Ultimate Guide to Making a Cheap but Effective Aluminium Forge.

Step 5 Now What?

We now have a lot of ingots. You now can use the rest of your free time planning on how to get a hold of a harbor freight micro-mini-lathe for $250.

I figure we could cast some blanks that can be worked in a tiny lathe but that's for later.

We'll Make an instructible on casting aluminum when we get it down to a simple science.

We hope you enjoyed this instructible and happy smelting.

Comments

[Data643]

You could spend all of your time saving up for a lathe. Or... you could just cast your own using David Gingery's Books. I have his metal lathe book & it's awesome.

[r_harris2]

I know this is long time later to reply, but I thought I would post the counter-point to this. I think the Gingery lathe is a good project in itself, if that's what you want to do, but if you want a lathe, probably quicker to buy it. Think about it, a decent 7x12 lathe plus some tools is about $400. That's only six weeks of working part-time at a minimum wage second job. Not as enjoyable perhaps, but much faster than starting from scratch, casting metal and hand scraping the ways on the lathe, etc.

I considered the build-my-own approach, but I wanted to make some stuff, besides the lathe itself, and I am glad I bought the lathe. Once I had the lathe, I did a lot of little things that were really fun and easy. I doubt I would have finished the Gingery lathe. It is a pretty big project in itself, and I notice that you can find lots of web pages showing the start of a Gingery lathe, but last time I looked, I could not find ANY of a finished Gingery lathe and something made with it.

[Data643]

I do see your point in that it would take less time and require less work, but a Gingery Lathe would cost far less. Where have you seen any 7 x 12 metal lathes for under $400? The cheapest I can find them for is about $550 for a 7 x 10. Here is a link to a near - completed Gingery lathe machining its own tailstock ram.

[r_harris2]

Yikes! I am in shock. I didn't realize they had gone up so much since I bought mine. I am becoming one of those old guys who say "Back in my day sonny, you could buy..."

But I will STILL stand by the basic idea. Only go in for a Gingery Lathe project if you really want to build the lathe. If you want to turn metal, a few months of part-time work, say $750, will get you a better lathe, with a 3 jaw and a 4 jaw chuck and a selection of cutters, boring bars, a dial indicator set and a few other starter items.

Oh yeah, with a little effort and talking to your favorite garage saler / flea market fanatic and you might get a call on a saturday morning...

[lostowl05661]

I just used my forge for the first time and it worked GREAT!!! I couldn't find the right torch that the author had used, so I got a benzomatic grass burner and bent the shaft to fit. See below. I have a question, though. There seemed to constantly be a skin of aluminum on the top during the melt. Is this normal surface tension or was it not hot enough?

[remik7]

This might be slag (impurities (paint, non metal material) from what you are melting, if you are melting pop cans, this is sure to happen. don't worry though, you can simply take it off using a small metal "rake", to skim it off. Hope this answered you question.

[lostowl05661]

Also, what is a good space between the crucible and the refractory? Mine seemed like a lot of space, I may pack it in a little with fireclay.

[lostowl05661]

How hot a torch? I found that if the blue flame from the propane torch wasn't directly on the crucible, it wasn't hot enough, even with a forge lid. When I made the handle the crucible, it suspended the crucible about an inch above the inlet for the torch. Even after 15 minutes the crucible didn't heat to red hot. I put the crucible down on the base refractory and it heated right up. Also, I was able to put the can lid back on to keep some of the heat in. I think I'll have to do it that way and pour with channel lock plier. It must be that even the grass burner torch doesn't produce enough heat. Still, doing this project really helped me feel like I could do this. Next weekend's project: The Gingery Charcoal Forge!!!

[didgitalpunk]

you could use an oxygen-acetylen torch but don't. why? simple: it can make holes in 5mm tmpered steel sheets. OC2H2 torch VS crucible, well say bye to your crucible.

[hintss]

will a bunsen burner work?

also, ceramic and graphite crucibles

[John Smith]

That "skin" is dross, or slag. It's a layer of floating oxides and impurities on top of the real metal. You should skim it off after adding metal and before pouring. From my experience, I'd go right to propane, skipping charcoal. It's more expensive to begin with, but it's more rewarding in the end.

[lostowl05661]

Well, I'd need a better burner. i've seen some sites on the web to explain how to make a good propane burner. The bean can has been a problem, and I am out of propane bottle crucibles. The steel crucible I had doesn't get hot enough with the propane torch I have (which has now deteriorated beyond the point of safe use) So, anyway, I have my charcoal forge now, and I'll use that until I can make a decent burner for it, then I'll convert it to gas.

