TRX
02-20-2011, 12:12 AM
I've been using 6061 aluminum from my junkbox to make molds. However, I've been wondering about making them out of brass.
Since I don't have any suitable brass, I checked onlinemetals.com. They have 3/4x1-1/2 red brass flat for $38.16 per foot. That would make three pairs of blocks about 1.4" to a side after sawing the finish cutting. With shipping and handling, just the metal would be about $20 per pair.
Leaded brass was $42 per foot, and copper was $57.
Now I begin to understand why brass blocks are so expensive...
2024 aluminum was $17.04 for the same size. 2024 holds its strength better than 6061 at mold temperatures, and it machines to a mirror finish with ordinary tools. It's not nearly as common as 6061.
6061 is your bread-and-butter extruded aluminum. It machines well, and the price is right - $6.61 for the same 3/4x1-1/2x12" size above.
McMaster-Carr has 12L14 free-machining leaded steel bars, 1-1/2x1-1/2", for $35 per foot. One of those bars could make six pair of mold blocks. I was never all that impressed with the machineability of 12L14, but it might be worth a try.
McMaster has gray cast iron listed in some odd sizes. The problem with iron is that depending on how it's made, it can be anywhere from hard enough to dull carbide tools to nearly soft enough to chew with your teeth... and "gray cast" spans a large portion of that. (the difference between "steel" and "iron" is more how they're made than their chemical composition... ferrous metallurgy is more crystallography than chemistry) Anyway, I decided to skip the mystery iron.
Mountain Molds lists Durabar as an option, which is a very ductile, free-machining iron. I went to the dura-bar.com web site. They list 3/4x1.5" ductile bar, but I couldn't find any price list. Mountain wants substantially more for Durabar molds than brass ones, though...
I think I'll stick with plain old 6061 aluminum for now...
Since I don't have any suitable brass, I checked onlinemetals.com. They have 3/4x1-1/2 red brass flat for $38.16 per foot. That would make three pairs of blocks about 1.4" to a side after sawing the finish cutting. With shipping and handling, just the metal would be about $20 per pair.
Leaded brass was $42 per foot, and copper was $57.
Now I begin to understand why brass blocks are so expensive...
2024 aluminum was $17.04 for the same size. 2024 holds its strength better than 6061 at mold temperatures, and it machines to a mirror finish with ordinary tools. It's not nearly as common as 6061.
6061 is your bread-and-butter extruded aluminum. It machines well, and the price is right - $6.61 for the same 3/4x1-1/2x12" size above.
McMaster-Carr has 12L14 free-machining leaded steel bars, 1-1/2x1-1/2", for $35 per foot. One of those bars could make six pair of mold blocks. I was never all that impressed with the machineability of 12L14, but it might be worth a try.
McMaster has gray cast iron listed in some odd sizes. The problem with iron is that depending on how it's made, it can be anywhere from hard enough to dull carbide tools to nearly soft enough to chew with your teeth... and "gray cast" spans a large portion of that. (the difference between "steel" and "iron" is more how they're made than their chemical composition... ferrous metallurgy is more crystallography than chemistry) Anyway, I decided to skip the mystery iron.
Mountain Molds lists Durabar as an option, which is a very ductile, free-machining iron. I went to the dura-bar.com web site. They list 3/4x1.5" ductile bar, but I couldn't find any price list. Mountain wants substantially more for Durabar molds than brass ones, though...
I think I'll stick with plain old 6061 aluminum for now...