03-18-2012, 07:50 AM
Every part you make in a machine shop has different requirements for the materials because of how the part may be used. IMHO, there is never going to be "just one or even two" materials that cover even half of the parts you'd make.
That said, if you forced me to choose, I'd probably go with THREE materials. I'd get 360 half-hard brass, 6061-T651 aluminum and pre-heat treated 4140 as my three. You can quickly machine the brass or aluminum with any tools, and the reason I would would want both are that aluminum doesn't have much strength in small threads, brass does better and will bend before it breaks. In steels, the pre-treated 4140 can serve in most any capacity that a 1018 or 1020 steel would, but not often the other way around. The fact that you can get it pretty hard and it's starting out at 28-32Rc gives it more range of application. It machines pretty good with carbide tooling, something I'm lucky to have lots of here. I find that the chrome in it lends a little more corrosion resistance too.
That said, if you forced me to choose, I'd probably go with THREE materials. I'd get 360 half-hard brass, 6061-T651 aluminum and pre-heat treated 4140 as my three. You can quickly machine the brass or aluminum with any tools, and the reason I would would want both are that aluminum doesn't have much strength in small threads, brass does better and will bend before it breaks. In steels, the pre-treated 4140 can serve in most any capacity that a 1018 or 1020 steel would, but not often the other way around. The fact that you can get it pretty hard and it's starting out at 28-32Rc gives it more range of application. It machines pretty good with carbide tooling, something I'm lucky to have lots of here. I find that the chrome in it lends a little more corrosion resistance too.