Rob N. Posted November 7, 2011 Share Posted November 7, 2011 Ok, so I'm making a heat treat forge, based on Jesus Hernandez's hot water tank HT forge. I had access to an old 50 gallon gas water tank, so I started to rip that bad boy apart to get to the tank. The tank is a lot bigger than I thought. After cutting the long 4 inch pipe out of the belly of the beast, I have an approximately 40 inch by 17.75 inch steel tube. I am planning on reusing the ends of the tank as I know they'll fit I was also planning on lining the tank with two inches of Kaowool and a coating of either Plistix alone or a castable (such as cast-o-lite) with the plistix on top. I plan on having my forge vertical as opposed to horizontal like Jesus' forge. Why? Because when I get better at this smithing gig, I do want to make bigger blades, and from what I've read, taking a 30+ inch blade at 1500 degrees out of a horizontal forge to the quench is tricky indeed. The steel bending, etc...Or is that overblown? Anyhow, my question to the experts here is where would be a good place to set my burner inlets? Can I get a way with just one? Or, given the size of the forge, should I have at least two burners? In my novice estimation, I'm figuring I need at least two, so the question again is where to put them? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
MattBower Posted November 7, 2011 Share Posted November 7, 2011 As far as I know, Jesus's HT forge is based on Don Fogg's drum design. (It looks very similar, and I think Don's came first, so . . . ) The reason for the horizontal orientation is that if you make it vertical, you set up thermal gradients in the forge -- hotter at the top, cooler at the bottom. (Salt pots are vertical, of course, but salts conduct heat so well that this isn't really a problem.) You want the whole blade at an even temp for the quench, and that pretty much dictates a horizontal orientation. If you look at Don's page on his HT forge, you can see that he put in internal supports for the blade to rest on while it's heating. These forges are not designed to get terribly hot; they're designed to achieve an even, controllable, relatively low temperature. (1500ish degrees F) That's why they only use one burner. And the orientation of that burner -- firing down the length of the forge, coming in along the bottom -- is an important feature. You'll also note that Don and Jesus both use only one layer of Kaowool. Again, this thing isn't designed to weld -- it's designed to maintain a nice, even temperature around 1500 degrees F. This type of forge -- furnace would be a better word -- isn't expected to encounter the abuse that a normal forge does. Temperatures will be relatively low and there should be no flux or mechanical wear to speak of. So the sealing coat over the blanket only needs to keep in the fibers -- nothing more. I'd suggest keeping any coating on the wool to an absolute minimum. If you add thermal mass in the form of dense refractories (even "lightweight" refractories like Kast-O-Lite), initial heat-up and subsequent temperature adjustments will only take longer. If you aren't planning on doing big blades for a while, you might want to start with a scaled-down version that's appropriate for the work you're currently doing. It'd be less expensive to build and run, and it'd be a much cheaper way to make any mistakes that you may end up making. Quote Link to comment Share on other sites More sharing options...
Rob N. Posted November 7, 2011 Author Share Posted November 7, 2011 Thanks, Matt for the reply. I wasn't sure if I was over doing it with the two inches of kaowool, cast-o-lite and plistix or not. Sounds like, for a HT forge, I would have been. Thanks for setting me straight. As far as building a smaller one, that has definitely crossed my mind, however, I have this thing and I at least want to build it. I'll think of it as planning for the future. I have something else that might make a very good smaller HT forge for smaller pieces. In regards to the internal supports, I've spoken via email with Mr. Hernandez and he stated that he put rebar welded to the top of the HT forge to hold his pieces. That was an option for me, too. I do, however, still have the 4" inch pipe that ran down the middle of the tank. I was thinking of cutting that down to size and using that as the internal support (i.e. putting the blade to be heat treated in the pipe for nice even heating). The pipe would be suspended with either rebar or some other steel. As for the burner, I was thinking of using the same T-Rex that Mr. Hernandez uses. Quote Link to comment Share on other sites More sharing options...
MattBower Posted November 7, 2011 Share Posted November 7, 2011 Well, if you stick with a design that's already working for Jesus, I doubt you'll go far wrong. The tube down the center will probably work. (And it could have an advantage -- you can stuff some charcoal down it to maintain a nice reducing atmosphere around the blade as it heats.) Expect that tube to eventually burn out; i.e., don't make it too difficult for yourself to get back inside the furnace later and make repairs. Quote Link to comment Share on other sites More sharing options...
Rob N. Posted November 7, 2011 Author Share Posted November 7, 2011 Thanks. Like, Jesus, I'll just have the ends tack welded for easy unassembly. The flue, I'm guessing is just a mild steel? I suppose Stainless would be ideal, but hey I have it and it's free. Thanks again. Quote Link to comment Share on other sites More sharing options...
MattBower Posted November 7, 2011 Share Posted November 7, 2011 I assume it's mild. I've never looked at one up close. The insides of water heaters definitely aren't stainless in my experience, so I assume the tube won't be, either. Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted November 7, 2011 Share Posted November 7, 2011 I am not sure how much blade work you have done up to this point but one thing Matt said that I will repeat as it is worth the effort! build a small gasser for making blades and gaining skills. You will learn a ton from that and Then when it comes time yoiu can use wot you learned for building large. One thing I see in this forum repeated over and over is folks seem to want to jump ahead too fast and not gain the basics that will allow them to move forward progressively, Most of the time this ends up with at the best they have to step back and learn from the bottom and at the worst they just move away from wot theyh wanted to do but became frustrated. If this does not apply to you and youi have a lot of expeerience with hammer and steel, in addition to all the other items needed for blade work then pass it by and don't feel badly towards me for bringing it up. Maybe someone else reading this will benefit. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted November 7, 2011 Share Posted November 7, 2011 The more insulation the cheaper to run. The only professional swordsmith whose shop I have spent time in had a custom built vertical HT furnace, electrical with ramping controls and an inert gas purge. Helped a lot for high alloy blades! Quote Link to comment Share on other sites More sharing options...
Rob N. Posted November 7, 2011 Author Share Posted November 7, 2011 Thanks for the advice, Rich. No, I don't have too much experience smithing. However, as I said to Matt, I have the parts (all free), I have the desire, all me, and I have the drive. I have stuff to build a smaller HT furnace and will, because as you inferred, I will be working with smaller pieces that obviously do not need a large HT furnace. However, I love fabricating, so I definitely will make the larger one, too. Thomas, in your opinion, should I put two layers of kaowool instead of one? As I told Matt, I am concerned about efficiency, obviously. He makes great points in that maybe the refractory and the Plistix may be overkill. I've got enough kaowool for two layers, so cost isn't an issue. Thanks in advance. Quote Link to comment Share on other sites More sharing options...
MattBower Posted November 8, 2011 Share Posted November 8, 2011 Extra insulation will certainly help with fuel efficiency. BUT, I think the theory behind how these things work is that the large interior volume helps reduce hot spots. Will one extra layer of Kaowool screw that up? Probably not. But I don't know for sure. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted November 8, 2011 Share Posted November 8, 2011 If you have the space I would go with 2 layers, but Matt has a good point. Quote Link to comment Share on other sites More sharing options...
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