Technical Stainless steel fasteners!

Guys, we were having a discussion about why stainless steel bolts have a tendency to galled when using stainless steel nuts! You can use SS bolts on about anything with no problem, but when you go SS on SS, galleding occurs regularly.
One guy produced an article stating it was because SS is soft! In writing! It has been my experience that SS is extremely hard! Both when I used to machine it in the previous century and when I worked it by hand! You find out how hard it is!
Then a Brinell hardness chart/was produced and it showed SS twice as hard as regular steel.
I know there’s a ton of knowledge here and probably you guys use a lot if SS , because it’s shinny!


Any ideas on this? Thanks in advance…


And yes, I cannot spell Gauld , goll, gall, or what ever it is, and spell check is no help!





Bones

 

Friction and heat

 

Bones (et al) -

NOT ALL...stainless steel is...hard !!
Many if not most, hardware store S.S. fasteners are actually a softer grade stainless steel.
You'll pay "extra", for quality grade stainless fasteners.

Also, don't cheap out, a little "Anti-Seize" goes a long way an ANY stainless fastener joint. Be the nut, or "other end" being any other ferrous material, would do well with a touch of Anti-Seize.
Corrosion (rust), will also help cause stainless fasteners to want to gall.

And as for friction AND heat...again, not so much.
The "friction"...causes...the "heat". Otherwise known as...welding !

Mike

 

Galled

T-304 also referred to as 18-8 are generally considered to be slightly stronger than grade 2 carbon steel fasteners. As far as hardness goes, they are softer than the carbon steel equivalents. T-316

Hard to machine because they tend to was up and gall. This is especially true with stainless nuts as both nut and bolt 'mush'. If you think of a carbon steel nut as a low quality die, it can force the stainless to conform to it's shape. Anti-seize helps in either case to limit galling.

From Marine Bolt Supply
As you can see, the main difference between T304 and T316 is corrosion resistance, not hardness, tensile strength or yield strength.


Stainless Information
Type 304 / 18-8 Stainless:
304 grade is the most common form of stainless steel used around the world. It contains between 16 and 24 percent chromium and up to 35 percent nickel—as well as small amounts of carbon and manganese. The most common form of 304 stainless steel is 18-8, or 18/8, stainless steel, which contains 18 percent chromium and 8 percent nickel.
304 stainless steel has a high resistance to rust. It withstands corrosion from most oxidizing acids and is often used for kitchen and food applications. However, it is susceptible to corrosion from chloride solutions (notably saline environments with high amounts of sodium chloride). Chloride ions can create localized areas of corrosion, called "pitting," which can spread beneath protective chromium barriers to compromise internal structures. Solutions with as little as 25 ppm of sodium chloride can begin to have a corrosive effect.


Stainless Type Tensile Strength Yield Approx. Hardness
Type 18-8 / 304
80,000 - 150,000 (standard range)
Diameters 1/4" to 5/8" 100,000 to 125,000
Diameters 3/4" to 1" 100,000
Over 1" 80,000 to 90,000


80,000 to 90,000 (Diameters 1/4 to 5/8)
45,000 to 70,000 (Diameters 3/4 and over)

B85-95

Type 316 (Marine Grade) Stainless:
316 grade is the second-most common form of stainless steel. It has almost the same physical and mechanical properties as 304 stainless steel and contains a similar material make-up. The difference is that 316 stainless steel incorporates about 2 to 3 percent molybdenum, which increases corrosion resistance—particularly against chlorides and other industrial solvents. Alternative 300-series grades can contain up to 7 percent molybdenum.

316 stainless steel is commonly used in many industrial applications involving processing chemicals, as well as high-saline environments such as coastal regions and outdoor areas where de-icing salts are common. Due to its non-reactive qualities, 316 stainless steel is also used in the manufacture of medical surgical instruments.

Stainless Type Tensile Strength Yield Approx. Hardness
Type 316
85,000 - 140,000 (standard range)
Diameters 1/4" to 5/8" 120,000
Diameters 3/4" to 1" 95,000
Over 1" 80,000

80,000 to 90,000 (Diameters 1/4 to 5/8)
50,000 to 70,000 (Diameters 3/4 and over)

 

I just buy what ever Fastenal has on the counter, nothing special, I would imagine, but probably not cheap stuff, either.
That is the bolts I had a few problems with. Not really searching for a solution , just wondering “ WHY” it happens, even with a little lube! Doesn’t happen with mild steel on mild steel, or SS bolts on mild steel, or aluminum, just with SS on SS.

As being “soft” , I have used br*** bolts and nuts before and have not encountered any problems.


