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paulz
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# Posted: 1 Dec 2019 01:42pm
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I have a concrete bunker on my property, 14x14. It has a narrow 24" door that I would like to widen. 6" thick concrete.
Think with a 7" concrete blade on a Skill saw I could make vertical cuts on both sides of the wall (same side of the doorway)? Or will it bog down or overheat?
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toyota_mdt_tech
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# Posted: 1 Dec 2019 02:13pm - Edited by: toyota_mdt_tech
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Yeah, I saw concrete the other day with my own eyes. 
No, it will work, wet down the dust, its not only hard on the saw, its hard on you, look up silicosis.
That should work, cool having a bunker, make a nice root cellar maybe or a sweet cabin of sorts. 
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Nobadays
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# Posted: 1 Dec 2019 02:41pm
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I have cut a 6 inch vertical concrete wall before... to widen a doorway. As Brettny says, it is a tough job, but made easier with the right tool. Go to a rental place and get a 10 inch gas powered saw made for cutting concrete. It should have a place on it to screw in a garden hose. You need to run water on the blade the whole while you are cutting. Using an electric skill saw would be pretty dangerous when mixed with water! Don't know how old you bunker is but likely that concrete will be very hard. A gas saw with a diamond blade is your friend here.
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ICC
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# Posted: 1 Dec 2019 03:01pm - Edited by: ICC
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I would do as Nobadays suggests. Rent a saw made to cut concrete. You will need a water supply, that is critical. Using a skilsaw for a job like that is not recommended. Maybe for cutting a concrete patio block or two, but not serious concrete like your bunker wall. And hope they did not use a lot of rebar
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paulz
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# Posted: 1 Dec 2019 05:25pm - Edited by: paulz
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Thanks guys. I do have this Stihl saw I used on my paver project, just not sure I could hold it up for the time it would take. It has a14" blade and is pretty, um, exciting when it gets on the power band. It has a water hookup but I don't have the bottle and hose that goes to it.
TMT, what it is is more correctly a bomb shelter, per the original plans. My property had a house on it, built in 1960. All that remained when I bought it was the foundation and the shelter. As of a week ago it's now my carport.  
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Nobadays
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# Posted: 1 Dec 2019 06:33pm
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Paulz... yep that is what I used, and yes it is pretty hard work to make a vertical cut. I had two arms when I did this years ago. Maybe counter-weighted rope and pulley system? Good luck on it!
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Brettny
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# Posted: 3 Dec 2019 07:11am
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If you dont care about how smooth the cut is and have more time than arm strength yes a circular saw will work ok. A gas or electric demo saw is what i would use if i cared about the finish.
I have a 10in worm drive circular saw. Man is that thing dog slow to cut concrete.
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paulz
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# Posted: 29 Jan 2020 06:23pm - Edited by: paulz
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Got started on my door widening project this morning. I bought a cheap $20 7 inch blade at HF and put it on an old lightweight sidewinder saw. Cut much better than I figured, about a half hour to cut one side and still cutting as well at the end as the start. Blade never got hot enough not to touch. The blade is turbocharged, says right on it.
Only 2.5 inch depth though, wall is 8 inches thick.
So I might cut the other side, then try some wedges in the cut to crack middle 3 inches. Or get the Stihl 2 stroke with 14 inch blade, since now at least there's a cut to follow. And hopefully the floor was a separate pour (must have been) with maybe some rebar to cut, since I can't saw that.
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Nobadays
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# Posted: 29 Jan 2020 07:31pm
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That's a big "door widening! " looks like another full door width opening. If you want to break that out it might take a few more vertical cuts.
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paulz
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# Posted: 29 Jan 2020 08:01pm
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Yeah, it was originally a bomb shelter, built in 1960. 12x12 I think. Here is the original blueprint, and the wall I am taking out. I don't know why it was built like that but i'm using it for a storage room and it's a pain in the butt wiggling things through that little hallway.
When I get it cut on the other side my plan is to take my biggest sledge and work out my frustrations. Also have a 40 lb. electric demo hammer with a chisel bit but that's not likely to do much.
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sparky30_06
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# Posted: 30 Jan 2020 06:53am
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be careful widening it that much, you may loose too much structure to support the roof. You will want to cut completely through before taking your sledge hammer to it.
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paulz
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# Posted: 15 Feb 2020 09:48pm - Edited by: paulz
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Think it will be OK Sparky, it's an interior wall and the concrete roof is the same everywhere. I am wondering about the huge chunk of concrete I'll have to deal with.
I bought a new 14" diamond blade for the Stihl 2 stroke saw, burned up the old one cutting pavers dry. I want to hook up the water, it has a valve on it with a hose leading to the blade.
How much water does it take? I don't have pressurized water where I'm at. Would gravity feed be enough, or how about a garden sprayer?
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ICC
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# Posted: 15 Feb 2020 10:31pm
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Quoting: paulz How much water does it take? I don't have pressurized water where I'm at. Would gravity feed be enough, or how about a garden sprayer?
We used to have a Skil 700 and ran about 5 gallons a minute of cutting time. Used a pump. I don't know if gravity flow could get that volume? It kept the dust to about zilch which was a big part of the reason for the volume.
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paulz
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# Posted: 16 Feb 2020 12:32am
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Ew, 5 gallons a minute, can't do that with a garden sprayer. I could truck a 55 gallon barrel to where I could gravity feed it. I will try a test..thanks ICC
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NorthRick
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# Posted: 16 Feb 2020 02:40pm
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I don't think you need any where near 5 gpm. I rigged up a chop saw to cut pavers and had a tube that dribbled water onto the blade. I think you could rig up a gravity feed system that would work just fine.
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paulz
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# Posted: 16 Feb 2020 04:50pm
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Thanks Rick, got sidetracked today at a moving sale, gravity feed test tomorrow. One thing I'm looking forward to will be less dust. I made the first 2.5 inch cut dry and what a mess. Had a decent particle mask on but probably not as good as it should be.
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ICC
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# Posted: 16 Feb 2020 05:09pm
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I looked in the manual and found where it states a minimum of 20 ounces of water a minute to keep the dust down to acceptable OHSA standards. I think we ran lots more water because we found that blades lasted much longer and also that more water cleared the work area better. We mainly cut concrete floors, driveways and curbs. I don't recall exactly because that area was my brothers' responsibility.
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Brettny
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# Posted: 18 Feb 2020 07:45am
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A flooded blade will last longer and make A lot less dust. Flooding the blade will be hard to do on a vertical cut.
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