/whatever. You need to have them matched in size so that the refractory on the walls glows. Then you will be able to get decent heats. Also, when you make the chamber much smaller, open up the back wall a bit to allow for your work to be slid through to head the middles of longer bars. And, a cylindrical forge body would mean that the forge heats quicker/much more evenly and that you don't waste fuel and btus heating the corner s and that huge space beneath your piece there etc. so my $0.02 Smaller cylindrical forge chamber. ALSO: google Ron Reill gas forges, he has tons of info on gas forge design and fabrication etc. take a long look at all his pages. Quote Link to comment Share on other sites More sharing options...
northboundtrain Posted August 13, 2006 Author Share Posted August 13, 2006 I'm no gas forge expert, but it looks to me like you need a much larger burner. When you say larger burner, do you mean a larger orfice size? Quote Link to comment Share on other sites More sharing options...
Archie Zietman Posted August 13, 2006 Share Posted August 13, 2006 larger orifice with more fuel and air burning to make more heat go into the forge. I'm no expert though, you should really look at Ron Reill's gas forge pages.Forge and Burner Design Page #1 Quote Link to comment Share on other sites More sharing options...
polarbearforge Posted August 13, 2006 Share Posted August 13, 2006 I've built a number of forges, mainly with some aspect of bladesmithing in mind. I favor a round forge chamber to maximize swirl. The burner arrangement is different. I'm not sure I'd want it coming up from the bottom like that. It does seem that a bit of a chimney effect would happen and a lot of the heat would just go out the opening. I'm probably just missing it, but where does the gas hookup in the second picture? I can see the air connection, but I'm missing the gas. Gas forges are definately capable of getting hot enough to melt steel. My first forge (which was too big to general bladesmithing) would melt steel if I wasn't careful, and that was at 7 pound of pressure. It was a forced air burner. My small portable forge that I use for demos is a venturi. The first one would keep a real nice forging heat at about 1 1/2 pound of pressure and forge weld at about 4. The current one isn't quite the same, and still needs some tweaking. Ron Reils forge burner page is a really good reference. The venturi burners I use can be found at Propane Forge Burner Design / Sidearm Burners Jamie Quote Link to comment Share on other sites More sharing options...
northboundtrain Posted August 13, 2006 Author Share Posted August 13, 2006 I initially had the burner coming in from the side, but I changed that because it seemed like it was hard to get an even heat on the material. I'm going to pack out the inside of the forge with more fire brick to make it smaller and see if that helps. I'm also going to make the openning smaller and make a small hole in the back for longer material. Thanks for the tips, I'll keep you posted. Quote Link to comment Share on other sites More sharing options...
northboundtrain Posted August 14, 2006 Author Share Posted August 14, 2006 Update: I packed out the inside of the forge with firebrick. It helped maybe a little but not enough. Then I went out and got some drill bits: #62, #60, and #58. I'll try enlarging the orfice incrimentally and see what happens. I also bought a 4" duct fan that I will install on the air intake. The compressor set up does not allow for continuous forced air (the compressor would run constantly which it is not designed to do). So here's a question: If I feel like I should be wearing ear plugs while hammering (because I'm getting a loud sharp ring) does that mean that the metal isn't hot enough? Quote Link to comment Share on other sites More sharing options...
Archie Zietman Posted August 14, 2006 Share Posted August 14, 2006 Not in my experience. I wear those big earmuff things whenever I'm forging, and it really helps with noise. Earplugs work too. My humble opinion on the subject of heats: If you're getting the metal to orange or yellow heat, or just when it moves easily under the hammer, it is hot enough. It is much easier to move metal screaming hot IMHO (yellow heats move steel like butter), and once you're at a dull red heat, you might as well keep that heat in the steel and shove it back in the fire to heat up. If you beat that metal, it won't move much, so you might as well save your energy and spend the time and use the heat in the metal to help get you to orange or yellow when it will move eaier. You will save energy this way I have found. Happy Hammering, Archie Quote Link to comment Share on other sites More sharing options...
northboundtrain Posted August 27, 2006 Author Share Posted August 27, 2006 Well, my forge is working much better. I added more brick to the inside to make the firebox smaller, and the biggest improvement was getting rid of the burner grill and just having a nice big hole. The problem was that the fire was blowing itself out with the LP pressure turned up too high or the blower going too much. I think the grill messed with the flame and air flow. Now I can run higher pressure and more air. Increasing the orfice size was counterproductive; it made the flame blow out more easily. I welded the hole shut and went back to #65. Hopefully, I'll have some knives to show soon. Quote Link to comment Share on other sites More sharing options...
Sam Salvati Posted August 27, 2006 Share Posted August 27, 2006 Nice Rebar Tongs!!!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
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