a9cc56f1____Group_15___2012___GICL_Wiki__3
[0] Blade Nut [1] 1 [2] 1 [4] Steel [5] Durability and strength. [6] Stamped out [7] Cheap and cost effective [3] 
Passes through the lower blade guard, blade and upper blade guard. It acts as the central pivoting/connection point and is vital to the operation of the saw. Failure here is unacceptable.
Gate 3 - Group 15 - 2012 - GICL Wiki