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BrandonD 09-29-2012 05:28 PM

Drilling 1 1/2" hole through cinder block
I need to run conduit through my exterior wall of which I assume is cinder block (not sure how to tell if it's cinder vs concrete block). The outside diameter of the conduit is 1 and 1/2". I have access to a hammer drill but the largest bit from Home Depot/Lowes that I can find is 1". My questions.

1) Can I use the 1" bit and widen the hole with it and not risk damaging the wall?

2) What should I use to seal around the conduit if needed? Spray foam or a specific type of caulk? I'm hoping I don't have to... there is an LB fitting going inside on either side of the wall, so if I drill it just right it should be covered by the fittings.

3) Any general tips for the drilling?


oh'mike 09-29-2012 08:07 PM

I suggest you use a 1/4" bit and make a bunch of holes--then knock the plug out with a cold chisel----

joecaption 09-29-2012 08:17 PM

That's the way I do it, but I use a 3/8 bit so it last longer. Also make sure to drill the hole from the outside not the inside. The block under the house may blow out some and not look as good.
I use Hydrolic cement to clean up and seal it.

oh'mike 09-29-2012 08:54 PM

I only mentioned 1/4" because I always seem to have a bunch of that size--I use the for wall anchors ---

BrandonD 10-01-2012 07:57 AM

Thanks for the tips. I believe the guy I'm borrowing the hammer drill from already has 1/4" or 3/8" bit too, so that saves me from buying a bit!

user1007 10-01-2012 08:07 AM

If you wanted it pretty, you could step up to a carbide or diamond tipped hole saw for masonry and stone just larger than diameter you are running through it.

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