Aluminum molds

[jednorris]

I have used steel molds for years and never had a problem with heat retention. I have avoided aluminum molds up to now but now I have to use one. I have a four cavity Aluminum NOE mold for a.38 Cal. 312 gr. bullet. I am having trouble keeping the mold hot enough to cast good bullets. I am heating the mold on a hotplate, not the spiral element type, but the flat top type. I heated the mold as high a temperature as the hot plate would go, then poured the lead into the mold as it was ON the hotplate. I tried filling just two cavities, but I still got wrinkles. Normally when I cast with one cavity steel molds, I can pour them and drop them so long as I work steadily. I am thinking that I might have to pour into the mold as it is being heated with a blow torch. My lead is at 770* and that is as hot as my poor old pot will go and the lead is coagulating during the pour. Can I ruin the mold by overheating?

[35 Rem]

Sit it on top of the molten lead in the pot for a minute or so. The lead should not stick to the bottom of the mold at all when you lift it up. If it does, let it sit there for a while longer. Then when you get the mold itself up to temp, put the end of the sprue plate in the melt for 20 or 30 seconds. At this point it should be ready to go. I've never owned a hot plate in my life and the above method is what I use entirely.

I always cast at about the same temp you are talking about. I set my Lee 20lb pot wide open and use a PID set at 800 degrees to control it. It never reaches the 800 though and operates more like 750 to 780 at best. I try to keep dumping sprues back in often enough that variations in temperature don't swing too far from the target temp. The majority of my molds are aluminum and this works well for me.

[Delkal]

My problem with aluminum molds is they get way too hot! Aluminum conducts heat faster and does not hold heat like iron so if I cast too fast it takes a long time till the sprue hardens enough to open it. I often have to take a break with the mold open or even passing it over a damp rag.

Sounds like you just needed a few more pours to get the mold temp up. I like to cast hot but never needed 770 degrees. 725-750 max is my sweet spot for nice frosty bullets. Some people and books would even say that is too high but it works for me.

[BJung]

35 Rem makes a good point I forgot. I first add heat to my mold with a propane torch. Then, I put the edge of my mold into the molten lead as 35 Rem said to test it. Until that molten lead doesn't stick to the mold, it's not ready. Wrinkles might also be a mold contamination problem.

[poppy42]

I have a hard time understanding why you can’t get and keep an aluminum mold hot enough to cast good boolets! Typically the problem is that they get to hot! When I cast with aluminum molds, with 2 cavity I cast with 4 at a time, 6 cavity I use 2. That way I can switch molds and let them cool down and I don’t have to stop casting! I’m at a loss to figure out why you can’t get them hot enough’

[jednorris]

I tried it again today. I sprayed the mold with carburetor cleaner then washed with Dawn. I waited until the hotplate had fully heated the mold, then poured. Wrinkles. I then left the mold ON the hotplate and poured, still wrinkles. I have an old top ladle Lyman lead pot and have it turned up all the way. I truly do not know the temperature, but it has been fine for my 480 gr. .40 cal. bullets in a steel mold. During the pour, the lead starts to coagulate about the third cavity of the four-cavity mold. I am beginning to think the lead is not hot enough. I am thinking of going back to a lead pot on the stove, but I have no way of gauging temperature.

[FLINTNFIRE]

For a long time I made my bullets over a small fire and then a electric range and a coleman gas stove , never had a thermometer .

Let the lead get melted and started casting , now I have a thermometer which seems to have lost its calibration by well over 100 degrees .

Have several melting pots that have just a dial and 1 with a pid , I do not find a real need to know temp. as long as lead melts and is hot enough to flow while casting .

I find for the multiple cavity molds that a hot plate is a fantastic piece of the process , mine are solid top hotplates and using medium has always been enough .

I use bottom pour pots brass , steel and aluminum molds and do not experience these issues , it does sound like your pot is not hot enough along with mold not being up to temp , it may be time to get a new melting pot .

