1/8"NPT Drill Size?

[WhiteTsiAwd]

Tapping my manifold for a EGT probe and I'm trying to figure out what size drill bit I will need for my 1/8"NPT fitting to fit in?

Thanks,
Cody

 

[hottboost]

You have to drill the hole first and then tap it. I.e., drill with a 5/32", then 11/32", then use the 1/8-27-NPT tap. Hope that helps. Let me know how it turns out

 

[halik008]

.277 or .227 ...can't remember which of the two

 

[DSM90AWD]

Home Depot/Sears/Most Chain Auto stores carry this tap and it says right on the package what drill bit you'll need (some even come as a set)
Mine was 21/64"

 

[steve]

IIRC, it's a R drill (0.339") for tapping 1/8"-27 NPT.
The next bigger common size is 11/32" (0.34375")

Steve

 

[WhiteTsiAwd]

Alright thanks guys, I thought it was 11/32 but just wanted to make sure. And the package my tap came in did not give what size drill bit i needed to use for some reason.

Thanks,
cody

 

[Defiant]

Hm. Drill size is usually marked on the side of the tap.

 

[WhiteTsiAwd]

Taken care of. You can close it if you'd like.