Fastener Grade & Material Strength Comparison (With Plating)

Fastener Strength

Bolts, Screws (Externally Threaded)
US (SAE)
Metric (ISO)
Proof Load
Tensile Strength
Yield Strength (1)
Comments (2)
Grade
Property Class
ksi
MPa
ksi
MPa
ksi
MPa
 
4.6
33
225
58
400
35
240
 Carbon Steel, Applicable Sizes M5 - M36
1
  
33
228
60
414
36
248
 Carbon Steel, Applicable Sizes 1/4" - 1-1/2"
2
  
33
228
60
414
36
248
 Carbon Steel, Applicable Sizes Over 3/4" - 1-1/2"
 
4.8
45
310
61
420
49
340
 Carbon Steel, Applicable Sizes M1.6 - M16
 
AX-50 (4)
    
73
500
30
210
 Stainless Steel, Applicable Sizes ≤ M39, (4)
2
  
55
379
74
510
57
393
 Carbon Steel, Applicable Sizes 1/4" - 3/4"
 
5.8
55
380
75
520
61
420
 Carbon Steel, Applicable Sizes M5 - M24
 
AX-70 (4)
    
102
700
65
450
 Stainless Steel, Applicable Sizes ≤ M24, (4)
5
  
74
510
105
724
81
558
 Carbon Steel, Applicable Sizes Over 1" - 1-1/2"
4
  
65
448
115
793
100
689
 Carbon Steel, Applicable Sizes 1/4" - 1-1/2"
 
AX-80 (4)
    
116
800
87
600
 Stainless Steel, Applicable Sizes ≤ M24, (4)
5
  
85
586
120
827
92
634
 Carbon Steel, Applicable Sizes 1/4" - 1"
 
8.8
87
600
120
830
96
660
 Carbon Steel, Applicable Sizes M5 - M36
 
9.8
94
650
131
900
104
720
 Carbon Steel, Applicable Sizes M5 - M36
8
  
120
827
150
1034
130
896
 Carbon Steel, Applicable Sizes 1/4" - 1-1/2"
 
10.9
120
830
151
1040
136
940
 Carbon Steel, Applicable Sizes M5 - M36
 
12.9
141
970
177
1220
160
1100
 High Strength Carbon Steel


Note 1: Yield strength is stress at which a permanent set of 0.2% of gage length occurs.
Note 2: Values for sizes other than those specifically listed may be obtained from Proof Load tables for each specific size.
Note 3: Strength data for carbon steel fasteners based upon SAE table J429 (US) and J1199 (Metric)
Note 4: Stainless Steel:
 
ISO
AISI
 Type
 
A1
303
 Austenitic, Free Machining, Cold Worked
 
A2
304
 Austenitic, Corrosion Resistant, Cold Worked
 
A4
316
 Austenitic, Corrosion & Acid Resistant, Cold Worked
 
SX
400 Series
 Martensitic, Spring Stainless Steel, Heat Treatable

Plating & Treatment of Fasteners

For corrosion resistant applications, all steel fasteners should be zinc plated with the highest protective service condition available per thread configuration.  Stainless steel fasteners should be passivated.

Steel fasteners used for interior or cosmetic applications should be chrome plated per ASTM B 456, class SC-3.

If stripping and re-plating of fasteners is required to meet the aforementioned criteria, documentation must be made available to verify that all applicable post plating treatments and standards have been met.  Batch testing of stripped and re-plated fasteners is required to ensure there is no hydrogen embrittlement.

US Standard: After manufacturing, steel fasteners should be electroplated, zinc with a yellow chromate conversion per ASTM B633, Type II - Yellow (please refer to table for thickness). 

Metric: After manufacturing, steel fasteners should be electroplated, zinc with a yellow chromate conversion per ISO 4042, (please refer to table for thickness).

Plating Thickness for Steel Fasteners, Zinc, Yellow Chromate Conversion
Bolt size
Metric DIN 267
US ASTM B633
Thickness (Micro meter / inch)
Dia, up to #8 (M3)
A1L
-
3µm / .00012"
Dia. >#8 (M3) to 5/16" (M8)
A2C or A2L
SC1
5µm / .00020"
Dia. >5/16" (M8) to 7/8" (M22)
A3C
SC2
8µm / .00031"
Dia. >7/8" (M22) to 1-1/8" (M33)
A4C
SC3
13µm / .00051"
Dia. >1-1/8" (M33) and greater
A5C
-
15µm / .00059"

Hydrogen Embrittlement

Fasteners or fastener components with hardness greater than or equal to 320 HV (32 HRC) are susceptible to hydrogen embrittlement when these parts are pickled and/or electroplated.  This may cause these fasteners to fail at relatively low loads even if stress relief annealing (baking) is performed after plating.  Examples of hardened fasteners are steel bolts - US Grade 8 (Metric property class 10.9), hardened steel washers, spring washers, etc.  These types of fasteners should be mechanically plated to avoid hydrogen embrittlement.

A suggested Standard for mechanical plating is ASTM B695-00 Standard Specification for Coatings of Zinc Mechanically Deposited on Iron and Steel - using similar plating thickness as discussed in the above table.

All safety-related, high strength fasteners that are plated or chemically cleaned should be provided with certifications showing freedom from hydrogen embrittlement, based on a representative sample of the actual production fasteners, tested for hydrogen embrittlement by the OEM Contractor or a supplier following ASTM F519 procedures.  An ASTM F606 wedge-test sample may be used in place of the F519 standard samples.  Test loads should be a minimum of eighty (80) percent of yield strength or proof load and held for a minimum of 168 hours.  Any failures would be cause to reject the entire lot.