Backyard brass casting fun

[MushCreek]

I've been trying to cast a brass plaque for my rowboat. I say 'trying', because it's been mostly failure, although the last try (number 4) might be good enough. If nothing else, I'm running out of materials. I have a small old heat treating oven which supposedly goes up to about 2000 F., but the temp gauge doesn't work. I bought a small clay/graphite crucible which just barely fits. I cut up a bunch of old brass rod to melt. I made the mold out of wood and little plastic letters. The frame is also wood (bad idea). I screw the mold on, ram casting sand in there, then screw the back on. Carefully remove the mold, leaving the sand ready to cast. I earned the hard way that the mold is supposed to be hot (1100 F.), but I have no way of heating it that hot even if the wood frame did stand up to the heat (it won't). Wood supposedly combusts at about 500 F., so I preheated it as hot as I dared in a small toaster oven.

After 4 tries, this is about as good as I can get it. The heat treat oven has a broken element, which I patched by running a screw into it, and it tends to break each time I fire it up. I don't think the sand is quite hot enough, as the letters don't want to fill completely. As it is, it looks old-timey, like it was dredged up out of the ocean after 100 years, so it has the patina that I want (or am going to have to live with). The blank raised pad is going to have my name and the year I built the boat as soon as I can find someone to engrave it. I want deep engraving, not the wimpy little scratches that trophy shops do.

The mold is gray/black because I dusted it with powdered graphite to help it release from the sand.

 

[Shiftless]

In my opinion, that looks like a great finished product. If it was perfectly smooth, I don’t think it would match the vibe you are looking for.

 

[whateg01]

What material are you running out of? Are you not remelting the failed attempts?

 

[MushCreek]

I have brass, but I'm running out of casting sand, and I'd have to remake the mold frame- it's pretty burnt up now. I should have mentioned that safety is important when casting metals. I'm suited up head to toe, and a face mask. I'm doing it outside to avoid the zinc fumes from melting the brass.

 

[californiamilleghia]

Looks good to me ,

I wish I could find a backyard aluminum caster to make a few things ,

 

[bluedog225]

That looks pretty good. Particularly in light of all the limitations you described.

 

[Jayman17]

I agree with the others, that looks pretty good to me too. Just the right amount of rustic.

 

[dogdog]

maybe give these guys a call, saw them a lot on ebay selling casting equipment. Ask them which flux is for brass, aluminum or copper.

Casting Fluxes for Jewelry | Metal Refining & Casting Supplies

Shop casting fluxes for jewelry making. Prevent oxidation, remove impurities & improve casting quality for gold, silver & precious metals.

www.pmcsupplies.com

 

[Snip's]

I like the "vintage" look that you achieved... Nice work...

I have a few rental units and worked with a local "One man foundry" to make custom unit numbers...
He pretty much had a run down shack by the railroad tracks, with a "Glory Hole" in the dirt floor...
He did really superb work, but only worked from early morning to noon because of the heat...
He did everything from brass, aluminum and "German Silver"...

Here's one of the unit number plate he made for me...


Capital Brass & Aluminum Foundry

 

[tarmy]

Looks GREAT!

Nothing beats homemade…

Now, iffin’ that was cast outa spent shell casings (that you shot) that would be even better…(not sure that is even the same type of brass).

 

[The Cobbler]

to me that has a great rustic old rowboat look to it. I would be happy to use that in a heart beat

 

[RoninB4]

The rough, mottled background is a nice contrast to the smoother raised surfaces. The rough background breaks up reflective light and enhances, by contrast, the raised surfaces that you want seen. The address plate above is a good example of this. Things that look too perfect also suggest it's not made by you. I'd go with what you got.

 

[mv213]

I've been trying to cast a brass plaque for my rowboat. I say 'trying', because it's been mostly failure, although the last try (number 4) might be good enough. If nothing else, I'm running out of materials. I have a small old heat treating oven which supposedly goes up to about 2000 F., but the temp gauge doesn't work. I bought a small clay/graphite crucible which just barely fits. I cut up a bunch of old brass rod to melt. I made the mold out of wood and little plastic letters. The frame is also wood (bad idea). I screw the mold on, ram casting sand in there, then screw the back on. Carefully remove the mold, leaving the sand ready to cast. I earned the hard way that the mold is supposed to be hot (1100 F.), but I have no way of heating it that hot even if the wood frame did stand up to the heat (it won't). Wood supposedly combusts at about 500 F., so I preheated it as hot as I dared in a small toaster oven.

