Mold Issues

[rodwha]

So I decided to cast a few RB's yesterday evening. I began having trouble getting my mold to heat up well enough so I did as I've often read, which is to dip the mold into the molten lead. What happened though was lead stuck to the aluminum.

And one of the chambers has some sort of dark film that imprints on the cast balls.

Eventually I noticed that the mold would no longer close tightly and left a raised ring on the balls.

I've also noticed how beaten up the top of it looks, as well as one of the holes looks like someone took a screwdriver to it or something. This is only the second time I've used.

93606

93607

93608

As you can see there is lead stuck all over it, and I'm not sure if that's lead inside the cavities or not, but why wouldn't it have melted when molten lead was poured in?

[cali4088]

always heat your mold by "pouring" lead on the "outside" of it. i dont know about casting ammo, but to heat up my downrigger molds, I pour very hot lead on the outside of it several times to heat it up. This allows molten lead to stay molten longer so i can finish my pour. Also remember to lube your molds so that they open and close with ease. There is a possibility you have lead stick where the joint turns which is keeping it from closing all the way. What do you mean by a raised ring? Are you saying its not filling the mold properly? Are you casting with pure lead or lead with a lack of sufficient tin? Maybe your lead isnt as hot as you need it to get

[cali4088]

p.S. Are you fluxing properly? A lack of sufficient flux will leave your molds pocketed and ugly looking

[rodwha]

I had dipped the corner to heat it up as it worked well last time. But the mold wasn't filling properly s i dipped maybe 1/3 (the base).

The pot was on the highest setting. Last time it was much colder and I had turned the heat down a bit with great results.

I had smoked the mold the first time with a lighter. It's only needed the once, correct?

I used old cast and lubed BP bullets as flux.

When I mentioned the ring I mean the cast RB has a ring around it because the mold wouldn't close al the way.

The lead I'm using is from old lead piping so it's about as pure as can be they say.

[Omnivore]

I don't know how much casting you've done, so I'll start with basics. First; your mold should never, ever look like that inside.

Thoroughly clean and re-smoke the mold. If lead is sticking to it a lot (rather than just a little smear at the sprue plate now and then), you're probably trying to run the mold too hot. I only see that on my molds late in a casting session when I'm going pretty fast and the mold is really getting heated. When that starts happening on the top between the sprue plate and the mold block, I'll back off the pace to let the mold cool down slightly. I usually don't have any problem with lead smear on an aluminum mold, but it happens more on the iron molds. I don't know why. Maybe I just see it more because of the color contrast.

Little bits of this and that will form between the mold halves in the regular process of casting and dropping bullets, and that will result eventually in your mold failing to close properly. You have to stop and clean it. If your bullets have been filling out real nice, leave the cavities alone and just clean the flats where they mate. Often a rag will be enough to get the little lead bits off.

To remove lead smear, you have to get the mold hot again, and then simply wipe it off with a rag. If the sprue plate is gouging the aluminum, remove it, place it on a perfectly flat surface with some fine carbide sandpaper and smooth it off on the bottom. You can do the same thing to the top of the mold block, making sure to keep it closed (and therefore perfectly aligned) while you're working on it.

If you're using a ladle, make sure you don't have dross on the top of the lead in the ladle. A bottom pour mold or a skimming ladle will help in this regard, but the main thing is have a clean pot.

I've tried dipping the mold, but my preferred method of pre-heating the mold is to start pouring lead into the cavities. Just start casting. The first "bullets" will be horribly deformed. Keep pouring until you get good bullets, then maintain that mold temp. It may take a while. When the bullets juuust start coming out slightly frosted rather than shiny, don't let the mold get any hotter. Right around that occurrence is about your ideal running temp.

Don't overheat your lead pot either. If the lead wants to turn purple on top, or you see purple on your bullets, your lead is way too hot.

This is a casting forum primarily, so you can find millions of words already written on all possible casting problems and how to solve them if you poke around a bit.

Clean the mold so at least the cavities look new inside. Some use Kriol on a swab for cleaning and to very, very lightly coat the insides of the cavities. This WILL result in bad (i.e. wrinkled) bullets at first. Keep casting and once the Kroil burns off enough, it will leave a carbonaceous coating and you'll get hundreds of good bullets.

[Maven]

Rod, I have a .454" Lee RB mold of the new design that has (had) the same problem as yours does, namely not closing tightly. I cured it, but it should have been returned to Lee Precision. As for the staining, did you thoroughly scrub the mold before casting? Did you inadvertantly get some lube in the cavities? Lastly, about smoking the mold, I do it as is necessary (with wooden matches). Btw, if you decide to return the mold to Lee, don't remove and polish the edges and underside of the sprue plate. By all means do that to a replacement mold.

[rodwha]

My lead was sorta purple looking, and I did notice several frosted balls. And that makes sense as I had cast when it was much cooler and had my pot set a bit lower and was doing well. This time I left it on high.

I skim off the dross and dump it onto an aluminum pan.

I did nothing to y mold before I cast with it this time (my second). What I understood was to smoke the mold the first time and you are done.

There shouldn't have been any lube in the mold.

[cali4088]

Pure lead when real hot looks purple and blue. Its just oxidation. That old piping is most likely pure lead. looks like Omivore gave you some good advice. take care!

