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I am building a brick wall from concrete blocks. Note that these concrete blocks just provide a facade, don't hold any weight except an additional layer of same bricks above them.

The blocks are 4" high, I want to run a 2" pipe through the middle. The 2" PVC pipe should fit snugly. Is there any certain kind of drill/bit I should add to my electric drill to do this work?

I have a very cheap corded power drill and a battery-powered one as well.

Is there a certain kind of drill bit I should add to my electric drill to do this work?

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  • This is unlikely to work with the tools you have. Is this wall going to be free-standing or will there be soil on one side or something else, like a retaining wall? Apr 9, 2021 at 15:18
  • The wall is glued with PL 500. The pipe serves to drain water which is behind it, but this actual brick is just a facade, other materials, rebar, metal, larger cinder blocks, etc. behind it provide the real strength.
    – Village
    Apr 9, 2021 at 15:46
  • Note the key point of isherwood's answer - unless there will be a hole in the top block, none of them will be visible, so it doesn't matter if they're clean or ragged.
    – FreeMan
    Apr 9, 2021 at 16:01
  • If you mean a horizontal hole, through the facing side, I think you'll crack the brick. Perhaps putting the pipe between two bricks is more doable. You could even stack two pipes so it would look like you meant to do that. Apr 10, 2021 at 14:41
  • Note that a 2" hole through a 4" brick will leave less than 1" above and below the hole. It's going to be difficult to drill such holes, even with the proper masonry bit.
    – Hot Licks
    Apr 11, 2021 at 1:35

4 Answers 4

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To make a clean, precise hole in concrete, use a diamond core bit. Your small, cheap drill probably does not have sufficient torque and runs too fast for a core bit this large. But you can rent a heavy duty drill and core bit.

Wikimedia Image enter image description here

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    A shop that supplies the garden water feature/fountain landscape industry may offer core drilling of boulders -- or precast concrete blocks -- as a service. This could be an alternative to your (excellent) suggestion of renting the equipment for the job.
    – Greg Hill
    Apr 9, 2021 at 15:39
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MTA gave the right answer about the bit. Make sure you get diamond (see his answer for what it looks like) and not tungsten carbide (pictured below).

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Also make sure the bit fits on the drill, and check you have the correct adapter before leaving the shop!

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Professional diamond core bits use a special screw mount to the special huge and powerful drill that is used to spin them. For 2" hole you don't need to pay extra to get that. You can spin them with a drill, but it needs torque, so it has to be a drill with a gearbox. If you use your typical hammer drill, it will spin very fast, which will be dangerous, and it won't have torque at low speed.

I use a rotary hammer drill for this, in first gear, with the hammer action set to OFF obviously! It turns nice and slow, with good torque. You need to stick a big sponge full of water inside the bit, so it gets squeezed and the water released as it bites into the material.

In fact, since you will need to make a center hole with a drill first, I'd recommend renting (or purchasing) a SDS rotary hammer drill. Then either get a diamond core bit with a SDS adapter (picture above) or a hex adapter, but your drill will need a hex chuck on top of the SDS chuck.

If the diamond bit does not have a center alignment bar poking out of it, clamp some pieces of wood on the workpiece to make a guide. You can make a triangle with 3 pieces of wood, that will hold the diamond bit cylinder in place while starting the hole.

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  • This. Except what's up with "the hammer action set to OFF" ?
    – Mazura
    Apr 10, 2021 at 19:08
  • Well a diamond bit works by friction, not hammering, so you have to set the "hammer" knob to "off" otherwise it'll make a mess. I use the big rotary hammer drill for this not because it has a hammer, but because it has a gearbox with a first gear which is just the right speed with lots of torque.
    – bobflux
    Apr 10, 2021 at 22:00
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MTA's answer is the best plan if you care what it looks like. If the hole will be covered, a series of 1/4" or 3/8" holes drilled with a common masonry bit in a ring will allow you to punch out the center. All the holes in the ring should be outside a 2" circle to minimize the amount of cleanup you have to do after knocking the center out.

You wouldn't want to do this in large-aggregate concrete or stone, but these pavers are soft enough that for one hole you can make it happen. Keep your bit cool or you'll melt it. Dunk it in water every few seconds, before it gets raging hot.

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    But with a hammer drill - a regular drill will not be up to the task Apr 9, 2021 at 15:44
  • It can be done without hammer action. Like I said, these things are soft. It'll take a while, but still might be quicker than driving to a shop for tools or service.
    – isherwood
    Apr 9, 2021 at 15:44
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    The most important part of this answer is that the hole will be hidden so there's no need for it to be clean as the OP desires. Maybe the hole at the top where it's visible should be clean for cosmetic purposes, but after that one, who the heck cares!
    – FreeMan
    Apr 9, 2021 at 16:00
  • Coring bits are better for clean holes, but I'd just like to note on this answer that this is a viable way to get a clean hole as long as it doesn't need to be clean deeper than about 2 inches. I've had to drill holes this way in landscape block, cinderblock, mid and high strength concrete and even finished stone. It can absolutely be done with a low error rate and clean finish, it's just time consuming and requires a bit of hand chisel work to clean up the hole. Using a hammer drill capable of soft hits to start the hole helps.
    – K H
    Apr 11, 2021 at 8:56
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If you are building a retaining wall you may be able to run the pipe under the bottom or around the edge vice drilling through (you do need to ensure your drainage pipe has a slope). I'd also look into the 4" perforated pipe + sleeve vice 2" PVC

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