[John Smith]

Well, if you do make one, I can tell you what burner i made. It works great, very VERY sturdy. Charcoal is great, but I have to say, the second you use a good propane burner, you'll think you were dumb to even try charcoal. No comparison. BTW, I really think that this instructable needs to be renamed. ITS NOT A FORGE! Forges are used to shape metal, this would be considered a furnace. The whole setup; a foundry. Of course it could be used for minor forging (maybe, i probably doesnt get hot enough), but the name is Al Forge. So either way, its a furnace. The name should be "Ultimate Guide to Making a Cheap but Effective Aluminum Furnace" I disagree with 'ultimate', because it misses out on critical, key points of casting aluminum, and other non-ferrous metals. IM me, (AIM), at Alt Ctrller. Or Email at [e-mail]. Or comment back here. hope that helped

[John Smith]

oh, and like i said, if you want to have nothing but fun, very little work, propanes good too. No setup, no maintenece.

[A good name]

It would be soooooooooooo awesome to sell the ingots for money... you could start your own aluminium recycling center :D

[teeth10]

that would be pretty useful, aluminum ingots cost around $20.00 a pound, and just think about how much aluminum a average city recycles? just put up some trashcans with "aluminum recycling" on top throughout the city and you could make a lot of money (especially in calif. or some really green place!) This is about 215 pounds worth of aluminum ingots in the pic

[kwxj61b]

Have you sold it for $20/ lbs? Because I really like to know if it's true or is it an urban legend, due to the fact that LONDON Metal Market price for Aluminum is around $1.02 / lbs USD.

[kingcr3b]

a few words, FUN FUN FUN! But with the ingots can you re melt them so you can make valve covers, engine blocks, heads etc. as long as you have the sand castings. because I want to build a F1 engine... maybe... I drink a lot of canned drinks and i steal some out of everyones waste management recycle bins. oh or can i just make little parts out of aluminum?

[Steve66oh]

@Kingcr3b - It's a big step from here to casting engine parts - right off the bat the issue is metallurgy - what alloy is used in pop cans? Then, to cast a cylinder head or block in one pour (no other way), you'll need to build a much bigger system. For a job that size, you'll want to melt & cast under vacuum or argon atmosphere - oxygen (air) is dangerous around molten aluminum, that's why aluminum is ALWAYS welded with a shield gas. Finally, even the pros have trouble sometimes casting large aluminum pieces - granularity, brittleness, porosity... lots of problems if the process isn't very tightly controlled.

@All - a couple years ago, I took 600 cans to the recycling center, I got $6 for 'em. A penny apiece. Of course, the center has to make money, I'd bet they got $.02/ea for 'em... and the foundry probably gets $.04/ea after melting them into ingots... at most, I believe my 600 cans might have represented $24 worth of aluminum.

Part of the problem is that the cans are so thin. All aluminum forms a layer of alumina (aluminum oxide, clay) on the surface. Take a can, hang it from a hot dog stick, near the glowing coals of a hot campfire. The aluminum will melt & flow, forming a bulge at the bottom of the can. The oxide coating will not melt. By this, you can see how much of the can's mass is oxide. If your goal is to cast aluminum parts, you're much better off to buy/melt solid shapes of specific alloys - with bar stock, a MUCH smaller percentage of mass is oxide.

[2 stroke]

realy we get 5 cents a peice

[hodwooker]

You need to look into a few books on metal casting. The best source I know of is Lindsay publications www.lindsaybks.com/ the best books they have for the beginner are by Dave Gingery. He has a great book on a charcoal foundry that leads into building a complete home machine shop. Also there are many other books on foundry skills and practices.

[K.hall86]

shark, this is a pretty sweet setup! I have a little bit of experience with melting aluminum and brass in a oxygen blown concrete forge. one thing that i see could help out would be to make a concrete lid. all the forges that i have used, incorporate a two to three inch thick donut shaped lid that can be lifted and swung away from the combustion chamber. with an insulating lid you will be able to reach melting temp much faster, and also provide a safety feature. I think that if you produced a forge that used two torches, (one on the opposite side of the can) it would provide even heating and potentially higher temperatures. Also, in my reading, i am mot sure if i read correctly, but it appeared that you said to preheat the crucible, and then add the metal....this is, in my opinion, a bad idea. although it is not commonly heard of, Aluminum can create air pockets that will in essence pop like bacon grease in a hot skillet...all metal that is to be melted should be placed in the crucible, inside the forge before lighting. i only say this in caution....i have seen a raindrop sized spec of molten Al burn through a denim shirt and half an inch into a co-worker's back...1400 deg. F is no laughing matter. aside from that, i do indeed like your design! and hope to see more from you. P.S. when you get into the casting phase, be sure to preheat molds as well...hot molds allow for greater details.

