Austenitec stainless steels (300 series) are generally tough and gummy. Work hardens easy. Martensitic stainless steels (400 series) are harder, but the higher carbon to chromium ratio makes them more free machining. Precipitation hardened stainless (17-4, 15-5) are almost always machined in an annealed state, and machines like 300 series but is somewhat tougher. Also work hardens.
I mill a lot of 316/316L, 304, and some 302, 15-5, & 400 series.
I don't do much lathe work but machining is the same turning or milling. Stainless with high chromium content (300, ph) require slow speeds & high feeds. The tool needs to cut under the hardened layer. Stainless is also a poor heat conductor, so the heat generated during the cut will tend to remain at the cutting edge of the tool rather than be carried away with the chip. Flood coolant is generally the only way to keep the tool from burning up. Some shops are successful with dry machining. When milling I use pm roughers for hogging and carbide endmills for finishing. For turning I use carbide inserts for roughing & finishing.
For your specific machining needs just look the Machinery's Handbook or any machining reference book and you'll find everything you need to know.
Hope this helps.  |