Why Is A 1/2" Knockout 7/8" In Diameter? - Electrical - DIY Chatroom Home Improvement Forum


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 05-25-2012, 08:09 PM   #1
Member
 
Join Date: Mar 2009
Posts: 112
Rewards Points: 75
Default

Why is a 1/2" knockout 7/8" in diameter?


Silly question, I know.

Advertisement

smata67 is offline   Reply With Quote
Old 05-25-2012, 08:13 PM   #2
Member
 
Missouri Bound's Avatar
 
Join Date: Apr 2011
Location: Almost Arkansas
Posts: 2,764
Rewards Points: 2,000
Default

Why is a 1/2" knockout 7/8" in diameter?


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"?

Advertisement

__________________
Do you want it your way or the right way?
Missouri Bound is offline   Reply With Quote
Old 05-25-2012, 08:25 PM   #3
Member
 
Join Date: Nov 2011
Location: Hartfield VA
Posts: 27,778
Rewards Points: 672
Default

Why is a 1/2" knockout 7/8" in diameter?


Works the same with all pipe fittings.
joecaption is offline   Reply With Quote
Old 05-25-2012, 09:08 PM   #4
Member
 
Join Date: Mar 2009
Posts: 112
Rewards Points: 75
Default

Why is a 1/2" knockout 7/8" in diameter?


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.
smata67 is offline   Reply With Quote
Old 05-25-2012, 09:43 PM   #5
Member
 
Missouri Bound's Avatar
 
Join Date: Apr 2011
Location: Almost Arkansas
Posts: 2,764
Rewards Points: 2,000
Default

Why is a 1/2" knockout 7/8" in diameter?


Quote:
Originally Posted by smata67 View Post
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.
__________________
Do you want it your way or the right way?
Missouri Bound is offline   Reply With Quote
Old 05-26-2012, 08:24 AM   #6
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Why is a 1/2" knockout 7/8" in diameter?


Quote:
Originally Posted by Missouri Bound View Post
It's a "nominal" measurement.
Yes, nominal (named) vs. actual. And a 2x4 is not 2" x 4".
Yoyizit is offline   Reply With Quote
Old 05-26-2012, 12:38 PM   #7
Master Electrician
 
Join Date: Mar 2010
Location: Toronto Ontario
Posts: 1,165
Rewards Points: 500
Default

Why is a 1/2" knockout 7/8" in diameter?


for anyone interested

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

Advertisement

__________________
Sarcasm is my friend
I'm here to learn too, i do mostly commercial/industrial/new construction and this place is a great way to pick up tips on residential from some good electrical minds. Excuse the spelling, my phone has a mind of it's own.
andrew79 is offline   Reply With Quote
The Following User Says Thank You to andrew79 For This Useful Post:
kbsparky (05-26-2012)
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
diameter size for drapery rod fdf47 Interior Decorating 4 04-14-2011 08:49 AM
Installing bathroom sink - drains off slightly less than pipe diameter lazzlazz Plumbing 17 05-21-2010 06:12 PM
1/2" diameter hole in hollow core door noahweb Carpentry 4 02-16-2010 09:36 PM
Duct Diameter Reduction Earnie HVAC 4 01-27-2010 03:52 PM
Framing Gun - Nail Shank Diameter Questions... MoparAutoworks Building & Construction 5 07-03-2006 10:27 PM




Top of Page | View New Posts