I'm trying to do a wiring for a dishwasher outlet and need to install a new circuit for it.

The only option is to go under the subfloor on a concrete slab. The floor is 3 inch high so the conduit should be fine to fit in. The only problem is that there is a firebreak 6 feet away and I need to drill a hole.

Is there a tool that could do this. I was actually thinking of using the conduit or other metal pipe with some type of hole cutting attachment. Connect to a drill gun and do it that way.

  • 2
    I have cut teeth onto the end of a pipe and drilled a hole through wood. Won't do many but 1 is usually fine.
    – Solar Mike
    May 17, 2023 at 17:32
  • Sounds like you need an appropriately sized rifle.
    – Hot Licks
    May 17, 2023 at 22:25
  • Not clear what you mean to do...you need to cut through concrete, or wood? Gotta sketch?
    – Huesmann
    May 18, 2023 at 13:33
  • @HotLicks, the dynamite would be a better option. Lol
    – Grasper
    May 18, 2023 at 15:18

2 Answers 2


Big-box and electrical supply stores sell a set of (usually) two drill bit extensions, about 4 feet long each one. These can be stacked together, to produce 8 feet or so of total length. The extensions are fairly flexible, allowing them to curve around corners to transition from a room to in-wall travel. They typically have a long-ish metal "chuck" on the leading end that can secure a drill bit using one or two set screws. You put the bit into place, tighten the set screws from the side, and hope that you've tightened them enough. Personally, I recommend you apply some thread-lock to the set screws.

The "pro" trick is not to just use the drill bit extensions. Get yourself something that is just the right size, like a tennis ball or raquetball (squash?). Or a golf ball, if the gap is really tight. Drill a hole through the center, and use the ball as a spacer to ensure your hole is drilled roughly at the midpoint of your space.

As far as "will it fit conduit?" that depends on the drill bit you choose. Doing this at all is a pain in the ass. Doing it twice to enlarge the hole would be a nightmare. So make sure you use a large enough drill bit the first time!


You can get long drill bits that fit a standard drill and are made for running wires through walls.

One example I found at Amazon is 72 inches long with a head like this:

drill bit augur head

  • will that be wide enough for a conduit? But good suggestion though. Do any rentals carry this?
    – Grasper
    May 17, 2023 at 17:03
  • They're available in a fairly wide range of sizes. You'd have to ask the rental companies in question whether they have these.
    – keshlam
    May 17, 2023 at 22:01
  • Most rental companies rent tools and sell bits/blades. Because users commonly destroy bits/blades.
    – Ecnerwal
    May 18, 2023 at 13:23

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