Introduction and classification
A bolt is a long metallic piece that has a round stem as its body. The body is threaded in a helical (circular) manner. The metallic piece is topped with a head on one end that allows it to be turned, either into the object or the nut.
Bolts used in steel structures are of three types:
1) Black Bolts
2) Turned and Fitted Bolts and
3) High Strength Friction Grip Bolts
What is the difference between 4.6 and 8.8 bolts
Bolt Grade :- Two grades of bolt are commonly used. These are grade 4.6 and 8.8. The first digit relates to the ultimate strength of the material, whilst the second is the ratio of yield stress to ultimate strength. Thus grade 4.6 bolts have an ultimate material strength of 400N/mm2 .Simlarly grade 8.8 bolts have an ultimate strength of 800 N/mm2 and a ratio of yield/proof stress to ultimate strength of 80%. Simple grade 4.6 bolts without corrosion protection are commonly called blackbolts.