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Discussion Starter #1
Quote Stainless kits do not cover critical items such as brake rotor and caliper, suspension, or frame components because stainless does not have the sheer strength for these applications. No matter how tempting the thought may be please DO NOT USE stainless on structural components...

This is an excerpt from a Texas-based retailer that sells stainless steel fastener kits for motorcycles. Are the OEM bolts used on our calipers, rotors, etc., not stainless? I know that there are different grades of stainless steel, so is this guy just using crappy-grade SS and doesn't want the liability, or is he right?

Thanks,

Pete
 

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Stainless has quite a bit of nickel in it and if the ratio of nickel to iron is high, then it is quite a bit weaker as a structural member than mild steel.  I think this guy is just covering his butt however, as graded bolts are graded on strength and hardness regardless of the material.  An SAE 8 stainless bolt would have the same minimum hardness and sheer strength as a same sized grade 8 steel bolt (or titanium or moly or whatever).

There is no AL in stainless steel BTW . . .

FYI:

 
TYPICAL CHEMICAL AND PHYSICAL PROPERTIES OF STAINLESS STEEL

304 430 410
Chemical Composition (Austenitic) (Ferritic) (Martenitic)
(Max. unless otherwise noted)    
       
Carbon 0.08 0.12 0.15
Maganese 2.00 1.00 1.00
Phosphorus 0.045 0.04 0.04
Sulfur 0.03 0.03 0.03
Silicon 1.00 1.00 1.00
Chromium 18.00
- 20.00 16.00
-18.00 11.5
-13.50
Nickel 8.00
-10.50  
   
Tensile Strength
 Ksi 84 75 70
 MPa 579 517 483

Yield Strength (0.2% offset)  
 Ksi 42 50 45
 MPa 290 345 310

Elongation (in 2' / 50.8 mm)
 % 55 25 25

Hardness (Rockwell)                
 B80   B85 B80

Modulus of Elasticity in Tension  
psi x 10 to the 6 28 29 29
 GPa 193 200 200

Modulus of Elasticity in Torsion  
psi x 10 to the 6 12.5    
 GPa 86.2  

Density
 lbs/cubic in 0.29 0.28 0.28
 kg/cubic meter 8060 7780 7780

Specific Heat          
          Btu/lb/F 0.12 0.11 0.11
32-212F ( 0-100C) J/kg.k 503 460 460

Thermal Conductivity    
 Btu/hr/ft/F      
 212F (100C) 9.4 15.1 14.4
 932F (500C) 12.4 15.2 16.6
 W/m.K  
 212F (100C) 0.113 0.182 0.174
 932F (500C) 0.149 0.183 0.201

Mean Coefficient of Thermal Expansion
x10 to -6/F 32-212F
(0-100C) 9.6 5.8 5.5
 32-600F
(0-315C) 9.9 6.1 6.3
 32-1000F
(0-538C) 10.2 6.3 6.4
 32-1200F
(0-648C) 10.4 6.6 6.5
 32-1800F
(0-982C)    6.9 .

x10 to -6/C               32-212F
(0-100C) 17.3 10.4 5.5
                                 32-600F
(0-315C) 17.9 11 6.3
                                 32-1000F
(0-538C) 18.4 11.4 6.4
                                 32-1200F
(0-648C) 18.8 11.9 6.5
                                 32-1800F
(0-982C)    12.4    

Melting Point        
 F 2550
- 2650
2600
- 2750 2700
- 2790
 C 1400
- 1455 1425
-1510 1485
- 1535
Electrical Resistivity
Microhm - mm Type 304 Type 430 Type 410 S13800
68F (20C) 720 600 570 1020
212F (100C) 780 675 640  
392F (200C) 860 770 720  
752F (400C) 1000 925 880  
1112F (600C) 1110 1050 1035  
1472F (800C) 1210 1150 1110  
1652F (900C) 1260    

For additional data please refer to the SSINA Handbook  
'Guidelines for the Selection and Use of Stainless Steel'
 

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Discussion Starter #7
abtech : An SAE 8 stainless bolt would have the same minimum hardness and sheer strength as a same sized grade 8 steel bolt (or titanium or moly or whatever).
That was just the kind of layman's explanation I was looking for. Thanks, Abtech!!!
 

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Pete : Quote (abtech @ Nov. 03 2003, 12:28pm)An SAE 8 stainless bolt would have the same minimum hardness and sheer strength as a same sized grade 8 steel bolt (or titanium or moly or whatever).
That was just the kind of layman's explanation I was looking for.  Thanks, Abtech!!!
a grade 8 bolt is marked. That was what you needed to know. an unmarked bolt is usually grade 5. Some SS bolts are only plated SS. Your source is probably using plated fasteners...
 

