#1 Main Bearing oil hole offset, open up ?

I've done them to 3/8" on a few motors if I can get the bit started. when it won't start for what ever reason I just go to 5/16" on all of them. the 1/4" hole for #1 is just fine. when using a drill bit it's a good idea to insert a long bit into the main gallery so the bit doesn't get stuck or break off. open up and camfer the bear hole also and make sure the back of the bearing doesn't have a raised ridge, if so file it down.