Thread: Best Mild Steel for Machinability

I got 12L14 and have done some machining on it, in my experience it doesn’t rust for me near as bad as others seem to experience.

It will rust if allowed to but I just faced off some a few weeks ago and set it aside and it’s still not rusty even sitting in my non heated garage.

Don’t be afraid of it, and as said you can get a nice surface with very little effort and it’s easy on your tooling

The biggest problem with the really nice machining steels is availability. Mostly they are only available in very limited shapes - round, square, hex. Otherwise you are left with 1018 and A36.

A36 can have a real shiny finish if it's run fast enough. I don't know how you'd do that with a tiny tool though.

I made a bunch of torque converter shells from 13" 1018 and I'd take a .01" finish pass at 1500 RPM (as fast as I'd feel comfortable with that machine). Real shiny.

Before I went off on my own, I worked in an engineering job and had a lot of free time to read tech books. The highest rated steel for machineability was 12L14 with tellurium, a big step higher rated than plain 12L14. My cubicle mate was not at all familiar with types of steels and machineability ratings. His speciality was time study. In my readings, I mentioned to him about 12L14 with tellurium and he must have remembered it. Our main material was a nickel based super alloy used for jet turbine hot section blades, similar to inconel, terrible to machine. My friend actually only knew one steel alloy, the one I mentioned to him, 12L14 with tellurium. A machining vendor was talking with him about doing some work for us. My friend told the vendor the blade alloy was hard to machine, certainly not 12L14 with tellurium. At that point the machining vendor exclaimed "you know your metals!"

Dad used to run a lot of 1215. Cut very well at 800 SFM and surface finish was acceptable. 4140 will always give a better part, but, depending on tooling, you may have to slow things down.

Personally, i wish 1144 Stressproof was available in blocks or sheets.