Hey guys,
Im going to be drilling and tapping my front cover for a turbo oil return and have decided to use a 1/2 npt fitting, however which drill size is best. Has anyone ever drilled with a 3/4 bit. This is very close to the same size as the tap but was just wondering what size others have used before i go drilling away.
Thanks

 

yes, that's exactly what i did. works beautifully

 

1/2"x14 NPT tap requires a 45/64 ths bit. Good luck on finding one at a reasonable price. I drilled mine with with more a common, easy to find, 11/16 ths bit. Works fine, that 1/64 is not a problem when tapping into aluminum. A 3/4" bit may be pushing it if you want a good seal.

 

I dropped mine off at a machine shop and they drilled and tapped for 30.00. Using a 1/2" NPT to -10 A/N fitting.

 

Google is a wonderful thing:

http://www.newmantools.com/tapdrill.htm

Rich