Quick question re: conduit box hole ID

[TT_Vert]

I accidentally knocked out the larger part of a 1/2" knockout while trying to get the 1/2"er out. So now I need go get reducing washers. My question is, is the washer based on the ID of the hole? The reason I ask is that the ID is 1 1/4" but it seems HD stocks the 1" to 1/2" but none of the 1 1/4" washers which leads me to believe the 1 1/4" is not that common, so I want to confirm these washers need the ID of the hole that it needs to reduce? If so I'll just order some 1 1/4 to 1/2" reducing washers unless anyone knows other places that may stock this size. Doesn't seem like lowes or menards does either.

Thanks
Dave

 

[engineer2]

Household electrical boxes generally have knockouts for 1/2" and 3/4" fittings. If that is the case you would need a 3/4"-1/2" Reducing Washer - Menards # 365-1058

Curious: Are you metal conduit or Romex? I seem to recall Wauconda and/or Island Lake allows Romex.

 

[TT_Vert]

It's not a 3/4". I have one hole w/ a 1/2" | 3/4' knockout and the other is 1/2" | 1" it appears after looking at the NEMA specs for nominal ID of conduit fitting holes what I have is a 1" (NOT the 1 1/4" I assumed based on the ID of the hole) knockout, i just couldn't measure the ID precisely w/ it in the wall. I'm all conduit, this is newer construction. Fortunately this entire house is conduit. I did run a few short BX whips for some additional lighting but it's all w/in code.

Dave

 

[engineer2]

You might need a 1"-1/2" Reducing Washer - Menards SKU: 365-5711

Lots of good electricians here at GJ. I'm sure they'll be chiming in when they get off of work.

 

[alfredeneuman]

A standard 1" conduit knockout is about 1-1/4" in diameter.

 

[mm08822]

They are spec'd by conduit size. Knowing the ko diameter is needed to figure the conduit size if you cant tell by eye..........
1/2" c = 7/8" hole
3/4 = 1-1/8"
1" = 1-3/8"
etc..............

 

[TT_Vert]

Thanks that's what I found. I got a 1" reducer last night, i'm going to try it in a few.

Dave