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01-15-2008, 07:37 PM. For the limited number of times I've worked with them, 303 leaves me with a fine turned but pewter colored finish while 304 leaves a mirror-like finish without trying very hard. This is with small nose radius carbide and low to moderate speeds and feeds.
304 is miserable. If it is possible, change to 303. If not, is it possible to relieve the bore so the whole 3/4" is not tapped. The other area to look at is taps that are specifically for stainless. Check the catalogs or suppliers, there are taps available that have a much shorter cutting area, and black oxide finish for stainless.
304 (18-8) is the most commonly used stainless steel. It's a totally different animal than 303. It's a pain in the butt to machine -- it work hardens if you look at it wrong. But 304 is highly corrosion resistant, and welds very nicely. I grab 303 stainless steel drops off Ebay -- almost always seen in rounds and hex.
SULPHUR!! sulphur is added to 303 stainless to make it cut like butter. Machinists hate 304 stainless because it is tough and gummy and wears out tooling. Sulphur is bad for welding…its Good for machining…but Bad for Welding. The cousin of 303 free machining stainless steel is 12L14 free machining carbon steel. The "L" in 12L14 indicates LEAD!!
01-26-2022, 10:40 AM. It's not any harder to turn than steel but it tends to stream and bird nest more than steel. Gets pretty hot too but all this depends on which series ss your talking about. Some ss alloys are considered free machining, such as those that are sulfurized, but that stuff tend to irritate your throat.
Tweet. #6. 10-31-2004, 04:47 PM. When you heat up 304 stainless, then water quench it, you actually anneal it, making it softer, not harder. The only way 304 hardens easily is work hardening, like when you push on it with a dull drill bit. So if you need a hard pin, use a steel with some carbon in it.
304 will generally produce long stringy chips. It is not absolute as 304 can be all over the map in machinability. While doing your turning job you will notice a huge difference in tool life. 304 is quite tough on tools, especially if your speeds and feeds are incorrect. 303 is much more forgiving and the machining parameter window is much larger.
303, 304 and 316 are Carpenter products I've used. Even their 316 is an easy machining grade. Unfortunately, in recent years Carpenter has become next to impossible to deal with in purchasing small quantities, most major players in stainless also have "special" free machining versions of their own which seem almost as good as Carpenter's.
Tweet. #1. 4140 P/H vs. 1144 S/P machinability. 04-25-2020, 09:01 PM. Would like to hear your opinions on how 4140 pre-hard cuts compared to 1144 stress-proof on a milling machine. I've milled plenty of 1144, 1018 CRS, 304, 303, but not one chip of 4140 ph. I'd like to use some on a project or two, but the whole pre-hard thing makes me want to ...
Milling a little off each side helps. Stress relieving at 190C / 374F in an oven if possible. Straightening using a press works if you go just beyond straight, flip the work and gently push it back a bit. You can stress relieve more than once. Always leave enough on the surfaces for light finish cuts.