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Doing old work with 12 AWG cable makes finding large enough boxes tricky. I have seen some appealing metal boxes, but I am wiring using NM cable (Romex), which needs cable clamps where it enters a metal box. I can't find these anywhere!

Some metal boxes come with them, but those are generally single-gang boxes of less than 17 cu.in., which is not enough for me. Several different attempts at searching Home Depot and Lowes' sites turned up plenty of conduit clamps (the ones like a strap with a U in it where you screw down the flat part with the conduit under the U), but no, zero, absolutely none of the two-part NM cable clamps with locknut on the inside that I needed. I found a couple huge ones (1-1/2 in, 2 in) from Halex, but none fitting the 1/2-in knockouts that are all I need.

Is there some secret place where all the cool kids buy their workaday electrical supplies that I should know about? Some magic name that I need to use to look it up? I just need bog-standard utilitarian cable clamps, not 200 options for decorator cover plates, but the latter is what the Web seems to want to sell me.

Alternatively, is there some other legit way I could protect NM cable entering a metal box that would avoid the need for this amazingly hard-to-find part?

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The lesson is: don't research products at 3 in the morning. The other lesson is: if you create a website listing electrical products, make the sizing info jump out at people, don't make them go hunting. –  Jeremy W. Sherman Jul 16 '12 at 21:10

2 Answers 2

up vote 5 down vote accepted

Halex 3/8 in. 2-Piece Clamp Connectors

enter image description here

Product Description: Use the Halex 3/8 in. 2-Piece Clamp Connectors (5-Pack) to connect #14 - #10 non-metallic sheathed cable to steel

outlet boxes or other metal enclosures. They are compatible with standard 1/2 in. knockouts.

  • Secure #14 - #10 non-metallic sheathed cable to steel outlet boxes or other metal enclosures
  • Zinc-plated steel resists corrosion
  • Fits standard 1/2 in. knockouts
  • For indoor use only
  • Designed for easy installation
  • MFG Brand Name : Halex
  • MFG Model # : 26510
  • MFG Part # : 26510

Or as @Aaron suggested

Halex 3/8 in. Twin Screw Non-Metallic Cable Clamp Connectors

enter image description here

Product Description:

Twin Screw Non-Metallic Cable Clamp Connectors to join non-metallic sheathed cable and flexible cord to steel outlet boxes or other metal enclosures. A reversible locknut cuts through protective coatings on boxes and enclosures to preserve grounding.

  • Connect non-metallic sheathed cable and flexible cord to steel outlet boxes or other metal enclosures
  • Body and locknut are die-cast of high-strength zinc alloy
  • Zinc-plated steel clamp and screws
  • Reversible locknut cuts through protective coatings on boxes and enclosures to assure ground continuity
  • Fits 1/2" knockout
  • For indoor use only
  • Screws compatible with Phillips, slotted and square screwdrivers
  • Resists corrosion
  • UL and CSA safety listings
  • MFG Brand Name : Halex
  • MFG Model # : 20511
  • MFG Part # : 20511
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D'oh. That was the secret sauce: the size listed is the inner diameter, not the exterior diameter AKA the knockout size. Thank you! –  Jeremy W. Sherman Jul 16 '12 at 21:07
    
@Tester; don't we wish they were all that simple to solve. LOL. Great references and photos. –  shirlock homes Jul 17 '12 at 10:25
    
If you're just clamping down NM cable, not AC, then you can use pop-in Hit Lock Connectors instead of the clamps. They snap into the knockout to protect the sheathing from the metal and have a few plastic fingers that grip inserted cable to keep it from being pulled out, much like the knockouts in NM boxes. These are easier and faster than the old clamp + locknut combo. –  Jeremy W. Sherman Jul 27 '12 at 19:47

Do you mean one of these? (just so we're clear we're talking about the right thing)

enter image description here

I picked up a bag of them at Home Depot. I don't recall off the top of my head if it was 1/2 inch or not, though. You may want to google 'electrical supply store' and your zip code and see what that turns up, but what you're describing doesn't sounds like it is that hard to find.

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