Bones

 

And.......not all stainless is rustproof.

 

When stainless pistols first came out , they had bad galling problems. Since then the changed the type of stainless. Still need a good lube . On automotive stuff , valves are magnetic and can rust . Forgot what i was going to say about other stainless. Oh well , just say stainless slow . Stain less .
I just installed a stainless AC compressor mount . It came with unmarked stainless, I used good old , repeat , old USA made grade 5 carbon steel . Better safe than sorry . Oh , I use the copper anti seize . Never any problems.

 

That's a fact, and when you're welding stainless in a boiler, if you beat on it with a carbon steel hammer or grind it with a wheel that has been used on carbon steel, it's going to rust. As for its strength or ease of cutting, stainless is soft.

 

Gall. -- verb (used with object) to vex or irritate greatly: His arrogant manner galls me. to make sore by rubbing; chafe severely: The saddle galled the horse's back.

Galling stainless hardware irritates me, too! I don't use it unless there's a very good reason.

And if I have to use a bolt and nut, it gets antisieze.

 

Hardened materials tend to gall less than more malleable materials. The main thing that causes galling is the metals crystal structure. Some crystal structures allow layers of the material to slip off more readily, making them prone to galling. Stainless is often face-centred cubic, which galls more than other crustal structures.

(my High School industrial arts teacher, Mr Hobbs, wherever he is, probably just smiled that I actually remembered something from 35 years ago).

Cheers,
Harv

 

Correct.
AND, some stainless is magnetic.

Mike

 

Just an interesting tidbit of information regarding Swagelok fluid fittings. They make br*** and stainless steel fittings. The fittings are silver plated to resist galling, as many applications can not have any contaminants. Other brands are not.

How does this apply to the subject? Maybe someone will start plating stainless nuts and bolts for anti-galling purposes.

 

I worked with a little stainless as a machinist but forgot the details.

Some information about stainless steel.
Here:
https://www.google.com/search?q=aus...msung-nf-rev1&sourceid=chrome-mobile&ie=UTF-8

Here:
https://www.google.com/search?q=mar...AYRkgcDNC45oAf1fw&sclient=mobile-gws-wiz-serp

Here:
https://www.google.com/search?q=fer...v=717f11d1955b1b6b&sca_upv=1&sxsrf=ADLYWIKxP-
H5Cf3Qkx32WAT8LtNLck9qpA%3A1717627487453&ei=X-pgZoejG6aH0PEPxt3M6QQ&oq=ferriti+stainless+steel&gs_lp=EhNtb2JpbGUtZ3dzLXdpei1zZXJwIhdmZXJyaXRpIHN0YWlubGVzcyBzdGVlbCoCCAAyBhAAGAcYHjIGEAAYBxgeMgYQABgHGB4yBhAAGAcYHjIGEAAYBxgeMgYQABgHGB4yBhAAGAcYHjIGEAAYBxgeSL2GAVCDLVjXT3AAeAKQAQCYAYcBoAHrC6oBBDE1LjO4AQHIAQD4AQGYAgqgAuAIwgIEEAAYR8ICDRAAGIAEGLEDGEMYigXCAgoQABiABBhDGIoFwgIOELkBGIAEGEMYigUY7wTCAgcQABiABBgNmAMA4gMFEgExIECIBgGQBgiSBwMyLjigB4dy&sclient=mobile-gws-wiz-serp

 

I stay away from stainless except for maybe bright work trim or interior stuff

 

I love stainless steel, I use 304 if it will be polished, 303 if I'm machining something that isn't structural.

 

The best explanation I've heard is this...

'Stainless steel has a lot of chromium in it. When the chromium makes contact with oxygen in the air it oxidizes (rusts). The difference between iron oxide (red rust) and chromium oxide is that chromium oxide is impervious to air and water. This is why stainless is stainless, it seals itself. You would not expect great results in attempting to screw together a rusty bolt and nut. The other problem is that chromium oxide readily bonds to itself, furnishing the 'glue' that seizes it.'

Any SS to SS joint, you better use anti-seize. I've seen nuts turned onto a bolt by hand, not even tightened against anything, and seize when you'd try to remove them. And if you're not using it on SS to aluminum, you're living dangerously. Particularly if exposed to any moisture. AMHIK... Anymore, ANY stainless fastener I use gets anti-seize no matter what it's threaded into.

I also know from experience that SS is harder to machine. The higher the strength, the harder it is to work. 18-8 is the 'compromise' type most commonly used for fasteners.

