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-   -   Why is a 1/2" knockout 7/8" in diameter? (http://www.diychatroom.com/f18/why-1-2-knockout-7-8-diameter-144844/)

smata67 05-25-2012 08:09 PM

Why is a 1/2" knockout 7/8" in diameter?
 
Silly question, I know.

Missouri Bound 05-25-2012 08:13 PM

The inside diameter of the typical 1/2" conduit is 1/2". Therefore all fittings which would fit the same size hole as one for 1/2" conduit are refferred to as usable in a 1/2" KO. Why does a nut for a 1/4" bolt measure 7/16"?

joecaption 05-25-2012 08:25 PM

Works the same with all pipe fittings.

smata67 05-25-2012 09:08 PM

So fittings that screw into the "1/2" knockout end up with 1/2" clear opening. I'll verify tomorrow when I'm back on the job.

Missouri Bound 05-25-2012 09:43 PM

Quote:

Originally Posted by smata67 (Post 928756)
So fittings that screw into the "1/2" knockout end up with 1/2" clear opening. I'll verify tomorrow when I'm back on the job.


It's a "nominal" measurement.:thumbsup:

Yoyizit 05-26-2012 08:24 AM

Quote:

Originally Posted by Missouri Bound (Post 928791)
It's a "nominal" measurement.:thumbsup:

Yes, nominal (named) vs. actual. And a 2x4 is not 2" x 4".

andrew79 05-26-2012 12:38 PM

for anyone interested

http://www.home4c.com/conduit.htm


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