Exhaust bolts question

[limp]

Are these exhaust hanger bolts in the attached pic self tapping or do I need to run a tap through the hole I drilled in the frame for my dual exhaust hanger???
Thanks

 

[Bullitt347]

They are self tapping. If the bolt is 5/16" then the hole it is "self tapping" into should be around 1/4" maybe a tiny bit less.
The above is an example.
A 1/4" self tapping screw/bolt should have a pilot hole of 3/16" or slightly less.
So on and so forth.