Foundry From Scrapped Oven for Cheap, Clean Castings

Home-built foundries are a popular project, and with good reason. Being able to melt and cast metal is a powerful tool, even if it’s “only” aluminum. But the standard fossil-fuel fired foundries that most people build are not without their problems, which is where this quick and clean single-use foundry comes into play.

The typical home foundry for aluminum is basically a refractory container of some kind that can take the heat of a forced-air charcoal or coal fire. But as [Turbo Conquering Mega Eagle] points out, such fuels can lead to carbon contamination of the molten aluminum and imperfections when the metal is cast. With a junked electric range, [Turbo Conquering Mega Eagle] fabricates a foundry that avoids the issue in an incredibly dangerous way. The oven’s heating element is wrapped around an old stainless saucepan, fiberglass bats from the stove insulate the ad hoc crucible, and the range’s power cord is attached directly to the heating element. The video below shows that it does indeed melt aluminum, which is used to sand cast a fairly intricate part.

We can’t see getting more than one use out of this setup, though, so it’s only as sustainable as the number of ranges you can round up. But it’s worth keeping in mind for one-off jobs. For a more permanent installation, check out this portable propane-powered foundry. And to see what you can make with one, check out this engine breather cast from beer cans.

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Brazing Aluminum

Where do you stand on one of the eternal questions of metalwork: brazing, or welding? As your Hackaday writer, and the daughter of a blacksmith, it’s very much on the welding side here. Brazed joints can come apart too easily, which is why in the territory this is being written in at least, they are not permitted for the yearly vehicle roadworthiness test. If you’ve ever had to remove a brazed-on patch with an angle grinder, you’ll know which one you’d trust in a crisis.

What if the metal in question is aluminum? [George Graves] sends us a link to a forum discussion on the subject from a few years ago, and to a YouTube video which we’ve embedded below the break. Miracle brazing rods claim astounding toughness, but the world divides into those who favour TIG’s strength versus those who point to brazing’s penetration far between the surfaces of the metal to be joined. Having experimented with them a while back, we’ll admit that it’s true that aluminum brazing rods join broken parts impressively well. But yet again you won’t see this Hackaday writer riding a bike that wasn’t welded with the trusty TIG torch.

Take a look at the video, and see what you think. Even if it’s not a joint you’d stake your life on it’s still a technique that’s a useful addition to your workshop arsenal.

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Portable Lightweight Foundry

[Makercise] is getting ready for Maker Faire. One of the things he’d really like to do is some casting demonstrations. However, he has no desire to take his expensive and heavy electric kiln based foundry to Maker Faire. So, he made his own.

He got into metal casting during his excellent work on his Gingery lathe series. He started off by modeling his plan in Fusion 360. He’d use a 16qt cook pot turned upside down as the body for his foundry. The top would be lined with ceramic fiber insulation and the lid made out of foundry cement. He uses a Reil style burner, which he also modeled as an exercise. This design is light and even better, allows him to lift the top of foundry off, leaving the crucible completely exposed for easy removal.

All went well with the first iteration. He moved the handles from the top to the bottom of the pot and filled it with insulation. He built legs for the lid and made a nice refractory cement bowl on the bottom. However, when he fired it up the bowl completely cracked along with his crucible. The bowl from design flaw, the crucible from age.

A bit put off, but determined to continue, he moved forward in a different direction. The ceramic insulation was doing so well for the top of the foundry that he decided to get rid of the cement altogether and line the bottom with it as well. The lid, however, would be pretty bad for this, so he purchased another pot and cut the top portion of it off, giving him a steel bowl that matched the top.

The foundry fires up and has worked well through multiple pours. He made some interesting objects to hopefully sell at Makerfaire and to test the demonstrations he has planned. The final foundry weighs in at a mere 15lbs not including the fuel cylinder, which is pretty dang light. Video after the break.

