How hard is "annealed" 304 stainless?

I'm going to turn some simple objects from small sections of annealed

304 stainless steel.

How soft is that compared to stainless items I'm familiar with like kitchen utensils or stainless nuts and bolts?

If I want to use it in the kitchen when I'm done, will I need to harden it to avoid having the surface easily marred? What's the best way to harden it?

Reply to
Ben Jackson
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It's going to be somewhat softer. 304 can be hardened only by cold-work. A stamped kitchen utensil picks up some hardness in stamping -- sometimes, quite a lot. Cold-headed bolts are going to be harder than annealed 304.

There is no thermal treatment that will harden it. What you get is what you get. If it was a structural part you could have it shot-peened, which would harden the skin. But I doubt if that's practical for what you're doing.

If you need a stainless that you can harden with thermal treatment, you need one of the 400-series SS with some significant carbon (420 or above; you need less carbon than you do for plain carbon steel, because the chromium increases the hardening potential of the carbon that *is* in there), or a precipitation-hardening grade. Unless you really need hardness, it isn't worth it.

Here's a thorough list of the properties of 304:

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Good luck with your project.

-- Ed Huntress

Reply to
Ed Huntress

That goes for all 300 series (austenetic) stainless steels.

Reply to
tomcas

Thanks. Having worked with copper in various hardnesses I wasn't sure if annealed 304 was going to be almost butter soft like annealed copper and require hardening before it could be used.

Reply to
Ben Jackson

It's not that bad, but it's pretty gummy. If you've machined copper, though, you know what that's all about.

-- Ed Huntress

Reply to
Ed Huntress

However, the real issue with 304 is not hardness, but toughness. It is tough to machine, kinda like pure copper. It work hardens and wears tools fast. And it also likes to stick to the cutting tool edge. So enough tool pressure must be used to get a constant chip. If drilling stops producing a chip the 304 will harden at the point of contact and then dull the drill. Use plenty of cutting oil or coolant, slow enough speeds, and enough tool pressure to get a constant chip. And don't dwell with the cutting tool. It either must be cutting or it must be removed from the work. ERS

Reply to
Eric R Snow

The worst is if you are counting on something being 303. Last week, I had eight parts ganged up on my miller. I work with 303 because even though I pay 30-40% more for bar stock, I can run it twice as as fast. So I am running along, happy, with a 6-flute roughing mill, the power feed going and a coolant flood, and guess what- The supply place (Nameless here but very well-known) must have been a little short filling my order for precut stock..maybe went to the dropoff shelf. Long story short, hit one of the pieces that was

*316*, and had what amounted to a train wreck/smashup. Out $56.00 for the end mill, had to retram the table, but saved the parts. Post-crash showed two parts out of 8 were that f*cking 316. I discussed it with them when I calmed down. (Interstate death threats are prosecuted, so I waited two days...) To their credit they did freak out over it, went to the division that shipped it and "interviewed" the guy who filled the order, offered me a credit, etc., called the house about 40 minutes after I sent the e-mail.

But I only THOUGHT I hated T316 before this.

Reply to
Grunty Grogan

I worked in a machine shop with an associated foundry. If anybody ever found out exactly how this happened they didn't tell, but a bucket or two of ball bearings were dumped into the melt at some point such that they didn't melt.....

Nothing like spending two days machining on a large casting and hitting what looked liked grapes..... it isn't fun trying to run from what was left of a 1.5 inch diameter end mill that was 8 inches long, either....

For the next several weeks, an eruption of cussing and brisk activity was most likely caused by hitting one of those little joys....

Reply to
Gene Kearns

We hit a HSS tap once, right in the middle of a block of steel. I forget what the grade was. We sent it back to the service center and suggested they wrap it around their necks.

-- Ed Huntress

Reply to
Ed Huntress

I had heard on someone hitting a FILE in an iron casting. Old machinist told me about it. I thought it had happened decades before, but the way he was animated, it could have happened that morning. People STAY pissed off about those things. In retrospect, my discussion with the metal supplier was a LOT like the phone call from the President to the Premier in "Doctor Strangelove"! "This is a FRIENDLY CALL! If it were not, we would not be having it". (You'd get nuked/ You'd be getting a summons..)

Reply to
Grunty Grogan

I'll say. It was 30 years ago and I'm still pissed. It wasn't really as bad as it could have been, though, because the block was being roughed with a ratty old endmill that I would have scrapped anyway, if it were me. We did have to show it to the customer to explain why the job was late, which is the reason I'm still pissed.

Or his precious bodily fluids would be leaking out...

-- Ed Huntress

Reply to
Ed Huntress

I worked at a place where we would get castings from a customer who was buying the cheapest iron for the pours. We found ball bearings, races, and taps in these castings. We refused to do anymore until they used better mnaterial. The material improved for a while then we started getting hard spots again. Not taps etc., but just big amorphous spots and lines of extra hard material. The castings looked allright but some had spots on the outside that were slightly raised and just a little different in color. After machining these spots the color was very different. I told my boss that these castings must have been weld repaired because of porosity. He didn't think so because the surface of the castings had a uniform sand cast finish. But when he asked the customer they admitted that they were welding up the shitty castings and blasting them with steel shot after welding and grinding to hide the welds. ERS

Reply to
Eric R Snow

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