Alum. Molds

[686]

i see 3 different mold makers listing 3 different alum. i was told lee is even another.

2024
6061
7075

what is the best to not ding up the mold, cast better, easer, and last longer. one has to be harder and one softer. who knows what is best?

[theperfessor]

Best is a relative term. 6061 is the softest but it is also the least expensive and the most widely available. 2024 and 7075 are harder but a lot pricier. If you take good care of a mold made from 6061 it will last a long time, but it is more prone to dinging up.

My first mold was made from 6061 and it works fine, but since I want to make the best molds available I have switched to 7075. I just bought two 3/4" x 2" by 72" bars of 7075 last week and paid about $285.

Lee couldn't afford to use this and make 6 cavity molds for $40. I bet they are using some flavor of 6061.

[BABore]

2024 Aluminum is alloyed with copper to allow it to be solution heat treated. In a hardened state, it can be almost as hard as steel. It has poor corrosion resistance and subject to intergranular corrosion. Machines well.

6061 Aluminum is alloyed with silicon and magnesium. It is also solution heat treated. Its heat treated strength is less than the 2000 or 7000 series alloys. Excellent formability and machining qualities and very corrosion resistant.

7075 Aluminum is alloyed with zinc and smaller portions of magnesium, copper, and chromium. It heat treats to a very high strength. Like 2024, it has poor corrosion resistance.

When I first started making molds, I followed the big boys and used 2024 alloy. It cherry cut just fine and I had no problems with it, other than the cost. It was 3 times higher than 6061. We normally use 6061 for a non-critical material on welding fixtures. On a whim, I decided to make a few block sets from 6061 to see if there was any difference. It cherryed basically the same. Where I did notice a big difference was in cleaning the mold of cutting lubricant. The 2024 seemed to be more porous and suck in the lube. It only came out after several cleanings. The 6061 didn't exhibit those traits. From a casting/use standpoint, I haven't really seen a difference. Both alloys are solution heat treated to similar hardnesses. Both anneal quite well after several casting sessions. Both alloys are of similar hardness in their annealed state. I chose 6061 based on cost and easy availability. As far as 7075 goes, I do think it has some better attributes over the other two. At least as far as strength goes. Having never used it, I don't know how it handles the repeated heating and cooling cycles. Since all of the aluminums melt at slightly above 1,200 F, I would think they all anneal, or soften at similar points. 7075 may just be a tad better than the others at hot strength, but that does not necessarily mean it has any better hot hardness. All of these alloys are better than what Lee uses. None of them are comparable to steel or iron molds. Any type of aluminum mold will be subject to mishandling, operator error, lack of attention to problems, and other cub bear with boxing gloves tendencies.

[StarMetal]

2024 Aluminum is alloyed with copper to allow it to be solution heat treated. In a hardened state, it can be almost as hard as steel. It has poor corrosion resistance and subject to intergranular corrosion. Machines well.

6061 Aluminum is alloyed with silicon and magnesium. It is also solution heat treated. Its heat treated strength is less than the 2000 or 7000 series alloys. Excellent formability and machining qualities and very corrosion resistant.

7075 Aluminum is alloyed with zinc and smaller portions of magnesium, copper, and chromium. It heat treats to a very high strength. Like 2024, it has poor corrosion resistance.

When I first started making molds, I followed the big boys and used 2024 alloy. It cherry cut just fine and I had no problems with it, other than the cost. It was 3 times higher than 6061. We normally use 6061 for a non-critical material on welding fixtures. On a whim, I decided to make a few block sets from 6061 to see if there was any difference. It cherryed basically the same. Where I did notice a big difference was in cleaning the mold of cutting lubricant. The 2024 seemed to be more porous and suck in the lube. It only came out after several cleanings. The 6061 didn't exhibit those traits. From a casting/use standpoint, I haven't really seen a difference. Both alloys are solution heat treated to similar hardnesses. Both anneal quite well after several casting sessions. Both alloys are of similar hardness in their annealed state. I chose 6061 based on cost and easy availability. As far as 7075 goes, I do think it has some better attributes over the other two. At least as far as strength goes. Having never used it, I don't know how it handles the repeated heating and cooling cycles. Since all of the aluminums melt at slightly above 1,200 F, I would think they all anneal, or soften at similar points. 7075 may just be a tad better than the others at hot strength, but that does not necessarily mean it has any better hot hardness. All of these alloys are better than what Lee uses. None of them are comparable to steel or iron molds. Any type of aluminum mold will be subject to mishandling, operator error, lack of attention to problems, and other cub bear with boxing gloves tendencies.

The 7075 T6 is what M 16 receivers are manufactured from.

Joe

[BABore]

The 7075 T6 is what M 16 receivers are manufactured from.

Joe

So! Pull the receiver, dip it in your lead pot for a 20 count, and then cast some ingots for a few hours. Then drop it on the floor or hit it with yer club a time or two. Now see how it works with some proof loads. Waiting on your full report.

[StarMetal]

So! Pull the receiver, dip it in your lead pot for a 20 count, and then cast some ingots for a few hours. Then drop it on the floor or hit it with yer club a time or two. Now see how it works with some proof loads. Waiting on your full report.

Shoots one hole ragged groups afterwards bwahahahahahaha

Joe

[theperfessor]

Just a fine point to add here. I've found that with aluminum alloys it is important to pay attention to more than the alloy designation (6061, etc.). The last group of alphanumeric characters (T651 for example) designate the thermal and processing history, which is reflected in the material's hardness, formability, resistance to warping when machined, etc.

