Is 6061 or 2024 better for a mould?

[fatelvis]

Which aluminum is better for making a mould? If they have strong/weak points, could you please describe each? Thanks-

[theperfessor]

6061 - cheap and widely available, cuts good but very soft.

2024 - more expensive, harder to get, cuts good, harder.

7075 - more expensive, harder to get, cuts great, harder. IMHO the best for long term strength and endurance.

Just my $0.02.

[Marvin S]

I would say either is fine but more important is the heat treat. Go for at least T-4, with T-6 being better yet. I like 7075 T-6 myself.

[fatelvis]

Ahhh, I forgot about the heat treating! Which is harder: 6061 T6 or 2024?

[Marvin S]

You would need the T# after the 2024 but usually T-4 is about the highest the 2024 comes in or is practical to heat treat to.

[fatelvis]

Ok, 6061 T6 or 2024 T4?

[303Guy]

Hang on. We're talking heat treating an alluminum alloy for a hot mold? Wouldn't the question be more of which alloy keeps its strength better (or gains more strength) after heating to casting temperature or above?

[fatelvis]

I'm trying to determine which of two company's molds (that will remain anonymous) are of a harder alloy, and thus will last longer. Just trying not to "bash" anyone.

[Willbird]

A bit of google suggests that heating 6061t6 past 275 degrees F will cause it to no longer be t6...IE it will anneal it.

Bill

[StarMetal]

Buckshot and I spoke on the phone one time about heat treated aluminum for use in a mold and if my memory is right we both concurred that the heat treat would leave considering molds get plenty hot.

As far as wearing an aluminum mold out, well those soap soft cheapo Lee's last a mighty long time with proper care. The bullet shrinks in the cavity so it should just fall out, where's the wear there? I see the wear mainly being the sprue plate damage and yes, the side of the cavity that supports the bullet when the sprue plate is cutting the sprue.....but I haven't seen evidence of that.

[Marvin S]

Most Alum precipitation hardens at about 920F and then can be artificially aged at about 340F when shooting for T-6. For making a mold from the start I would choose a T-6 as it machines cleaner and better than the soft stuff. Just for kicks I will rockwell test one I made from 7075 T-6 that has been used and see how true it is. I do know that many jet engine exhaust outer tail pipes are alum and they get pretty hot.

[Tom-ADC]

Regardless of which aluminum you pick, I think you will find the harder the material T4-T6 the easier it is to cut with power tools the softer "O" condition tends to gaul and clog the cutting tool up. At least when trimming or routing in a manufacturing area. Some of the aluminums are available in the T3 condition which is actually harder than T4.
Would like to see progress to finished when you start.

[JeffinNZ]

For working 7075. I made a pair of sprue plates for my Lyman .22 moulds from 7075 and it works wonderfully well. THEN someone asked me to make a sprue plate for them and handed me a piece of alum. of unknown parentage that worked just awful. Horrible stuff.

[fatelvis]

What kind of aluminum does Lee use for thier molds?

[theperfessor]

Probably 6061 from the hardness and price.