Are you pouring lead with a big dipper in 1 pour or using a smaller ladle and trying to do all 4 cavities at 1 time ? Still sounds like there is not enough heat in the process .

[nuclearcricket]

I have used a variety of aluminum molds over the years. Best way to get them to cast good bullets is to coat the cavity with carbon. One of the grill lighters is the easiest to use, it keeps your fingers away from the flame and it can be easily moved around the cavity. Yes it kind of makes the mold blocks look bad but a good coat really improves how well they work.It doesn't take much to heat up aluminum molds. They should be dropping good bullets in a few casts.
Sam

[country gent]

Jed, wrinkles may not be caused just by being to cold. plugged vents or inadequate venting can also cause wrinkles and poor fill out.Try adjusting the sprue plate a little to allow better venting. Another trick is to stone a small 45* bevel on the tops of the blocks so there is a fine groove under the sprue plate. This just need to be enough of a line to see. use a small fine stone. Also clean the vent lines with a point on a bamboo skewer.

Another area to check is the actual pour, to slow a fill can give issues especially with long bullets. You might give a ladle a try to see if the faster fill helps.

I still cast over a flame (propane burner) I cast my 360 grn 38s at 750* these are in a brass 2 cavity mould. My ladle has the spout opened up to .201 dia and I pour a full stream in. I fill the ladle and pour the full ladle into the vented trough letting the excess run back into the pot.

I would start by looking at how the mould is vented and fills.

[imashooter2]

Set the mold on the rim of your pot when you plug it in. When the lead is to temperature, the mold will be too.

[Mk42gunner]

0
I have used steel molds for years and never had a problem with heat retention. I have avoided aluminum molds up to now but now I have to use one. I have a four cavity Aluminum NOE mold for a.38 Cal. 312 gr. bullet. I am having trouble keeping the mold hot enough to cast good bullets. I am heating the mold on a hotplate, not the spiral element type, but the flat top type. I heated the m000old as high a temperature as the hot plate would go, then poured the lead into the mold as it was ON the hotplate. I tried filling just two cavities, but I still got wrinkles. Normally when I cast with one cavity steel molds, I can pour them and drop them so long as I work steadily. I am thinking that I might have to pour into the mold as it is being heated with a blow torch. My lead is at 770* and that is as hot as my poor old pot will go and the lead is coagulating during the pour. Can I ruin the mold by overheating?


I tried it again today. I sprayed the mold with carburetor cleaner then washed with Dawn. I waited until the hotplate had fully heated the mold, then poured. Wrinkles. I then left the mold ON the hotplate and poured, still wrinkles. I have an old top ladle Lyman lead pot and have it turned up all the way. I truly do not know the temperature, but it has been fine for my 480 gr. .40 cal. bullets in a steel mold. During the pour, the lead starts to coagulate about the third cavity of the four-cavity mold. I am beginning to think the lead is not hot enough. I am thinking of going back to a lead pot on the stove, but I have no way of gauging temperature.
Something doesn't sound right to me. How are you determining your lead is at 770 degrees if you have no way to of gauging temperature? Please do not believe what a dial setting says.

One way to check is to try to cast a bullet with one of your iron molds. If it works fine, if not check another thing.

Is this a new batch of alloy?

Remember to only change one thing at a time if you really want to know what is wrong.

Robert

[jednorris]

I have a friend that is loaning me a thermometer so I can check my lead. I am also going to try heating lead on the stove so I can gradually increase heat. I truly appreciate all the advice I am given. I probably will not be able to continue testing until the first of the week, GOTA SHOOT SUNDAY.

[Bent Ramrod]

I treat aluminum moulds like nuclearcricket describes. A thin layer of carbon, whether soot from a lighter or candle, or a spray-on mould prep composition, retards the heat transfer out of the mould cavities long enough to keep the castings liquid for a short time after the cavity is filled. I’ve never managed to apply a coating thick enough to change the dimensions of the boolit. I imagine this could be accomplished with a lot of heavy spraying, but I follow the instructions and it doesn’t happen. The soot seems to be self-limiting; in any case, once I see it’s on there, it’s time to start casting.