After 4 tries, this is about as good as I can get it. The heat treat oven has a broken element, which I patched by running a screw into it, and it tends to break each time I fire it up. I don't think the sand is quite hot enough, as the letters don't want to fill completely. As it is, it looks old-timey, like it was dredged up out of the ocean after 100 years, so it has the patina that I want (or am going to have to live with). The blank raised pad is going to have my name and the year I built the boat as soon as I can find someone to engrave it. I want deep engraving, not the wimpy little scratches that trophy shops do.

The mold is gray/black because I dusted it with powdered graphite to help it release from the sand.

If you want the raised areas smoother you could hold it on a belt sander with maybe 220 grit for a couple of seconds. If you have access to a wide enough sander to do the entire face at the same time it would be super easy. I agree with the others though, I like it as is.

 

[MushCreek]

The problem is that the letters didn't completely fill, so I'd have to just about grind everything away. I did mill the pad so it could be engraved. I'm gradually learning as I go. I think a lot of it is operator error at this point. I do like the rustic look, but the toolmaker in me is annoyed that I can't get it better.

 

[2oolhound]

Good on you for doing this! I thought wood was the defacto standard for the molds. What are the dimensions? I'd go with what you have there too.

You should think about doing the engraving too. Think of all the more tools you could get for it.

 

[MushCreek]

The wood would be fine, except the brass freezes too fast to fill in the details. As I did more research, I learned that the mold itself has to be pre-heated. My little toaster oven is good to 450 F., but the wood starts charring at that temperature. I made a steel frame today, and I'm going to pre-heat it in my gas grille, which goes to about 650 F. If I could get my hands on an old pantograph, I'd do my own engraving. Or... a CNC machine!

 

[whateg01]

How hot is the molten brass? It takes longer to chill and solidify if it's hotter.

 

[PCustoms]

How hot is the molten brass? It takes longer to chill and solidify if it's hotter.

Along with this, are different alloys better for casting?

Is there something you can add to yours?

 

[MushCreek]

I have no idea what temperature I'm hitting, but probably around 2000 F, the hottest the oven goes. 'Red' (copper based) alloys are expensive. I have lots of 360 brass to play with. I bought a pound of bronze, but it's expensive, and requires a hotter temperature than brass.

 

[mike93lx]

That looks great. Hit it with a wire wheel and do the engraving.

 

[OccupantRJ]

The problem is that the letters didn't completely fill, so I'd have to just about grind everything away. I did mill the pad so it could be engraved. I'm gradually learning as I go. I think a lot of it is operator error at this point. I do like the rustic look, but the toolmaker in me is annoyed that I can't get it better.

It is not that you can not get it better. It is so far, you have been unable to achieve your goal.

 

[OccupantRJ]

The wood would be fine, except the brass freezes too fast to fill in the details. As I did more research, I learned that the mold itself has to be pre-heated. My little toaster oven is good to 450 F., but the wood starts charring at that temperature. I made a steel frame today, and I'm going to pre-heat it in my gas grille, which goes to about 650 F. If I could get my hands on an old pantograph, I'd do my own engraving. Or... a CNC machine!

I was involved with wood branding tools. We had bronze letter bars professionally cast that had 8 letters per bar that were machined for insertion into a branding tool. I often saw inclusions in the letter faces of those bars also. The foundry would grind into the face of that particular letter to alert that it was a reject. There may be some sort of flux or additive that would make the material flow better into the mold. A different sprue or multiple vents may help trapped air escape ahead of the molten metal. By the way, that looks great for your application!

 

[john.k]

Brass should have more than 25% zinc to cast ...the rod may be coldworking brass ,as in cartridge cases .............these brasses do not have enough zinc...............I d think another 10%-20% of zinc will make the mould fill better.

 

[Threadkiller]

I think it looks great man, what do you use for casting sand? Is there a place that sells it or do you just make your own?

 

[gba2331]

That is awesome, I never thought about casting my own metal. This is exactly what I love about this site, it makes many things seem much more achievable.

 

[Firebrick43]

I was under the impression that any casting of any size is done in bronze due to flow and solidification properties? And that brass was limited to small jewelry pieces???

I would guarantee that the plaque in Snips post 9 is bronze.

 

[Shootinok]

I think it looks awesome.
Acknowledging the perfectionist in you, but I think if everything was clean and precise, it wouldn’t have the same authenticity.

