ABOUT BOLTS : MARKING

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A bolt is a bolt. Is that completely true? There are so many kinds of bolts and so many standards, sometimes is difficult to choose the right one. What standard, what diameter, what pitch, what material to choose ? There is huge documentation you can find, here is just a very short guide to help making a choice.

  METRIC BOLTS  IDENTIFICATION            INCHES BOLTS IDENTIFICATION 
 MARKING               Proof strength  (Mpa)  Tensile strength (Mpa)  MARKING Proof strength   (psi)  Tensile strength (psi) 
 4.6   225   400   grade2  55,000   60,000 
 4.8  310   420   grade5  85,000   105,000 
 5.8  380   520   grade8  120,000   150,000 
 8.8  580   830   18-8    100,000 
 9.8  650   900       
 10.9  940   1040       
 12.9  970   1220       
 A2    700       
 bolts1   

How to calculate necessary bolt diameter:

d1= (4βP / πσt)1/2   

where: 

P – longitudinal force necessary to tight

β = 1.25  -  1.35 – torque coefficient

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