I do find that even with the coating, I need more heat on the melter, especially if the aluminum mould is a multicavity one. But without the carbon layer, if I cast quickly enough and hot enough to fill, I get castings that frost heavily and shrink away from the cavity surface. It looks like an incomplete fillout (which it is) but with everything too hot instead of too cold. This can reduce the output of a four- or six-cavity aluminum mould into what could be expected from a double- or single-cavity iron mould, with a lot of culling into the bargain.

If the metal is still so hot that the sprue cutter smears or tears the bases, I turn the mould (with solidified but still soft sprue) over and touch the sprue to the rim of the metal oven pan I have my melter in to catch splashes and other casting effluvia. The metal rim sucks the heat out of the lead without cooling the sprue plate too much, then I turn the mould back over and cut the sprue. It speeds up the casting significantly, and the quality of product is better.

A damp rag also works for this but I found I had to keep adding water as it boiled away, and it resulted in a thin surface rust on the sprue plate after the casting session was finished. The oven pan is large and thin and dissipates heat just as well, without complications.

[gwpercle]

You stated " ... the lead is coagulating during the pour. "

Do you mean the lead is hardening while filling the boolit mould cavity ?
If so ... something isn't right . I can fill my dipper from a Lee Magnum Melter , fill 3 cavities and still have to wait a few seconds for the last sprue to completely harden before cutting the sprue . The Lee control dial is set on the number 7.5 at first , then back to 7.25 when the mould gets hot -hot and boolits start dropping frosty and I don't use a hot plate ... or have a thermometer
How old is your pot ... I wonder if the control dial or heating element is going wonky !
Good Luck finding the problem ...
This is why us Boolit Casters get gray hair !
Gary

[john.k]

A cheap hand held IR thermometer solved my problems .....I was casting too low temp ...........Iron molds were OK ,but ally took forever to cast cleanly ........now ,at the correct temp,I have used new Lee molds straight from the packet ,no cleaning at all,and they worked perfectly.................One thing about too low temp,there was never any oxide ...no trace of color or skin .............at the higher temp ,I get oxide.

[Recycled bullet]

I wonder if your sprue plate is not hot enough ? Aluminum molds can be annoying to get up to temperature . Here are some ideas Use your kitchen stove to heat your mold or use a metal coffee can to make a mold oven on your hot plate. Use some two-cycle oil soaked on a cotton rag to maintain the mold and also function as a temperature check. The two-cycle engine oil rag will smoke when wiped on the mold at the correct temperature.

Yes it is possible to overheat and destroy your mold so don't walk away for 30 minutes while the mold is heating up.

That's about the only way I have managed to mess it up. I did it once my inattention led to damage. I was heating up my mold to cast, then I went to check something, then something else happened, then something else happened, then when I went to go check on the mold maybe 30 minutes have gone by and I found that I had cooked the bluing off of this sprue plate. The solution was easy I just ordered another Sprue plate and I polished the faces of the mold with a strop glued to a piece of wood problem solved mold
works great now.

Or you can do what I do I Ladle cast cast bullets over a turkey fryer out of a 1 qt saucepan using the RCBS ladle. In order to get my mold up to temperature I stick the mold directly into the path of the flames then I use the oily rag to clean and verify temperature. When I pour lead with the ladle I am also pouring Heat.

[MT Gianni]

NOE preservative is hard to remove from molds. Make sure that you do the three warm up and cool down cycles.

[kevin c]

I got advice here to shoot for a mold temp around 400° (I actually use 420°). A K type thermocouple inside a cavity lets me know the blocks on my coil hot plate have done the job. The hot plate actually wasn’t doing the job very well even at high setting until I built an insulated “garage” to park the mold in while it heated.

Edited for clarity