 

[MushCreek]

It's an open top mold, so no need for any venting. I'm just pouring the metal onto the sand. It surprises me that the sand doesn't move, but I pack it pretty hard. I bought the casting sand through Amazon.

I hear you on the zinc. One of the problems is that the zinc tends to go away, particularly if you get it too hot or for too long. I know I can get a decent pour with what I have, as some of the letters came out perfect. It's just hard to control it between the heat and being suited up head to toe in protective gear. I knew a guy that was horribly disfigured pouring lead, which is nowhere near as hot as brass. That's an added safety feature of preheating the mold; it will drive out any moisture.

 

[whateg01]

Why aren't you reusing the sand?

 

[MushCreek]

I am, but the top layer gets badly burnt, and they said to discard the discolored sand. With preheating the mold, about half of the sand is ruined each time. It's not very expensive; I just didn't think I'd ever use more than 5 lbs. of the stuff. I'm getting hooked, though, so I may venture into casting aluminum, which is a much lower temperature. Easier to find scrap aluminum, too.

 

[whateg01]

I dunno how much you spent on the sand but "real" casting sand can be reused

 

[MushCreek]

Not the burnt part. I think it can be rejuvenated somehow, but it's not worth the bother. It has some kind of oil in it or something so it packs together. The burnt stuff won't pack.

 

[Firebrick43]

I dunno how much you spent on the sand but "real" casting sand can be reused

There is green sand, which absolutely can be ran through a sand muller and reused.

However MushCreek is using petrobond which typically gives better surface finish than green sand. As it name infers, it uses a petroleum based binder vs bentonite clay like green sand uses.

He is correct that the sand adjacent to the metal is burnt is sifted out and is tossed. The bulk of the sand that is not burnt can be reused.

 

[MushCreek]

Yes, the sand actually catches on fire when the hot metal hits it. That's the binder burning off. That's part of what makes it tricky to get a good pour. There's smoke, fire, zinc fumes, and I'm covered from head to toe. You're handling the tongs with heavy welding gloves, so precision isn't really all that good. I wonder if it would actually be better if I made a two part mold with a gate and sprue on one end, and just poured the brass in. The only aiming would be getting the brass into the hole. I'd have to change the mold around, and incorporate a vent as well.

 

[PCustoms]

Yes, the sand actually catches on fire when the hot metal hits it. That's the binder burning off. That's part of what makes it tricky to get a good pour. There's smoke, fire, zinc fumes, and I'm covered from head to toe. You're handling the tongs with heavy welding gloves, so precision isn't really all that good. I wonder if it would actually be better if I made a two part mold with a gate and sprue on one end, and just poured the brass in. The only aiming would be getting the brass into the hole. I'd have to change the mold around, and incorporate a vent as well.

What if you change the sand to the other material?

 

[MushCreek]

Well, I'd have to find a source. As Firebrick43 said, the petrobond gives a much better finish. I have enough sand left for one more shot. After that, I may source some green sand and see how that works.

 

[PCustoms]

Well, I'd have to find a source. As Firebrick43 said, the petrobond gives a much better finish. I have enough sand left for one more shot. After that, I may source some green sand and see how that works.

Well, right down what's gone well and what hasn't. Look it over and map out your plan for the final attempt.

 

[Firebrick43]

Green sand is very easy to make yourself. I actually don't know if you can even buy it?

Its nothing more than a fine screened sand with bentonite clay and water added although it takes a day or two for the clay to properly absorb the water. The bentonite clay is available from any well driller or water supply store as its used for drilling wells.

To me there isn't anything wrong with the mold or at least the impression in the mold or its sand. I would guess its a metallurgy problem/fluxing issue, incorrect pour temp, or a sprue/runner issue but there are no pictures to see the other half of the flask with those cut in.

 

[PCustoms]

To me there isn't anything wrong with the mold or at least the impression in the mold or its sand. I would guess its a metallurgy problem/fluxing issue, incorrect pour temp, or a sprue/runner issue but there are no pictures to see the other half of the flask with those cut in.

I don't think there is another half...

To me it's the brass vs. bronze issue

 

[Firebrick43]

I don't think there is another half...

To me it's the brass vs. bronze issue

I missed the fact it was open poured without the other half.

I very much think that could be an issue, I have never tried that before and even where the sprue is there is a lot of shrinkage where the metal is exposed to the air.

But I do agree, I have never seen brass poured for an intricate casting, only bronze. The only brass I have seen poured was oversized an machined for plain bearings.