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What are everyone's tips and tricks for punching larger holes, like for conduit, through block walls without having it chip out and look like you did it with a chisel and a hammer. I do lots of anchor bolt holes etc but I've never really done any wall penetrations for conduit or etc. Around the plant we have some that look good while others are chipped back from the hole 4 times the size of the hole. What's the secret ?
 

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Yeah we have some different length 1/4" SDS plus and we'll run that then follow up with a SDS max dry core from both sides.
I think this is a better way in general, drilling from both sides.

I usually use the SDS plus thin wall core bits for block, they're perfectly adequate for most block, even with a cordless SDS plus drill. I have tried both the Bosch and the Milwaukee, they're both pretty good but neither is perfect. (See SDS Plus Thin Wall Core Bits ) . There's less hammering impact with SDS plus than SDS max so they should blow out a lot less even if you went straight through both sides.

I bought a long small diameter SDS plus bit to use as a "feeler" so I don't have to use two drills. I use the feeler more to make sure I find the right block on the other side, and see if there's any surprises inside the block. (Ever run into block filled with vermiculite?) But I don't use the hole on the other side as a pilot hole, it's usually off since you never drill quite square and level. I'll measure the cell on the other side and make the hole in the same spot.

If it's out of sight above a ceiling or etc., or if it's just easy to see which block is the right block on the other side, I might not bother with the pilot hole and just measure for the location of the starter hole on either side of the cell.
 

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Yeah we have some different length 1/4" SDS plus and we'll run that then follow up with a SDS max dry core from both sides.
This is how I do it. If for some reason I don't have enough space on both sides for the drill I still drill with the small pilot hole first. Use the drill bit to measure the exact thickness of the wall.and then mark it on my core drill. Once my core drill gets to about one inch from punching trough I turn it off hammer mode and use light pressure.
 

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First step is to determine the block type, to avoid the webs for a clean hole or a series of them in a tight formation. The outside dimensions of the block will usually tell what type of block it is.

In my work have done many jobs that required 3 or 4 runs to the same piece of equipment, motor, control, heaters and pneumatic tubing. I always laid out the runs and holes in a tight formation so that they could be placed in one or two blocks and could be strapped with a strut rack easily on the other side , to reach the equipment with minimal fuss and extra offsets for a clean and sturdy install.

I use a 18" long 1/4" masonary pilot drill in a regular hammer drill to do the initial location. This is to help you locate the exact block on a large wall with little other references from inside to outside. I use my block dimension drawing scribbled in my old Ugly's reference to determine where to layout my runs to avoid the web locations for all of the required runs.

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When laying out the locations and the hole centers on one side, I make a cheat sheet of the hole centers from the corners of the block, to use to transfer the exact centers to the opposite side of the block. Then drill the holes from both sides to avoid the block blowout and keep the runs level and parallel for strapping the group together, or to the equipment.

If you don't have a core drill or an SDS bit of the proper size to use, a 1/4" x 4" drill can be used to make a large or odd shaped hole if you draw the fitting size around your center marks and making multiple small holes and cleaning out between them. For me the extra time spent doing the layout and drilling is compensated for by just being able to seal it up with a caulk gun instead of a bucket of mortar and a can of paint.

Your finished results speaks volumes about what kind of work you do. If the cold and snow is blowing in all winter long, you wont be highly regarded for the next project.
 

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If you have several conduits that will pass through, you could remove the complete block. Depending on the situation, you may need to frame it with 2x8's. Then you have a chase and it looks like it belongs.
 

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Discussion Starter · #10 ·
If you have several conduits that will pass through, you could remove the complete block. Depending on the situation, you may need to frame it with 2x8's. Then you have a chase and it looks like it belongs.
This sounds like a great idea for internal walls.
 

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I bought a long small diameter SDS plus bit to use as a "feeler" so I don't have to use two drills. I use the feeler more to make sure I find the right block on the other side, and see if there's any surprises inside the block. (Ever run into block filled with vermiculite?) But I don't use the hole on the other side as a pilot hole, it's usually off since you never drill quite square and level. I'll measure the cell on the other side and make the hole in the same spot.
Yes I have hit vermiculite, 1/4" hole is better than 2". Was a time I carried a small piece of duct seal just in case to shove in the hole, otherwise your standing with your finger in the dike waiting for some else to come along because by the time you got back it was too late. I also agree on the don't use the pilot hole. This did burn me once when I measured the web and it turned out they built two wall next to each other with smaller block that were off joint wise but close. We just thought it was 12" block not 8" with a 4" face
 
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Yeah we have a SDS plus arbor too, a fuel roto hammer will do pretty good, I put a 2 9/16" thru split face veneer, cmu then 5/8" rock on the other side the other day with one.

We use the max a lot tho in places we can't or don't wanna use the wet core rig on concrete. Put one of those cores on a 15 pound roto and you can do some damage lol.
 
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