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Plunge grooving aerated concrete

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  • Plunge grooving aerated concrete

    Wife wants to remodel the bathroom, and I was assigned the job of running 50mm pipe inside the wall. The wall is made up of aerated concrete:



    This material is easily cuttable with regular hacksaw blades. The blade gets dull after a while, but most of the time, you finish the jog before it is dull. Obviously, I can't cut a groove using a hacksaw blade.

    Using an angle grinder with a diamond wheel would work, but this generates enormous amounts of dust and I'll have zero visibility after a few second. There are groove cutters with dust extraction, but I'd rather not pay $1000 for one.

    So, I am contemplating using my jigsaw to plunge cut into the wall using either a metal or a wood blade. Given that the other end of the blade won't emerge from the other side of the wall, will this work?

  • #2
    Generally... no. Try it, you'll see why (it bounces on the end)

    If you don't have one, rent the right tool. Two grooves to depth (wet or dry depending on what you rent), then sharp cold chisel and it will all be out.

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    • #3
      Thermalite block. We have a particular machine for chasing that stuff, it looks like a wide 2 handled portable belt sander but instead of a belt it has a platen on the bottom and a tungsten toothed wheel poking out the base which turns at about 69-100rpm at a guess. You plunge it into the wall and drag it down. It churns the block out without creating much airborne dust just has a constant stream if heavy granules fall out into a pile on the floor.
      Peter - novice home machinist, modern motorcycle enthusiast.

      Denford Viceroy 280 Synchro (11 x 24)
      Herbert 0V adapted to R8 by 'Sir John'.
      Monarch 10EE 1942

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      • #4
        Originally posted by Peter. View Post
        Thermalite block. We have a particular machine for chasing that stuff, it looks like a wide 2 handled portable belt sander but instead of a belt it has a platen on the bottom and a tungsten toothed wheel poking out the base which turns at about 69-100rpm at a guess. You plunge it into the wall and drag it down. It churns the block out without creating much airborne dust just has a constant stream if heavy granules fall out into a pile on the floor.
        Hmm, that makes a lot of sense. I'll do some google fu to see if such a tool is available here... Do you remember a brand name?

        I also considered using a hammer drill, but this will remove too much material and also might cause unwanted cracks ...

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        • #5
          Found this one, available here:

          http://www.youtube.com/watch?v=P3dn8Yxe6Es

          But $1500

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          • #6
            Several people make them, I can't remember what ours is but this is the type of tool

            http://www.macroza.com/en/products/m...llChasers.html
            Peter - novice home machinist, modern motorcycle enthusiast.

            Denford Viceroy 280 Synchro (11 x 24)
            Herbert 0V adapted to R8 by 'Sir John'.
            Monarch 10EE 1942

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            • #7
              There is apparently also a hand tool for this job, not sure of its performance, though

              Last edited by taydin; 03-15-2013, 03:00 PM.

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              • #8
                Could you rent one? Maybe from a seller of the block?
                "Let me recommend the best medicine in the
                world: a long journey, at a mild season, through a pleasant
                country, in easy stages."
                ~ James Madison

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                • #9
                  Originally posted by flylo View Post
                  Could you rent one? Maybe from a seller of the block?
                  AFAIK only Bauhaus (similar to Home Depot) has rental and they don't have grooving tools for rent.

                  I think I will try bending a U shape like in the picture in #7 using 1mm sheet metal and attach a handle to it. Whenver it dulls out, I can use a round file to sharpen in

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                  • #10
                    If you don't have lot of it, they do make a thermalite saw - like a regular hand saw with carbide teeth. Cuts blocks with ease though not very suited to cutting walls and the mortar joints will make you sweat.

                    If you fancy just breaking them out, I would mill out a chisel tip from ordinary mild steel and weld it onto a worn out chisel. Either take a block of steel the width of your chase and mill some slots in it to make thin webs with wider gaps and stick on some side relief or make it a U-shape so every time you present it to the wall it cuts a scollop of block out. If your wall is less than 4" thick go very easy on it with the breaker.
                    Peter - novice home machinist, modern motorcycle enthusiast.

                    Denford Viceroy 280 Synchro (11 x 24)
                    Herbert 0V adapted to R8 by 'Sir John'.
                    Monarch 10EE 1942

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                    • #11
                      How about a dust shroud for your grinder. It hooks to a shop vac. Shrouds are less than $100
                      Here is a link to Dust Buddy
                      http://dustlesstools.com/products_sh...p#.UUOlEmt5mSM
                      Sole proprietor of Acme Buggy Whips Ltd.
                      Specialty products for beating dead horses.

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                      • #12
                        First I'll state that I don't know much about aerated concrete or working with it, but I have worked with regular solid concrete several times.
                        Now, my suggestion:
                        Use a circular saw with carborundum concrete cutting blade and cut two parallel lines leaving the width of the channel you need between them (50+ mm). Use an air chisel to chisel the space between the cuts out. I've used the common automotive type chisels for this work and they work fine. If you don't mind a workout and don't have either the compressor or the air chisel you can do this by hand with a hand chisel and maul.
                        With regard to the blade I suggested, perhaps you could use a cheap carbide tipped blade designed for wood instead, given that a hacksaw blade will cut it. These blades work to cut the cement backer board used in showers and on floors before installing tile so they may work in air entrained concrete.

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                        • #13
                          Cut down an old hand saw,take the handle off and mount it on the backbone of the saw. Better yet a handle towards each end.
                          You can cut until the handles bottoms out if you want to.

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                          • #14
                            How about something like this grout tool: http://www.homedepot.com/p/t/2022229...N#.UUQAXYy9KSM

                            Or one of the vibratory tools.

                            Or with a product like rastra block, a polystyrene concrete mix, they recommend a cheap electric chainsaw that you dispose of at the end of the job. The chain saws pull out bigger chunks prone to less dust. Of course they also make chainsaws for cutting regular concrete $$$$$$$

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                            • #15
                              I have a chainsaw chain with carbide teeth. We use it for cutting up old lumber that might have nails in it that you don't see. I cut some concrete pipe with it also. The chains are not that expensive. I use it on a gas chainsaw but you could use one on an electric one I would guess.
                              How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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