 

From my sheet metal working days
Stainless steel came in different hardness
1/4, 1/2, and 3/4 hard
3/4 hard is harder than wedding ****

 

what gall to misspell gall....yall....

 

Amen.


... and any time I use anti-sieze, I end up looking like the Tinman from the Wizard of Oz.

Cheers,
Harv

 

Nut's and Bolt's yes.....I don't weld it/bend it/drill it...... It's for cosmetics. NEVER had a piece rust, but my **** is inside/no rain, etc......and.......anti seize, or a lil grease on threads never hurts.......YRMV...........

 

I never had a problem working with 316 stainless at power plants near the coast for over 40 years. We used different grades of anti-seize and found Silver Goop was the best and most expensive.

 

ALWAYS USE ANTISIEZE ON ANY STAINLESS JOINT!!!!! If it weren't so pretty, I wouldn't use it anywhere. It is just nasty to work. I put 2" x 7" stainless C-channel sheet metal facade over a 2x4 rectangular steel tubing frame on my Mysterion reproduction. Here is an excerpt from my book on the Mysterion;

"I bought a bi-metal 4¼” hole saw and after I laid out the hole pattern, proceeded to start cutting the holes on my drill press. Now a note on how I drill. On drilling steel I rarely use cutting fluid. Unless the part is ½” thick I normally just shove the bit through the part. If it seems dull I go to the bench grinder and sharpen the tip and keep shoving. Works great on steel and my $9 Chinese 29 piece drill bit set has lasted at least 10 years. I have had to replace all the bits below ¼” several times but that is because they break, not particularly because of my bad shop practices. Anyway, I started shoving the hole saw through the thin stainless and the saw started squealing and smoking within a few seconds. Relying on my vast drilling experience I just shoved harder and the bit squealed louder and started turning red. That was a pretty good clue to stop so I did. I looked at the bit and the teeth were totally burned off the tool. I did the math; $24/hole saw, times ½ a hole, times 24 holes. I had to come up with plan B. I did some reading on stainless steel and it is pretty nasty stuff when it comes to machinability. There are various engineering charts of relatively machinability of metals comparing all types of alloys to a standard AISI 1212 carbon steel at 100%. It seems our beloved stainless steel alloys fall in a 35% to 40% for the most common alloys (313, 302) which is pretty bad."

"Here are some of its really bad characteristics;
· It work hardens. This means when you start cutting/drilling/turning stainless the surface turns very hard and resists further machining.
· It has a very low thermal conductivity compared to other metals. Any heat generated by the cutting tool stays at the cutting tool and overheats it quickly.
· It is ‘sticky’ and loves to adhere to itself and other metals, welding itself in place.
I bought another hole saw and decided to experiment. I tried some of the common cutting fluids but none worked very well. It became clear that localized heat buildup was the biggest problem I was having. I decided to try just flooding the bit with plain water and that was the answer! Water has the highest specific heat of any compound so is the perfect cooling medium and has enough lubricity to prevent seizing. I started knocking out holes and finished both rails with the same bit that is just as sharp as when I started. Now I was able to drill all the various other holes needed in the facades with no problems."

 

wow-nice tip!~!

 

There's a tech week winner right there!

 

Do I win a free Harbor Freight 3/4", 25' tape measure? I'm down to 12 or so so need another couple.

 

That's the key.
Also the coolant they use at work is cut with water......goes in all machines (saws, lathes, mills...). Coolant, slower speed works for stainless and a shallower cut saves the bits.

 

Gaul durn stainless

 

SAE 300 series SS is non magnetic and non hardening SAE 400 series SS is magnetic and can be hardened. I’m not sure where a person can purchase silver plated fasteners but when I worked on gas turbines many of the fasteners were silver plated, ***anium will gall also, likewise aluminum threaded joints can also gall, anti seize if your friend. I’ve had luck using milk of magnesia on SS fasteners that are subjected to high temperatures.
Dan

 

I think I heard somewhere that SS bolts are less hard or break more easily than regular bolts. This sounded odd to me... Any truth, actual factual truth, that is.

 

There are lots of grades of stainless, the same as there are lots of grades of mild steels. Each of them can be heat treated, work hardened or surface finished differently too. This oleads to lots of variation in:

a) tensile strength (how much you can stretch a bolt before it goes kablooie).
b) shear strength (how much side loading you can put on a bolt before it goes kablooie).
c) hardness (how much you can lean on the bolt surface before it smooshes).
d) yield strength (how much energy you need to put into a bolt before it permanently bends instead of springing back).
e) toughness (how much energy you need to put into a bolt, even if it is deforming, before it finally lets go).

Cheers,
Harv