# Cable connector for 7/8" (actual size) knockout



## notadoktor (Jul 19, 2017)

I recently installed some 2 lamp, LED ready fixtures. I ran the NM-B wiring through the attic to the lights. I used one of the knockouts to pass the wires into the fixture. After finishing I realized I need to add a cable connectors to the fixture for the wiring.

My problem is that I am having difficulty understanding/finding the correct size clamp. From the research I have done it seems like I need some 1/2 cable connectors to fit the 7/8" knockout but I can't find any in that size. I've only had luck finding 3/8 and 3/4. I have found plenty of EMT fittings but I don't have conduit.

I'm thinking of just enlarging the knockout with a hole saw and use a 3/4 cable connector but I wanted to ask before I go through all the trouble.

Appreciate all the help! Thanks!


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## Jim Port (Sep 21, 2007)

Just use a 3/8 connector.


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## notadoktor (Jul 19, 2017)

Jim Port said:


> Just use a 3/8 connector.


Oh wow I feel silly. So when the 3/8 connector says it fits a 1/2 knockout, the 1/2 knockout is actually 7/8"?


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## Oso954 (Jun 23, 2012)

It's a trade size not a measurement.
Next time you are in a store look at 1/2 rigid conduit. The 1/2 inch is the id, then you have the wall thickness that the treads are cut into. Those threads need to fit the hole.
So yes, the 1/2 knockout hole is 7/8.
The 3/4 knockout hole won't come out as a decent fraction, but it is 1.109 inches. 

Here are the nema standards on knockouts/fittings, if you are interested.
https://www.nema.org/Technical/Documents/Bull_71_reaffirmed_12_15_11.pdf


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## J. V. (Jun 1, 2007)

notadoktor said:


> Oh wow I feel silly. So when the 3/8 connector says it fits a 1/2 knockout, the 1/2 knockout is actually 7/8"?


Yes that is correct.


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