Originally Posted by moparx
i can appreciate full thread engagement, but bottoming the bolt is worse than having a few threads short. if you have a thread or two more engagement than the bolt diameter, that is all it needs.
beer

Here is a rule of thumb that you cant go wrong with
1 X thread diameter in steel
1.5 X thread diameter in cast, bronze etc.
2 X thread diameter in aluminum
Any more than that is of little gain (fastener will usually break first) any less and dramatically reduces strength and threads will pull.

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