Drill bit size

[caryain]

I am going to install my guages tomorrow and can't find my cheat sheet telling me what drill size to use for 1/8" NPT fitting. I'm sure someone here will know this right off the top of their head.



Thanks in advance.

Chip

 

[Bob Wagner]

"R"

 

[Dieselnutz]

Check out this link! http://www.engineersedge.com/tap_drill_chart.htm



Letter size R

 

[mediccummin]

You can count on Bob for the answer, he's the man.



And thanks for the chart Dieselnutz.

 

[krs]

"what drill size to use for 1/8" NPT fitting"



It's not on the tap? I've never seen a tap that didn't have the drill size to use engraved on it's shank. Even the little ones do, though no one can read them.

 

[Rman]

I drilled my valve cover last week for an oil bypass with a 1/8 npt fitting. I used Letter R like bob said. Worked like a champ. Nifty chart!!!

 

[nickleinonen]

11/32" works well too [for 1/8"npt]... and 7/16" for 1/4"npt





and i thought the letter size for 1/8"npt was Q ???

 

[JRMora]

Originally posted by nickleinonen

11/32" works well too [for 1/8"npt]... and 7/16" for 1/4"npt





and i thought the letter size for 1/8"npt was Q ???

Me too. When I did my gages, I used a "Q" for my 1/8"-NPT fitting on the pyro. The cross reference chart in Grainger's catalog said that was the one. No fit up problems for me.



Juan

 

[caryain]

Thanks for all the responses. I used Letter size "R" and it worked great.

 

[Rman]

Originally posted by JRMora

Me too. When I did my gages, I used a "Q" for my 1/8"-NPT fitting on the pyro. The cross reference chart in Grainger's catalog said that was the one. No fit up problems for me.



Juan

I think any of the three will work. I've seen Q, R, and on a "set" which included the tap and drill bit I've seen a 11/32"... .



they're all within a low number of thousandths of an inch, so really it's all close. The NPT style of threading, being tapered, it's not that critical anyhow. My R size bit felt quite snug as I tapped it. I lubed it well and turned our just fine.

 

[2broke2smoke]

good reference dieselnutz

 

[kboettcher]

My 1/8 NPT tap has 21/64 etched right into it. I use it all the time at work and it has always worked great.

 

[JohnE]

And an "F" drill to open up the 1/8" compression fitting if you don't get one in the gauge kit.