For some dang reason, at 72 years of age and 40 years of woodworking, I seemed to think it was a great idea to start yet another diy hobby…blacksmithing/bladesmithing. I have plenty of Ibuprofen, so why not? Anyway…this segues into leatherworking, because knives need sheaths. I also cast lead bullets for reloading ammunition (another hobby). Now, for my grandson’s birthday, I decided to make him a 5o% size replica of “Sting”…Bilbo Baggins’ sword. Everything was going great until the pommel, so now, I need another hobby…metal casting. Which brings me here with you fine folk. Many years ago, I was a Navy Dental Prosthetic Technician. I made crowns, bridges, full and partial dentures, etc., so I do have a good working knowledge of metal casting. I actually at this point have no intention of jumping into the deep end of the metal casting pool…just need a bit of help now and then. I have a gas forge, a bunch of sand, plaster of Paris, paraffin, beeswax, and candle wax. Back to the pommel. I am having a problem getting an aluminum casting done. As you can see in the photos, the pommel will set like a cap over the end of the wood handle (it will be drilled and tapped as a blind hole to screw onto a bolt welded to the end of the tang). I think the only way of making it is by lost wax casting…a sand casting won’t work because of the cup shape of the wax form. After waxup, I attached the form to a metal sprue, slurry-coated the form, then after it hardened, inserted into my invest. The prue is removed after that sets up. Three attempts have been unsuccessful….despite preheating the mold and melting the aluminum, the metal won’t get down into the mold. I need some secondary and vent sprues I’m sure, but this is all limited to needing to fit in the size of a soup can so it fits in my forge. Thanks in advance for any suggestions! Alan
Hello 6Sally5, Have you considered trying this in lost foam? That might be a way to solve a venting issue and get away from the soup can size constraint.
Welcome, Lost foam was my first thought even without seeing the pics. For one-offs...you can't beat it. The guard could be done in foam too.
I thought about the foam idea, but it’s critical there be a precise fit around the end of the wood handle. I’m not sure I could get that with foam, but then, I’ve never tried foam before, either. The guard is already done in steel. Another issue I have is the molten aluminum is kind of…fat, so rather than pouring out in a controllable stream, it plops out. I have a cheap Amazon graphite crucible which doesn’t have a spout formed on an edge. What do you think about my grinding a pour spout? Would it help?
I think the 'plop' is the clue that your metal is too cold and is freezing before filling the mold. Are you running a small crucible in a blacksmiths' type forge or is it a small foundry-type setup? Is the handle conical or cylindrical? I am guessing it would need to be to allow a blind threaded fit. If so, perhaps a hole in the foam can be made by wrapping a wood plug with sandpaper.
I have a two-burner bs gas forge. I have wondered if the metal wasn’t hot enough. It acts like the surface tension is too tough. I do drag the slag off as the aluminum melts, so I think it’s not a buildup of impurities. The handle is conical. In the photo, the handle is wrapped with foil to facilitate the wax buildup. Ah….I see where you’re going with forming the foam. So what is the advantage of foam over wax? As I said, I’ve never used foam for casting. With foam, do you not need to do a burnout cycle?
Lost foam is handled similar to lost wax except there's no need to burn out the foam like you'd do with wax, as it burns away with the hot metal. There's plenty of videos on youtube including one's from forum member Al2O3?:
With lost foam there is also no investment to cast and preheat. The coated and sprue'd pattern is packed in plain sand and made ready to pour. The lost foam section of the forum here contains good information. Start with the 'confessions' thread by Kelly (Al2O3). Here is a video of how to do lost foam work without a CNC, I can vouch for the part as it is in my possession : My guess is that you are fighting with the less efficient airflow in a forge versus a foundry furnace. By rights you should have enough heat, but the forge's burner orientation (typically pointing down and exhausting out both ends) and lack of 'swirl' in this configuration are conspiring against you when trying to use it with a crucible. I have a small single burner Amazon foundry special that does great with aluminum but is not capable of bronze.
Welp….after watching these two videos, which sadly don’t show the casting process, I’m going to give it a try. Frankly, I’m pretty tired of remaking the wax form, although after three times, I’m getting faster and better at it. Is this foam anything more than the pink foam panels you can buy at Home Depot?
It's XPS extruded polystyrene instead of expanded polystyrene beads although both can be used. Yes it's the pink foam panels, although in Australia where I'm located it's also blue and pale yellow.
Thanks Mark. I’m excited to try this. Does it truly require special sand or will standard play sand work just as well?
Thanks Tops and Mark. I didn’t mean to hijack this introduction section and was thinking I should move to a specialized topic. Sure appreciate the info from all!
Plain, dry, clean sand. I'd use some mosquito screen to get out the bigger rocks if using less expensive bags of sand. I have also bought paint texturing sand and mortar mix sand that don't need sifting.
Dig into that youtube page a little deeper, there a wealth of good information there, including videos that show the casting process. And the foam Kelly uses is just the stuff Homedepot sells.
Do you know how to subscribe and view videos on a (my) YT channel? There are plenty of my videos that explain the various process steps, materials, self made equipment, etc. You just have to be willing to view more than one video to learn about it. Thinking you can watch a single 20-something minute video and learn everything there is to know about lost foam casting sounds more like a Gen-Z'er than a 72 year old. If I included every step of every process on every video, they'd all be 2 1/2hrs+ long and nobody would watch them. On the other hand, if I can expend all that effort to make all the videos on my channel explaining those processes, is it too much to expect those interested to watch them instead of watching one and asking me to repeat how the rest is done? Sorry, don't mean to be overly harsh and wire brush you about it,........... just keeping it real. You could also take in the "Confessions Thread" that was suggested by Tops in his post above. It's a sticky and the very first thread in the Lost Foam sub-forum. Confessions of a Lost Foam Caster, 5 Years on. | The Home Foundry Best, Kelly
Yessir, I do and just subbed to your YT channel. I also have been reading Tops’ “Confessions” sticky….very interesting. Thanks again, Alan
I'll second the sifting of play sand, there's some serious chunks of gravel hidden in there. My next batch will probably be "fine sand" from the local Farm & Fleet. Also for something small like this, don't worry as much about packing the sand in. I did some golf ball size castings in a soup can with just hand ram, and they came out fine, though I used several rounds of wallboard mud.
Yes for small simple shapes you can often get away with a lot, but that changes very quickly as parts become larger, shapes more complex, or casting higher density metals. Then mold packing becomes very important. There is a tendency to want to think of the coating as a structural element of the mold, but it really isn't. That is the compacted sand. The coating improves surface finish and controls the rate at which decomposed polystyrene escapes into the mold. Thicker coating can be counterproductive, as it is less permeable. Though drywall "mud" is practical and effective refractory coating for hobby non-ferrous LF casting work, it's not all created equal. I recommend the non-setting light weight joint compound, because the additives that make it apply smoothly, and avoid cracking are similar to the those in professional refractory compounds and also make it more permeable, as does applying a thin layer. Best, Kelly
