<VV> Bolt Grades

[John Kepler]

>

I have not done any comparative testing of bolts, but what I understand 
is that while Grade 8 (and higher) bolts do have a higher tensile 
strength, they are overall more brittle than Grade 5 bolts, and are not 
perhaps the de facto 'best choice' for some applications, especially 
those taking a lot of high shock loads and abrasive wear. 

Absolutely incorrect!  Grade 8's are LESS brittle than Grade 5's based on
the fact that they are alloy steel rather than Low-Carbon steel.  And the
numbers are:

SAE Grade 5:  1/4-1"
  Proof Strength:  85,000 PSI
  Tensile Strength:  120,000 PSI
  Material:  Low-Carbon Steel, Quenched & Tempered

SAE Grade 8:  1/4-1"
  Proof Strength:  120,000 PSI
  Tensile Strength:  150,000 PSI
  Material:  Medium-Carbon Alloy (Mb) Steel, Quenched & Tempered