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Copper Thermite Explodes and Smolders Successfully

It was quite a surprise to learn that thermite isn’t just rust and aluminum powder, but describes any combination of metal powder, metal oxide, and optionally fuel mixed together in a reactive ratio.  [sciencewithscreens] shows us some of the properties of a copper (II) oxide based thermite.

We can only assume he has a thing for copper as an element. After growing his copper crystal it wasn’t long before he followed a winding road of copper based experiments and found himself with a supply of copper (II) oxide after rendering it from common household chemicals. He had two missions for it. The first was to witness an unfettered copper oxide based thermite reaction. Some had assured him it was practically explosive. The other was to attempt refining pure copper using the reaction. That would be pretty cool considering it all started out as an impure blend of laundry detergents and fertilizer.

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Garage-built Aluminum Miniboat Tears up the Surf. Or Not.

It’s the water-borne equivalent of building a minibike out of steel pipe and an old lawnmower engine. Except it’s a DIY personal watercraft made out of aluminum and an old chainsaw, and it has that same garage build feel – and the same disappointing results.

When we first saw the video below, we were hoping for one of those boats that let you water ski by yourself, or a wave-hopping, rooster tailing DIY jet ski. Alas, the chainsaw [MakeItExtreme] chose to power this boat is woefully underpowered, and the boat barely has enough oomph to make a wake. [MakeItExtreme] acknowledges the underwhelming results and mentions plans to fix the boat with a more powerful engine and a water jet drive rather than the trolling motor propeller they used. Still, whatever improvements they make will probably leverage the work they put into the hull, which is a pretty impressive display of metalwork. We’re used to seeing [MakeItExtreme] work in steel, so it was interesting to watch aluminum panels being cut, bent, and welded into a watertight hull. Looks like there’s plenty of room in there for more power, and we’re looking forward to version 2.0 of this build.

If you like rough and ready metalworking videos, there are plenty of them on [MakeItExtreme]’s YouTube channel. We’ve covered quite a few before, including this all-terrain hoverboard and a spot welder that’s more-or-less safe to use.

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Metal Casting With Single Shelled PLA Masters

[3DTOPO] does a lot of metal casting (video link, embedded below). That’s obvious by the full and appropriate set of safety gear, a rarity on YouTube.

They had all the equipment to do it the normal way: craft or CNC out a master, produce a drag and a copy, make any necessary cores, and finally; pour the mold. This is a long and tedious process. It has a high rate of error, and there is a parting line.

Another set of methods are the lost ones. With these methods the master is produced out of a material like foam or wax. The master is surrounded by refractory and then melted, burned, or baked out of the mold. Finally the metal is poured in. Theoretically, a perfect reproduction is made without ever having to open the mold.
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Learn Resin Casting Techniques: Cold Casting

Sometimes we need the look, feel, and weight of a metal part in a project, but not the metal itself. Maybe you’re going for that retro look. Maybe you’re restoring an old radio and you have one brass piece but not another. It’s possible to get a very metal like part without all of the expense and heat required in casting or the long hours in the metal fabrication shop.

Before investing in the materials for cold casting, it’s best to have practical expectations. A cold cast part will not take a high polish very well, but for brushed and satin it can be nearly indistinguishable from a cast part. The cold cast part will have a metal weight to it, but it clinks like ceramic. It will feel cool and transfers heat fairly well, but I don’t have numbers for you. Parts made with brass, copper, and iron dust will patina accordingly. If you want them to hold a bright shine they will need to be treated with shellac or an equivalent coating afterward; luckily the thermoset resins are usually pretty inert so any coating used on metal for the same purpose will do.

It is best to think of the material as behaving more or less like a glass filled nylon such as the kind used for the casing of a power tool. It will be stiff. It will flex a relatively short distance before crazing and then cracking at the stress points. It will be significantly stronger than a 3D printed part, weaker than a pure resin part, and depending on the metal; weaker than the metal it is meant to imitate.

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