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Pete : Quote Stainless kits do not cover critical items such as brake rotor and caliper, suspension, or frame components because stainless does not have the sheer strength for these applications. No matter how tempting the thought may be please DO NOT USE stainless on structural components...
This is an excerpt from a Texas-based retailer that sells stainless steel fastener kits for motorcycles.  Are the OEM bolts used on our calipers, rotors, etc., not stainless?  I know that there are different grades of stainless steel, so is this guy just using crappy-grade SS and doesn't want the liability, or is he right?

Thanks,

Pete
He is correct in the sense that any commonly available SS fastener you find is going to have properties below that needed for the application....

The are going to be a 300 series part with a minimal tensile strength in the 75,000psi range.....
(By comparison, a Grade 5 fastener is rated around 120,000psi, a Grade 8 fastener is around 150,000psi, but most socket head cap screws exceed that spec, and are in the 180,000psi range)

That said, there are no Grade 8 stainless fasteners per se...

There are grades of SS such as 17-4PH & 410 etc, etc that have strengths in the realm of alloy fasteners, but its not something you will find on the shelf at the hardware store, and their other properties may not make them a good choice any way....

Bottom line:
His caveat is valid, unless you know the specs that are required and can choose a specialty SS fastener that meets them.
 

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Discussion Starter #12
BDA116 : Pete has sunk to a new low.
You should be banned for using that hideous beast for an avatar, you bastard!
 
It's tough stooping to your level, BDA, but I am capable.
 

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Discussion Starter #15
BDA116 : Quote (Pete @ Nov. 03 2003, 12:03pm)It's tough stopping to your level, BDA, but I am capable.
Stooping.
Louisiana Public School system at work.

They didn't teach us how to type while your wife is bitching you out over the telephone.
 

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I have several SS bolts with the SAE Grade 8 marking on them (The six lines on the hex cap). They can be ordered from several hundred fastener houses. I would imagine that SS bolts would conform to the ASTM A 354bd standard which specifies a material class of 'Steel Alloy Quench & Temper' which can include stainless. This spec is essentially identical to the SAE grade 8 and the 2 standards are used interchangeably and both utilize the same grade marking (as noted above).

And to answer an unasked question: No these are not stainless plated carbon alloy parts.
 

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abtech : I have several SS bolts with the SAE Grade 8 marking on them (The six lines on the hex cap).  They can be ordered from several hundred fastener houses.  I would imagine that SS bolts would conform to the ASTM A 354bd standard which specifies a material class of 'Steel Alloy Quench & Temper' which can include stainless.  This spec is essentially identical to the SAE grade 8 and the 2 standards are used interchangeably and both utilize the same grade marking (as noted above).

And to answer an unasked question:  No these are not stainless plated carbon alloy parts.
I would be interested in a link.....
 

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abtech : I have several SS bolts with the SAE Grade 8 marking on them (The six lines on the hex cap).  They can be ordered from several hundred fastener houses.  I would imagine that SS bolts would conform to the ASTM A 354bd standard which specifies a material class of 'Steel Alloy Quench & Temper' which can include stainless.  This spec is essentially identical to the SAE grade 8 and the 2 standards are used interchangeably and both utilize the same grade marking (as noted above).

And to answer an unasked question:  No these are not stainless plated carbon alloy parts.
I've seen SS with grade marks on them. Whats the application you use them on? I have several hundred in my garage...
 

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Stainless grade 8 & higher bolts

go through the materials section . . .

18.8 Stainless Steel - includes several alloys:
302: ASTM A276 Type 302; A167 Gr.2
XM7: 302HQ for cold heading screws
303: ASTM A582 Type 303; A320 Gr. B8F; A194 Gr. 8F
304: ASTM A193A Gr. B8; A320 Gr. B8; A194 Gr. 8
Contain approximately 18% chromium, 8% nickel, are non-magnetic and hardenable by cold working; a tensile strength range of 80-200,000 psi; good corrosion resistance. Used in food, drug and chemical equipment; bearing plates; heat exchanger tubes; pumps; valves.
 

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Isn't the problem something to do with electro-chemical corrosion between aluminium and stainless steel?

Need to check this out but i'm assuming it's because of the very high chromium and nickel conten. Much worse forAl/ss than Al/ms although in theory it's bad in both instances. I think.

Don't use stainless steel bolts for your engine /slider mounts.

Years ago I used to work in a fighting vehicle assembly shop, Scorpion and Scimitar light tanks for those that are familiar with the beasts. Heat treated armoured aloominum alloy welded hulls. Corrosion was a serious problem.i seem to recall  secial paste was used in bolt holes to protect the alum. Twas a long time ago............  
 
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