[Omnivore]

You should lube the alignment pins of the mold. I've had dry ones stick and thus prevent the mold from closing consistently. Learn from my pain. A high temp grease is the way to go there, and just use a tiny amount so it can't migrate to your cavities. Same on the sprue plate pivot. You'll have to reapply after several sessions, or as needed to ensure easy, repeatable closing.

Buffalo Arms sells an expensive, but very nice, adjustable locking mold handle. It uses a "Vice-Grip" type locking and adjustment system, and it results in very consistent closure of the mold. You adjust it so it just closes the mold with regular pressure, and then it closes the same each time and maintains steady pressure without your having to squeeze once it's locked. In long casting sessions I can sometimes fail to close the mold consistently when using regular handles, and then your bullet diameter can become more inconsistent.

You'll get accustomed to the subtle clues; what your pot and bullets should look like when your temps are in the right range, and so it gets much easier as you do it more, and the frustration begins to slip away as you know what to expect.

You should not have to skim much dross off the pot in even a long casting session if your temps are right and you're "fluxing" properly. I started out skimming huge quantities of purple and blue dross, but now the lead that's in the skim can is miniscule - mostly just dirt and scrapings from the edge of the pot. There is the magic of alchemy involved in "reduction". That's when a hydrocarbon presence (I use wax, chopped into little pieces. Pine pitch chunks gathered on my long walks also works extremely well, and it's free, but just about any hydrocarbon source will do. Some smell better than others) introduces freed carbon atoms over the top of the melt. That carbon scavenges the oxygen from the dross, transorming it back into clean, shiny lead. Don't skim it off - turn it back into clean lead. Further; if you're using a bottom pour pot, you can tolerate some accumulation of dross, which floats on the top, for quite a while, as the clean metal is being extracted from the bottom. You can then reduce the dross back to clean lead as you are free to do so. VERY minimal skimming is all that should ever be needed, and a thorough cleaning of the empty pot now and then. The latter is no problem if you use more than one alloy, as you're emptying the pot now and then anyway. Ingot molds are a must for such things if nothing else.

"Fluxing" and "reduction" are actually different processes and use different chemistry, but don't tell anyone.

One DISadvantage of a bottom pour pot is that your lead exit pressure constantly changes with the level of the melt in the pot. RB molds don't like a full pot (high pressure) as they tend to turn the squirting lead around and throw it back out the top of the mold. You find there's an ideal level, but maintaining it of course would mean that you're stopping and adding lead more often, so you put up with some variance.

[rodwha]

Hmmm….

So I have TONS of Gulf wax, which I was told makes a great fluxing material. How much should I use for my 4 lb pot if full?

I'm skimming off quite a bit of stuff. I end up with so much it makes me wonder how I had lead enough for the balls I cast!

[Omnivore]

How much to use? About enough to cover the surface of the lead as the wax melts, say a couple of pea sized chunks. It'll light up and burn off pretty quickly of course. And after that the lead will begin to oxidize again. When you believe you can't take it anymore, throw in some more wax. Everyone has their own methods. Once you see what's happening you'll come up with your own rhythm.

If you haven't thrown out the yellow, blue and purple skim, you can probably re-heat it at some point and reduce it back to clean lead.

About all that needs to be skimmed and thrown out is some ash-like material and dust-like stuff (highly scientific terms here) or oxides/scale from the pot itself. We're talking like a thimble full or less of light powder now and then. Practically no lead gets thrown out. Again; a pot that's too hot will oxidize your lead like crazy and it will be turning colors even as it's being poured. That's way over the limit. Some oxidization is inevitable, so long as there's an oxygen atmosphere exposed to molten lead, but now you know how to reduce it back to good metal. Some people leave a layer of sawdust over the clean lead to keep a more or less reducing atmosphere for a longer period. That kinda works, but it will leave more ash on top. Try it and see what you think.

Maybe now that you've tried the far-too-hot method, see if you can find the too-cool zone for the pot. It may surprise you, but then finding that balance of melt temp and mold temp, and getting the mold surfaces to take a good fill-out takes some doing. Fortunately a round ball mold is most forgiving as it has no corners to fill out-- You can pour at a fairly low melt temp and still get good RBs.

[rodwha]

I've often sifted through some of what I've pulled out to get what's clearly lead back into the pot for next time. I had no idea that quite a bit of that was useable lead. It didn't feel heavy to me.

I'll try adding Gulf wax in fair sized chunks next time instead of tossing in several lubed BP bullets, which may very well be nowhere near enough fluxing material.

And it only stands to reason to turn the dadgum heat down after the lead has melted.

Thanks for the help all!

[Hanshi]

For aluminum molds I simply lay them on the top edge of the melting pot. Only an edge needs to be immersed in the lead, anyway. Make sure you lube the locating pin with bullet lube. To keep lead buildup off the mold top just take a damp cloth and touch the top of the hardened puddle on top. Then use a WOOD dowel and gently tap the plate open. This procedure will produce good bullets without wrecking the mold. Also, just consider the first few balls as culls to finish heating up the mold.

[Fly]

So much info.Keep simple, I heat my mold on a hot plate & spray my molds with dry grafite chain
lube, inside the mold cavitys & on the bottom spur plate.I have had all those problems in the past, but no more.

Fly PS I also use saw dust to flux, but skim it off the top.[smilie=1:

[Southron]

Aluminum is a sorry material from which to make a bullet mould, Lee Mould's great virtue is that they are inexpensive.

Hang in there, you will get the problems worked out. Brass and Iron moulds are much better to use even though they are more expensive.