Junction Boxes for Built In Oven & Range Top

[Buckaroo5]

For kitchen remodel, I am running 8-3 romex to junction boxes for built in oven & range top. They will be installed flush to rear wall of the cabinet. I would prefer to install 4 x 4 junction boxes to provide more room and I want to put a cover on it that has a centered 3/4" knockout for 90 degree flex conduit connector. I am not seeing these cover's readily available which make me think I am approaching this correctly. Suggestions please?

 

[malibu101]

Just drill or punch a 1 1/8" hole (3/4" conduit size) into a steel cover.
Done.

 

[MerlinsBeard]

You can find a step drill bit that goes up to 1 3/8". That's probably the cheapest option for a 1-of job.

If you have a lot of them to do, then depending on your budget, you may want to use a metal hole saw kit (mid-cost) or a knockout punch driver kit (high-end) (otherwise you'll deal with wear and tear on your reaming bits), e.g.

Budget - TEMCo TH0390
Midrange - Klein Tools 53732SEN
High End - Greenlee kit

One of these methods should allow you to make a hole in the cover cleanly. If you need to be more precise than the arbitrary sizes in a metal hole saw kit or punch kit, use a step drill bit (unibit) to expand the hole to size.

3/4" EMT outside diameter is supposed to be spec to 0.992" and 3/4" PVC schedule 40 outside diameter should be spec to 1.050".

 

[nadogail]

Blank covers are often made into “Special Purpose Covers” with the right shop tools.

 

[sparky 1971]

Don't use just a 4X4 box. Use a two gang mud ring on top of the box. Then get a two gang metal blank cover, I use weatherproof type and throw the gasket away, and drill a 1-1/8"hole in it. Also, make sure to use a 2-1/8" deep 4X4 and a 1-1/4" raised two gang mud ring to get the face of the box into the cabinet since you probably have 1/2" drywall and a 3/4" thick cabinet back.

EDIT: I screwed up and got confused by reading the post. I have never seen an oven or cooktop that needed a 3/4 knockout. Every single time, they have had a 1/2" flex conduit factory installed (about 7/8" diameter) a 7/8" hole is needed for this, and I like to use a 90° connector. If, in fact it is a 3/4 that is needed, a 1-1/8" hole is required, but I stand with my statement about 1/2" flex already there.

 

[sparky 1971]

You can find a step drill bit that goes up to 1 3/8". That's probably the cheapest option for a 1-of job.

A good 1-3/8 step bit is going to be somewhere around $75, definitely not the cheapest option when a hole saw could be used. I think that most people on this site should already have them, the proper size saw can be purchased for about $10 if he already has an arbor.. As far as I'm concerned, the only thing a step bit is good for is making an existing hole larger and I've been using them for 29 years. I prefer to use a carbide cutter, but they are size specific and about $25 each, not very cost effective for a one off job.. In this case, he would probably need a 7/8, but may need a 1-1/8 if it does happen to be 3/4 conduit size.

If you have a lot of them to do, then depending on your budget, you may want to use a metal hole saw kit (mid-cost) or a knockout punch driver kit (high-end) (otherwise you'll deal with wear and tear on your reaming bits), e.g.

Budget - TEMCo TH0390
Midrange - Klein Tools 53732SEN
High End - Greenlee kit

One of these methods should allow you to make a hole in the cover cleanly. If you need to be more precise than the arbitrary sizes in a metal hole saw kit or punch kit, use a step drill bit (unibit) to expand the hole to size 3/4" EMT outside diameter is supposed to be spec to 0.992" and 3/4" PVC schedule 40 outside diameter should be spec to 1.050".

The type of conduit has nothing to do with the hole size for a connector. 3/4", whether it be EMT, Rigid, PVC, or a plain 'ol romex connector requires a 1-1/8" hole. As I stated above, I'm willing to bet he actually needs a 7/8" hole for a 1/2" flex connector though.

 

[JordanOH]

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