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Posted by Trevor Jones on May 31, 2007, 8:54 am
Please log in for more thread options Prometheus wrote:
> Hello all,
>
> While my gas forge is very nice, and does the job well, I am
> discovering that using it is just way, way too hot for the summertime,
> even with vent fans right above it- it's like pointing a jet heater at
> myself!
>
> As I recently joined the local blacksmithing club, I now have a source
> for good coal, and I'm thinking that this may be the way to go for
> summertime use- from what I've observed, they tend to be quite a lot
> cooler than a forced-sir propane rig unless you're right next to them.
>
> So here's the deal- I can make just about anything out of sheet goods,
> bar stock or tubing. I don't have a cupola (yet), so casting iron is
> out of the question for now. I have a very lenient employer that
> allows us to use materials, within reason, for personal projects- and
> I also have a bit of stainless steel that I bought a while back
> availible for whatever I need. I've got access to all sorts of
> industrial-grade toys for building this sucker, so that is what I'm
> going to do.
>
> But, since I enjoy having the flexibility to make things that I need,
> I try to make sure that I use as little time and material as possible
> when doing government work. That's the point of this post- I already
> know how to overbuild just fine, but I need to figure out what I can
> get away with without sacrificing quality.
>
> I will be fabricating the firepot, grate, clinker breaker, and table
> from stainless steel, unless there is a good reason not to do so.
> Commonly availible sizes range from 16ga to 7ga (.063"-.188" nom.)
> While thicker may be better, it represents a signifigant increase in
> difficulty and cut time on the laser to use a thicker material. One of
> the guys I work with has a bit of stainless tubing that he estimates
> is about as thick as 12 ga sheet metal (.105") that is about the size
> of a coffee can that he is willing to give me, as he has no real use
> for it. I am considering using this for a firepot, if it is thick
> enough.
>
> But there's the trouble- there is plenty of information regarding cast
> iron coal forges, but I have seen very little about any made from
> stainless steel. What I need to figure out is what material I need to
> have to make decent parts that will hold up to the application.
>
> What I have in mind, if it will work, is 12 ga tubing for the firepot,
> a laser-cut 7ga grate, a 12-10ga table with a 1-2" lip around the
> edge, and an 11 ga clinker breaker. The blower piping will most
> likely be black iron pipe from the hardware store, though it may be
> stainless or 4140 depending on what we have floating around in the
> back shop where we keep tubing and bar stock.
>
> Any comments on this would be welcome- I have worked with stainless
> steel quite a bit, but that has never included working with it at a
> high temperature. If I use mild steel, I can build up to .25" thick,
> or thicker if I make a square firepot rather than a round one (though
> that would require a little shopping, and would delay the project.)
> If the 12ga firepot is way too thin, there is a possibility that I can
> get it step bent from thicker material in two half circles and weld it
> together, but that is a reasonably signifigant investment of the brake
> operator's time, and I'd like to avoid it if the thinner firepot will
> work. In a worst-case senario, I'll track down some cast iron pipe,
> but I'd just as soon use the stainless. While we have some other
> grades, I will be using 304- that's the common stuff, and it's less
> expensive than some of the other materials.
>
> We're kind of in a lull at work right now, so this is the perfect time
> to do this- when there is no chance that it will interfere in any way
> with running "real" parts.
>
> For what it's worth, the fixation on stainless here is a result of a
> few different factors- first, I am fairly certain that the melting
> point of stainless steel is higher than that of carbon steel, though I
> have not looked it up. Second, my gas forge, fabricated from
> cold-rolled carbon steel, and painted with hi-temp barbeque paint has
> developed some surface rust after less than six months of use. And
> third, I just want to use it because it's cheap and easy for me to get
> (There has to be *some* compensation for living on the edge of
> outright poverty in a small job shop, after all...)
>
> The hood will likely just be made from whatever galvanized sheet we've
> got tucked away. It doesn't seem necessary to go all-out with the
> stainless for that, considering the price of the stuff these days.
Stainless turns to garbage under sustained high heat conditions in the
presence of oxygen. If the pot is well laid out and used, it should stay
fairly cool anyways.
I'd be none too thrilled about the chrome and nickel burning off into
the area either. I find that I taste the stuff when polishing, grinding,
or welding stainless.
My prefs would run towards mild steel plate, say 1/2", and a coat or
three of a high heat ceramic paint.
Rust and corrossion are just a reality. <shrug> You can accept that it
happens and get on with things, or you can do battle with it forever,
and it gets in the way of getting on with things. It still rusts, though.
I like the idea of stainless for the hood better than for the pot.
Lot's of stainless sheet goods ripped out of resaraunt installations and
commercial kitchens, that could be drafted into the duty.
If I had to PAY for the stuff.... Gavanised is good! :-)
Cheers
Trevor Jones
The forge pots I have seen were of cast iron. Cheap and durable
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