Which Stainless Grade is easiest to machine?

I will be turning and milling some stainless steel bar for my
motocycle. Pieces are decorative only - strength not important.
Which of these grades will be easiest for my carbide tooling?
T-303
T-304L
T-316L
T-416
Regards,
Ed Ferguson
Reply to
Ed
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303 and 416 are relatively free machining and easiest to cut, 416 is heat treatable so see what meets your needs. 304 and 316 are nasty. 304 is cheap and lots of companies tend to use that instead of the free-er machining 303 but what they save in material they lose in machining/tool cost. It all comes down to what properties you need though.
JohnF
Reply to
JohnF
303 cuts like butter, but doesn't taste like butter. Next is 304, then 316, then 416. None are any problem for carbide. The down side to 303 is the surface finish never seems as good as the others because it tends to tear. The upside is it drills real easy.
Reply to
tomcas
304L is a free machining grade, 303 and 304L won't require carbide, HSS works just fine.
Reply to
Tony
Thanks John,
Now, between 303 and 416, do you know which is the most "rust proof"? I won't be heat treating or welding. Just need the easiest stainless to machine while having properties to take a high polish and hold up for outdoor, decorative usage on a motocycle.
Regards, Ed Ferguson
Reply to
Ed
Actually, 416 is better to machine than 303S. It is the best machining of all the stainless family, machines even better than 1212 steel. From personal experience, I've found that 303Se is slightly better to machine than 303S, and I've cut a considerable amount of each of them. Neither of these two are the best for corrosion resistance, but each will work just fine for your intended purpose. If you expect them to remain rust free, however, you should passivate them. Stainless is known to lightly rust, which passivation prevents.
Unless you intend to heat treat and polish, 416, while very nice to machine, is likely to not be your best choice for corrosion resistance, although unless you intend to subject your bike to chemicals, it's doubtful that any of the stainless grades would present a problem where corrosion is concerned. You are most likely to find 303S than any of the other free machining grades.
If you find you have to machine any of these materials, don't get caught up using a C5 or above carbide grade. C2 (Carboloy 883) is the best choice for stainless.
Hope this helps~
Harold
Reply to
Harold & Susan Vordos
304L is low-carbon and not usually considered free-machining. Low-carbon is the preferred alloy when you're going to be welding since it reduces the precipitation of carbides (or something similar)
303 (or the variants such as 303S) is free machining but don't expect to be able to weld it with much long-term success.
I regularly turn both of them on my little 10" lathe using HSS toolbits without any problems -- in fact, on a small lathe HSS cuts much better than carbide -- just make sure you keep the toolbit sharp.
To be honest, the only real difference I've noticed with 303, 304 and 316 is that the chips from 303 break far more easily (and are thus smaller) than those from 304/316. The actual force required to cut and the tendency to work-harden appear identical right across the 300 series alloys.
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Reply to
Bruce Simpson
From
Nor is 303 easily weldable.
If you expect them to remain rust free,
That goes for all stainless steels, if it is machined.
Stainless is known to lightly rust,
It's not actually the stainless steel that is rusting, it is the impurities that have been forced into a thin surface layer during machining. Passivation, which is really just a mild acid etch that will remove this layer.
Reply to
tomcas
Can an HSM type passivate stainless at home? How?
Karl
Reply to
Karl Townsend
Enjoyed all the replies but being a Junk Yard Dog, do you gentlemen have any
empirical analysis for determining the grade of S.S. you have acquired?--mainly because it was close to the finished size you wanted) Jerry
Bruce Simps> >
Reply to
jerry Wass
There's been considerable talk about passivating of late here on RCM, and the general opinion is that it can be done with citric or phosphoric acid. Again, from personal experience (I had to do one job myself, but my normal routine was to have all passivation done by the certified finisher I used to use) you can passivate at home, but it may be near impossible for the layman to buy the necessary chemicals if the process to (the old) MIL standards is followed. It may be that there are newer and acceptable procedures today, but I'm not familiar with them if they exist.
For the one time when I did my own passivation (to MIL specs) I had a fume hood at my disposal, so dealing with corrosive fumes wasn't a problem. Nitric acid (for 300 series stainless) and potassium dichromate is used, along with distilled water. It's been years since I did it and I do not recall the exact proportions, nor do I recall the exact temperature at which the parts must be treated, but it's well under boiling.
I am not familiar with other processes and have questions about how effective they may be. Passivation does nothing to the physical size of items so treated, so the only way you can tell if your work has been successful is if the items don't rust. Electropolishing is a different matter.
Harold
Reply to
Harold & Susan Vordos
My understanding is that the process removes any free iron from the surface, which might include unalloyed metals, too. Knowing how vigorously metals are stirred in induction furnaces, however, I can't imagine how there could be any free iron present. I'm inclined to think that the contamination comes more from contact with other metals. I've often seen linear scratches on bars of 303S that have rusted, but the material around the scratches is unaffected.
Harold
Reply to
Harold & Susan Vordos
Even so, a hot brew of nitric and potassium dicromate is not one of those things to cook up at home. And then, by another thread, how do you dispose of it once done?
Interestingly, the safety folks at work sent around a memo that potassium dichromate was one of the 'serious nasty chemicals' and they were going to be monitoring my 'use' of it closely. I turned in the jar that had been sitting on the shelf for years.
I'm not sure what about that in particular is so bad all of a sudden, but it was in a whole 'nother catagory from what I typically use.
Jim
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Reply to
jim rozen
316 is what you want for corrosion resistance, as it has a higher nickel content and they add Molybdenum. Unfortunately more desirable material properties don't usually coincide with machinability. It's not bad though. If you're only doing a few parts just take your time and use sharp tools. Usually you can find a material supplier that has a metallurgist on staff that will advise you as far as grades go. Good luck!
-- Bryce
Reply to
Bryce
Without some experience with each of them, cutting is likely to not tell you much unless you have 303S or Se. Each of them cuts differently from the other 300 series metals, all of which are non-magnetic. You can smell the selenium in Se when you cut it, but otherwise there's not much to go on. Based on odds, though, you're most likely to encounter 304, with 316 next most likely. Considering you have something that is near what you are looking for, I'd use it with no regard as to alloy. If it's non-magnetic, it has to be in the 300 series, and all of them will serve the purpose very well.
Sorry I can't provide more guidance.
Harold
Reply to
Harold & Susan Vordos

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