[QUOTE=sandy stone;3620388]I don't know if I can prove you wrong, but maybe convince you?
The people who manufacture threaded fasteners have gone to some trouble to determine what is needed for a secure, long-lived joint. Their intent is that a bolt will fail in tension before the threads strip out. After some decades of testing and experience, they determined that with steel
, a thread engagement depth
of 1 to 1-1/2 times the diameter of the bolt is sufficient. /QUOTE]
Ideally in cast iron it should be around 2.5 times the diameter of the fastener.