Since I'm not a black rifle guy I didn't know what alloy they were made from but it is a good fact to know.

[badgeredd]

2024 Aluminum is alloyed with copper to allow it to be solution heat treated. In a hardened state, it can be almost as hard as steel. It has poor corrosion resistance and subject to intergranular corrosion. Machines well.

6061 Aluminum is alloyed with silicon and magnesium. It is also solution heat treated. Its heat treated strength is less than the 2000 or 7000 series alloys. Excellent formability and machining qualities and very corrosion resistant.

7075 Aluminum is alloyed with zinc and smaller portions of magnesium, copper, and chromium. It heat treats to a very high strength. Like 2024, it has poor corrosion resistance.

When I first started making molds, I followed the big boys and used 2024 alloy. It cherry cut just fine and I had no problems with it, other than the cost. It was 3 times higher than 6061. We normally use 6061 for a non-critical material on welding fixtures. On a whim, I decided to make a few block sets from 6061 to see if there was any difference. It cherryed basically the same. Where I did notice a big difference was in cleaning the mold of cutting lubricant. The 2024 seemed to be more porous and suck in the lube. It only came out after several cleanings. The 6061 didn't exhibit those traits. From a casting/use standpoint, I haven't really seen a difference. Both alloys are solution heat treated to similar hardnesses. Both anneal quite well after several casting sessions. Both alloys are of similar hardness in their annealed state. I chose 6061 based on cost and easy availability. As far as 7075 goes, I do think it has some better attributes over the other two. At least as far as strength goes. Having never used it, I don't know how it handles the repeated heating and cooling cycles. Since all of the aluminums melt at slightly above 1,200 F, I would think they all anneal, or soften at similar points. 7075 may just be a tad better than the others at hot strength, but that does not necessarily mean it has any better hot hardness. All of these alloys are better than what Lee uses. None of them are comparable to steel or iron molds. Any type of aluminum mold will be subject to mishandling, operator error, lack of attention to problems, and other cub bear with boxing gloves tendencies.

Bruce,

For the record, a lot of the aftermarket Street Rod Accessories are made from 6061 because it anodizes better than the 2000 or 7000 series and as you say it appears to be more corrosion resistant. Also, I've built a lot of platic injection molds for prototype and limited production plastic parts. The 7075 T6 is the aluminum of choice because of it hardness and machinability as well as its ability to take a good finish (shine). We have built prototype tooling using the 6061 for polypropylene parts too since it isn't very abrasive and doesn't require very high heat to mold correctly, and it does wear well in that application.

Edd

[StarMetal]

Bruce,

For the record, a lot of the aftermarket Street Rod Accessories are made from 6061 because it anodizes better than the 2000 or 7000 series and as you say it appears to be more corrosion resistant. Also, I've built a lot of platic injection molds for prototype and limited production plastic parts. The 7075 T6 is the aluminum of choice because of it hardness and machinability as well as its ability to take a good finish (shine). We have built prototype tooling using the 6061 for polypropylene parts too since it isn't very abrasive and doesn't require very high heat to mold correctly, and it does wear well in that application.

Edd

The M16's and AR15's seem to take a very durable long lasting finish.

Joe

[beagle]

Supposedly, 6061 machines better as well./beagle

[badgeredd]

The M16's and AR15's seem to take a very durable long lasting finish.

Joe

Sorry Joe, but a polished finish isn't the same as a chemical coating. Anodizing requires a semi-porous material to bond to...therefore... 6061 must be a little more porous. I asked a couple manufacturers what grade aluminum they used and why. Their answer was that 6061 took anodizing better than 7075. I'd think that the zinc in 7075 may have some bearing on its ability to be anodized too, but that is just a guess on my part.

Edd

[StarMetal]

Sorry Joe, but a polished finish isn't the same as a chemical coating. Anodizing requires a semi-porous material to bond to...therefore... 6061 must be a little more porous. I asked a couple manufacturers what grade aluminum they used and why. Their answer was that 6061 took anodizing better than 7075. I'd think that the zinc in 7075 may have some bearing on its ability to be anodized too, but that is just a guess on my part.

Edd

Sorry about what, you saying that AR's and M16's don't have somewhat of a durable finish. I never said it had to be anodized.

Joe

[Marlin Hunter]

I assume your are a beginner (like me)

My opinion is to get the lower price Lee because they will work good enough for a beginner and if you damage one, it's not the end of the world or your wallet. Make your mistakes and learning curve on something inexpensive. When you get experienced you can buy more expensive molds or another Lee.

[beagle]

The finish on M-16s is not that great. I wore a couple out in VN. Started out fairly new and the beating, rain and mud turn the finish into junk in 6 months. Now, if it stays in an arms room all it's life, you're all right but in normal GI field use with not much care on the outside and no external protection, that finish don't hack it.

Don't remember what the finish is on the Barretts but I saw four that had gone through Desert Storm and they were ready for some major refinishing too./beagle

[StarMetal]

The finish on M-16s is not that great. I wore a couple out in VN. Started out fairly new and the beating, rain and mud turn the finish into junk in 6 months. Now, if it stays in an arms room all it's life, you're all right but in normal GI field use with not much care on the outside and no external protection, that finish don't hack it.

Don't remember what the finish is on the Barretts but I saw four that had gone through Desert Storm and they were ready for some major refinishing too./beagle

They have more finishes available then when the came to use in Nam. People always refer to war. We're not in a war and I'm talking us civilians. War is harsh on everything. For our civilian use, as you stated, they finishes today are just fine.

I would imagine sand would wear any finish off.

Joe