[Shark500]

Thanks. it's good to hear from people with experience. That's pretty much what instructables is about. The only reason i preheat is because I'm afraid the aluminum will sink away all the heat especially with large pieces. I didn't know of the potential hazard so thank you for the tip. My cousin also suggested the twin blower design but they are quite pricey. He also suggested a lid but the handle I put on the crucible gets in the way. If I had a welder I could make a better design but this is pretty much a minimalist (cheap) guide. lol I'll look into other possibilities to better facilitate a lid. I really appreciate our input. Thanks for the comment

[NewB007]

I agree with K.hall86 about the preheating. If you want to add more aluminum after you already have a melt, though, you can place the new material near the heat and pre-heat the aluminum to drive out any moisture before adding it to the crucible. Give it several minutes, and add it slowly.

[aqwiz]

there's an instructable for an arc welder from three old microwaves you know :p

[butthead95]

yeah just make 2 indents in the lid for the hndles

[srilyk]

Use your cardboard method to create "bumps" to put over top of the handles - that will get you the best of both worlds.

You're right about wanting to eliminate moisture -- even one small drop (even, say trapped soda), if it's below the melting aluminum, will most likely create a large explosion firing molten aluminum, slag, and most likely bits of forge everywhere.

I've heard of carts being blown to pieces and wheels thrown through/into metal walls. So be careful!

I'm not sure how your speed quench will affect the strength (or weakness) of the aluminum - often times too fast will create metal that's brittle -- weakened by the thermal shock. And then there's the possibility for slight explosions - you're right about it being dangerous, but it can also negatively affect the metal - I'd do some research on the topic before continuing with my impatience ;)

Great Instructable though!

[fgleich]

From what I've read, letting the metal cool normally makes it really hard ( Aluminum of course ), and quenching it suddenly like that softens it. This is the opposite of steel

[Shark500]

meh, it's going to be melted down again anyway. We use full face shields and do cover the crucible so i assume the damage would be minimal. we haven't had a blowout yet but... meh. que serra serra. thanks for the comment

[solidification]

"Smelting" is a little different from what you are doing. Take the "S" off and you've got it. (Smelting is more related to reducing the element from its mineral compounds.) Some words of advice: you can preheat the metal or just stick it into your "crucible", its all the same. (although you might as well just put it into the "crucible" so it retains the heat a little better rather than acting like a heat sink) dont worry about the Al sucking away heat while its in the crucible. It all needs the same amount of energy to melt. When I charge a melt in the #30 I use, I place a very small amount of Aluminum(356) into the base of the crucible so its not touching the sides at all. I allow this to become liquid after about 10-15 min and add the rest of the charge so long as it does not touch both walls at the same time. The advantage to letting a small amount become liquid before adding more metal, is the liquid has greater surface contact with the new metal. The liquid Al has much better thermal conductivity than the hot gasses in the crucible, such that it aids in heating the rest of the added charge. As for adding more metal.. do not drop/plop metal into the crucible. use some longer tongs to feed it in. This will avoid spatter. Also, the reason for not allowing pieces to touch the walls of the crucible is due to the thermal expansion of the metal. In a ceramic crucible, the added stress on the walls leads to deterioration of the walls with cracking and eventually failure. (a steel cup might not have as much of an issue with that). As for the crucible you have, you might not realize it, but you are transferring iron from the can into the liquid Al. It might seems strange because its not hot enough to melt steel, but diffusion happens even at room temperature(just... really really really slowly). At warmer temps like 660C, iron can diffuse quite a bit more rapidly. for future considerations, you might want to stay away from galvanized steels*. Placing them into the furnace is bad for two reasons: 1. Safety. Zinc Oxide is pretty bad for you. 2. Zinc diffuses very quickly into the steel (faster than you can burn it off if you tried). there is a degree of LME which takes place, but its more about the brittle intermetallics that form and are prone to failure. *you can easily remove the zinc with warm/hot lemon juice or vinegar if you can stomach the smell. A propane setup is your best bet for DIY home stuff. it is pretty cheap still and create heat quickly. Propane + small blower will get you nicely into the superheating range for bronze. a welding unit (oxy/acet, stick) is a great investment for someone who wants to create and explore science and make stuff. MIG/TIG are nice things too, but perhaps not worth the investment for you just yet. (it is difficult to justify $500 or $1500 on something you might not use very often) (and oxy/acet and stick offer a wide variety of applications... even joining aluminum or bronze castings...) You could save up and drop money into a manufactured furnace and probably save some $$ in the long run... BUT... nothing beats those evenings of running your own backyard furnace (the fifth or sixth version of that furnace probably), roasting some marshmallows and sitting back listening to that baby roar as the sun sets. Keep it up.

