Why A/E crank shaft is drilled for lubrication but not in M/E ?

•  It will reduce the strength of the crankshaft.
• May possible to occur crack or failure
• So we drill the hole in a/e Engines.
• For main engine we use semi build crank shaft .- web and crank pin both are single oice 
• For a/e engine we use forged crank shaft- its fully moulded type.good fatigue strength.