Stainless question .

RBHarter

West Central AR
I have a project that calls for .120 SS . I need to be able bend it and tap it . Rustless is important . I can't remember now ........ I should have written more down when Dad talked about SS . 304 , 404 , 440 ? 440 is more a cutting tool isn't it ? The nonmagnetic aspect isn't important for this as much as the rustless aspect . I have to bend it and have it hold 90° and take and 8-32 or more likely an 8-40 .
I could make the first model from something else but the long term survival of the tool the SS will give as well as rub friction .
 

Pistolero

Well-Known Member
120SS?????
300 series are nonmagnetic, pretty rust resistant. Can be drilled, cut, etc. but needs sharp tools
and care to NEVER let a dull tool slide over a surface rather than cut, it will harden the surface to
the point you will literally not believe how you pretty much cannot cut it now.

400 series are magnetic, heat treatable and less corrosion resistant but still pretty good.

I have never heard of 120, will look it up.

Bill
 

Pistolero

Well-Known Member
OK, missed the "." entirely. The basic alloy info is there. If you need hard, 400 --
if you must maximize corrosion resistance, 300 series....which is pretty much unweldable
due to stress corrosion cracking issues after welding unless you use 321 or 347 which have
special carbon scavengers added to make them weldable. You should be able to thread
300 series, but I have not tried it personally. Not actually terribly hard to machine with
good sharp tools.

300 alloys work harden tremendously. I have never tried bending them much but they will
get much harder with deformation. But the 300s are better for corrosion in severe environments
like salt water. Rubbing......you CAN get into issues with some alloys rubbing on like alloy, get
some galling.

Sounds to me like 304 would be good. 301, 302, 303 are almost exactly the same, too.

Hope this helps.

Bill
 
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Bret4207

At the casting bench in the sky. RIP Bret.
Just a thought based on several people I've dealt with thinking that stainless means no rust. Stainless, at least any I've ever dealt with, isn't "rust proof" any more than the Titanic was unsinkable. Depending on what you're making, if you absolutely need "rust proof", then another material might be better. Bronze, brass, aluminum, galvanized. There is a commercial galvanized sheeting a local roofing company uses that looks like stainless, bends in a brake and holds it's shape beautifully and stands up as a manure gutter cleaner chute for years and years without even a sign of rust. The stuff I ended up with is just about .120 or a little heavier. Might be worth looking at. Of course if it's food grade or something, then all this is worthless info!
 

RBHarter

West Central AR
Nope not food grade .
The design plan called out SS .
304 is kind of what I was thinking but I wasn't sure . I remember there being some that when polished were hard surface and pretty much rust free with any sort of care but would rust in a hurry if scarred .

Sorry to be vague about the use , but ........ potentially there might be a value in the tool , knowing my luck it'll be another novelty gadget best served by giving away as many as would ever sell .

The wear is limited to a single low load pivot point . The abrasion would be a rub load of much softer metal at very low speed and impact .

Food for thought .
Yes 120/1000 inch thickness . Probably less costly if called 1/8 in as that is likely held to a +-.005 vs +-.0005 .
 

KeithB

Resident Half Fast Machinist
We use a lot of 304 but it is in rods or bars and not thin strip stock. It is widely available but can you get it in 12 gauge? There may be a similar but slightly different grade of SS that is designed for sheet/strip stock use where bending and forming is required. It is probably what I would try first.

The accepted definition of a Stainless Steel alloy is one "that has 10.5% Cr or greater and shows passivation in an oxidizing environment". When exposed to other chemicals besides oxygen it may react in various ways including staining or discoloration.

Edit to add: Using a carbon steel wire brush or having heavy rubbing (contact) forces with carbon steel parts can leave Fe ions on the surface of the SS which will rust. We learned to only use SS wire brushes on SS parts because of this very outcome.
 
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JonB

Halcyon member
I wish I could remember what SS sheetmetal my former employer used. They used lots of 10 GA and 12 GA. Bent/formed into boxes and welded (electrical enclosures in food processing plants).
Adding to what Keith mentioned about carbon steel wire wheels...Another Big no-no is "cross over" use of sanding/grinding/polishing abrasive discs...meaning don't grind on SS with discs previously used on carbon steel.
 

KeithB

Resident Half Fast Machinist
JonB, yep, we try to keep the tools we use on stainless, carbon steel, and aluminum separate to prevent that very issue.
 

Ian

Notorious member
Whatever is used to make commercial kitchen counters/sinks/tables might be what you need.
 

smokeywolf

Well-Known Member
My first thought was 316L. Same as 316, just lower carbon content. Excellent corrosion resistance, takes a little tighter bend than 316 and maintains its corrosion resistance around any welds.
 

KeithB

Resident Half Fast Machinist
The L added to a SS grade also means it is weldable for the reason Smokey stated.
 

Bret4207

At the casting bench in the sky. RIP Bret.
When I was in Okinawa a local brewery had some new stainless tanks erected. The worker wire brushed the welded seams with carbon wire wheels. Oooops! Then the brewery got a chance to tear down the new/old tanks and put up brand new ones brushed with stainless!
 

Pistolero

Well-Known Member
Actually, if you do accidentally contaminate SS with carbon steel, a wash with a reasonably strong citric
acid solution (Lemishine) will remove the carbon steel and repassivate the SS. Good tip to keep
handy.

If the rubbing load is on a pivot on a shaft, a bronze bushing may be the answer to any galling
problems that may come up.

Bill
 

Ian

Notorious member
Lemishine solution is also great for removing rust spots from Ruger 10-22 factory barrels. Redox and passivation at work.