Aluminum moulds - whcih type to use?

[trk]

What type of aluminum would be best for making moulds (and why)?
(I have both mill and lathe.)

[Greg5278]

I used 6061 aluminum, and it machines fine, but won't last. They tell me 7075 is better, but I haven't used any. From my experience with the Aluminum, I will be making all of my molds from 65-45-12 Durabar cast iron. It machines into dust, won't wear out as quick, and does not have the same heat expansion problems.
Greg

[onceabull]

If "2024 T3" is meaningful to you,might consider that,as it is what Rapine uses for alum.blocks.. good luck ..Onceabull

[Buckshot]

...............I also think that NEI uses a 2000 series aluminum. Problem with 7075 and/or 'Fortral' is that lead casting temps are very close to aluminum annealing temps, so any hardened aluminum won't stay that way for long.

..............Buckshot

[felix]

If it were me, and emphasis placed on me, I would get that aluminum designed by Mercedes for exhaust manifolds. It is very unique in composition, and actually can be molded with extreme accuracy. Easy therefore, to mold the blocks before cutting and boring. Won't warp, obviously, during normal casting operations. ... felix

[andrew375]

I just us whatever is in the bar store, don't know what grade it is. Machines well and some moulds I've cut have churned out thousands of bullets without any signs of wear. If I were mould making for money I'd probably go for something a bit more sophisticated purely for better machinability.

[trk]

It's amazing what one can learn in a few minutes from others!

On another board Veral Smith recommended 2024 T 351 ! He mentioned it lost some of it's hardness after being subjected to casting temperatures as well.

I see a pattern here.

THANKS for EVERY response - this is like a puzzle - fitting together what works, what works well, and what doesn't work after a period of time.

[44man]

Felix has the idea! Use the lost wax process, make ceramic molds and cast the boolit mold complete. Knock it out of the ceramic, clean it up and cast boolits. Could be used with cast iron, brass or aluminum.
Anyone have a spare foundry in the basement we can start with?

[trk]

I couldn't get the 2024 locally, so I got 12' of 6061-T6 for under $52, will pick it up next week.

Looking at the Lee 6 holer - it looks like a 5/16 groove down each side and 5/16 OD bullet shaped locators on each end.

Plan (initially) is to cut 4 three foot sections to make handling easy - chop saw should do it with clamping. Then to cut the grooves - good job for horizontal mill if I had one. Hmmmm.