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Masonry Drill Bits for Concrete Block?

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[OP]
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Feb 20, 2015
1831 posts
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Southern Ontario

Masonry Drill Bits for Concrete Block?

My wall was drilled for RG6 Coax through the block/brick and was previously wired. I tried to fit a 2nd run of Coax cable through it and the hole is not big enough.

I don't have any long Masonry bits that I know of... could I use a long Slotted wood bit to make the hole bigger or would that be a waste of time? Long masonry bits look quite expensive and I'm assuming I need something about 12" long to make it through cement block and brickwork.

Any cheap way to make this hole bigger without ruining something?

I have existing wood/steel and Spade wood bits like this:

Image
10 replies
Sr. Member
Sep 5, 2011
835 posts
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Toronto
Your spade bits will not work. You will need a real masonry bit. And yes you will need a long bit. They are not that expensive. Depending on the sizes. They starts at around $10

1/2” x12” bit for $20

https://www.mississaugahardware.com/pro ... -drill-bit
Last edited by PCShutters on Sep 7th, 2021 7:37 pm, edited 1 time in total.
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Oct 2, 2018
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Toronto
Spade bits won't work, you'll just frustrate yourself and kill your existing bits.

I'd be hesitant to try a regular metal bit but it might work for a single hole even if you end up losing the bit itself. Cement block is fairly porous (comparibly speaking to other types of concrete) such as poured concrete slab so i have put some holes in this way in the past just will take a bit longer and dull the bit right out. I'd try that with a hammer drill if you have one. You are only talking 2 holes so worth the try. The wooden spade bit you show however i wouldn't try that at all the edge will keep grabbing and the kickback is going to be severe.

So go with a concrete bit, or potentially try a regular metal bit and see if that takes you. Drill the block hole larger from each side, then use a wire to tie onto the RG-6 and i think it should work out for you. The regular metal bit will be toast afterwards, but you have the option of sharpening or purchasing as they are much cheaper than a concrete bit. If you drill the block from both directions you will not require the standard 18 inch bit installers use. I would lend you my bit but i threw out two of my long 18" bits for this purpose when cleaning out my garage a year ago, my buddy has put aside a couple of these bits but i just haven't picked them up as i don't have need anymore. I will pick up however and store for the time i need.
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Sr. Member
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Oct 2, 2018
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Toronto
Another option is to just borrow a concrete bit from a friend, most garage guys have a few lying around and would be happy enough to lend one out seeing your task is so small. They would likely let you borrow the hammer drill same time.

I lend stuff out all the time to my buddies, makes sense as I love tools and might as well get some use seeing I'm a backyard mechanic will never put the mileage on them that they are capable of.
Youth is the gift of nature, while age is a work of art.
Deal Addict
Nov 24, 2015
1204 posts
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Durham Region
Just want to piggyback on this. Can anyone recommend a hole saw for making a 2” hole through red brick outside for HVAC intake pipe?

I have a Milwaukee hammer drill, so trying to use that if possible, but so far only found Bosch daredevil hole saw that is rated for masonry/brick. Any other options?

I know I can rent a SDS with a giant carbide bit, but trying to utilize what I have to make 1-2 holes
Member
Nov 10, 2015
335 posts
307 upvotes
Thornhill, ON
networksend wrote: Just want to piggyback on this. Can anyone recommend a hole saw for making a 2” hole through red brick outside for HVAC intake pipe?

I have a Milwaukee hammer drill, so trying to use that if possible, but so far only found Bosch daredevil hole saw that is rated for masonry/brick. Any other options?

I know I can rent a SDS with a giant carbide bit, but trying to utilize what I have to make 1-2 holes
You need a coring bit. Honestly for 2 holes it's better to pay an HVAC guy to do it for you. The coring bits are $250+ each. Would cost the same to have someone else do it for you. You also need an sds drill, regular hammer drill will not work.

Cheapest option is to rent the tool and bit.
Member
Nov 10, 2015
335 posts
307 upvotes
Thornhill, ON
OP, where are you located? Maybe someone on rfd can swing by and drill a bigger hole for you.

Or invest in the proper tools ( sds drill and bit)

Best to find a friend, rent the tools or pay someone a small fee to help out.
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Nov 12, 2006
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London
Ballroomblitz1 wrote: Spade bits won't work, you'll just frustrate yourself and kill your existing bits.

I'd be hesitant to try a regular metal bit but it might work for a single hole even if you end up losing the bit itself. Cement block is fairly porous (comparibly speaking to other types of concrete) such as poured concrete slab so i have put some holes in this way in the past just will take a bit longer and dull the bit right out. I'd try that with a hammer drill if you have one. You are only talking 2 holes so worth the try. The wooden spade bit you show however i wouldn't try that at all the edge will keep grabbing and the kickback is going to be severe.

So go with a concrete bit, or potentially try a regular metal bit and see if that takes you. Drill the block hole larger from each side, then use a wire to tie onto the RG-6 and i think it should work out for you. The regular metal bit will be toast afterwards, but you have the option of sharpening or purchasing as they are much cheaper than a concrete bit. If you drill the block from both directions you will not require the standard 18 inch bit installers use. I would lend you my bit but i threw out two of my long 18" bits for this purpose when cleaning out my garage a year ago, my buddy has put aside a couple of these bits but i just haven't picked them up as i don't have need anymore. I will pick up however and store for the time i need.
I'd do this, if you are going for the "discount method".
You should be able to get away without a hammer drill too.
Like stated, concrete block is relatively soft, as concrete goes.

As a desperation method (deserted island scenario), you may be able to enlarge with a chiseling method.
It isn't worth the effort here.

As an added note, alluded to by Ballroomblitz1, a spade bit is totally the wrong tool.
If this were wood, it would be the wrong tool.
There is no easy way to centre the bit, and it would jump around in a potentially dangerous way.
A cheat is to clamp a scrap piece over the hole to get it started and centred.
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Dec 27, 2007
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Edmonton
kammj1 wrote: You need a coring bit. Honestly for 2 holes it's better to pay an HVAC guy to do it for you. The coring bits are $250+ each. Would cost the same to have someone else do it for you. You also need an sds drill, regular hammer drill will not work.

Cheapest option is to rent the tool and bit.
Watch amazon. I got my 3-1/2" bit for $90. Made in germany

If he takes his time and uses adapters, maybe he can use a regular hammer drill?
It will definitely take a while.

Also of your handy, it will be cheaper to buy a broken/used rotary hammer drill and most likely you will just need some brushes (mine needed a piston and a couple orings) and you have a $1000+ tool for cheap. Much cheaper than renting
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Nov 24, 2015
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Durham Region
So even though it was not the fastest/best method, I decided to try what I already have on hand

What I ended up doing is made 12 holes in a circle pattern with 3/8 masonry bit and hammer drill, and chiseled out the hole afterwards

Even though I had a brand new decent quality bit and a fuel hammer drill, it still took a while since I had to let the bit cool a bit between holes and the drill after a couple.

So to conclude, it’s possible without coring bit/SDS, but much more time consuming and the hole was not as smooth after chiseling. Don’t really recommend this method unless you are in a pinch

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