[Shark500]

Wow thanks for the info.. How does the iron in the aluminum affect it? How much does a professional furnace cost (about)? This is a lot of useful information. I've just started my journey into the world of metal smithing so this very valuable to me. This is one of the best things about instructables. That people can share ideas and learn from more experienced people. Thanks for the info.

[solidification]

The iron going INTO the Al is actually not that bad at all. Iron only has a 0.05% solid solubility in the Al near 660C. The rejected iron Al3Fe precipitates actually end up working as a strengthening mechanism. (this retards dislocation motion in the crystal, inhibiting plastic flow which overall, increases yield stress)

If you were to slice one of your ingots and polish the edge (really really polish it down to at least 600 grit sand paper and either polish it with some diamond slurry or etch it with a hydroxide or HF(can be purchased in solutions for stained glass hobbies), Then examine it in a microscope, you would definitely see those iron precipitates as little black specks scattered around the sample.

For casting ingots or small DIY simple castings, there is not an issue with the alloy. Pot metal works for just about anything you want. (although the shrinkage is horrific and fluidity sucks without a great deal of superheat)

The downside to this is that you are slowly eating your crucible. So try to get as much of the post-pour metal out to inspect the crucible for pitting. This will be a rough surface that looks eaten away. Some time down the road, this might create a leak in your steel crucible (or worse).

Ranking furnaces from 1-10, 1 being coffee-can DIY, 3 being hobby, 5 being small scale production... 1-2 is pretty cheap (as you know). 3-4 is going to be anywhere from a well designed DIY setup costing ~$200 to $1000.
All said and done, the furnace I use most often now cost around $5000. not to mention having a 2 inch natgas line installed to run the thing. This is a Mifco furnace. you can check out other mifco products from http://www.mifco.com.
This unit can melt a lot. It can supposedly melt white cast iron (this is one of the lower melting point cast irons), but I have not really tried it yet.

one last thing:

assuming you cant weld... You can still create your own tools by using the exhaust gasses from your furnace to heat up steel to a plastic working temperature. You dont need an anvil or anything. just a pair of hammers. Secure 1 large (like 4 lb) masonry hammer (that is not precious to you) to a table or tree stump and this is effectively an anvil. Be sure to strike the face of the hammer, not the sides. You can now heat up scrap steel rods, and pull them off the top to hammer. This is how you can create some better tongs and crucible yokes.

Harbor Fright carries some good stuff (by good i mean, it didnt pass inspection to be sold as a brand name, but while full of defects, still useful and very affordable. Stay away from the vises and anvils from there though. They tend to use grey cast iron bodies with a capped high carbon steel face. This stuff probably already has cracks in it. it wont hold up to long use.

[Shark500]

Thanks. so the iron isn't too bad. I have a nice wire brush that I use to clear out any scale on the sides of my crucibles in between firings. Do you have any ideas for a non expensive but longer lasting crucible? I have a few ideas to make a better diy setup but for now, this works for me. I've played with trying to weld street sweeper bristles like you said (my vice has a striking surface ( it's a harbor freight vice) but it works so far.) It started to meld together a little but i doubt my torch (without added oxygen) can produce much more heat. I plan on making some tools out of aluminum to accommodate my other hobbies (like locksmithing). I can make some plug followers etc because I just need something solid. I know my thirst for molten metal will lead me much further.

[Bro. Jones]

Use a brick for a lid. When learning ceramics we used bricks to cover peep holes in the kiln. Just be sure the smoke can escape or you will smother the flames.

[Shark500]

I was always told not to use bricks because they could explode. firebrick would be nice but no one sells it around here. Thanks for the comment

[TMonkey]

How do you preheat the molds? Use the torch? Bake 'em?

[SeverinR]

This link shows the dangers of copper. "Inhalation of copper fumes may give rise to metal fume fever" With the gas from the Galvy can, I think if you do this in a well ventilated area, you should be safe. If someone has copper wire, try melting it. BTW if you have Urainium, its melting point 1180 degrees. Don't try it, I was just kidding. Found that while looking for copper melting warnings.

[geodez]

IGNOT FIGHT!!!

[ArtificialPulse]

This was really an amazing project. Thank you so much for putting this instructable together! I can't wait to build my own!!

[hailtothkngbby]

Great work! Nicely documented! Now I have to clean out a new "smelting space" in my garage and it's all your fault. When my girlfriend complains, I'm sending her directly to this instructable.