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Pre-Construction Questions - Forno Bravo Forum: The Wood-Fired Oven Community

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  • #16
    Dutchmen everywhere .. some with questions

    Hi Guys,

    James: with regards to the $25,000 pizza oven: I'll take a picture of it and post it on here.
    And yes: I'd be more than happy to refer your products to people here - hell, I could become your NZ representative... but then again, total population of NZ is only about 4 million, so that is a pretty small market. And Kiwis are inveterate Do It Yourselfers. (supposedly a Kiwi can fix anything with a piece of no.8 wire)

    There are indeed a lot of Dutchmen here. The bulk of them came after the second world war. I came here 25 years ago, chasing a kiwi skirt...

    And there are lots of Dutchmen everywhere, including the US. Hey: New York used to be "New Amsterdam" you know...

    Marcel: My *real* name is actually Peter. (not that I mind a helluva lot.. )

    Now for some more questions:

    I went and saw my fire brick supplier about the type of bricks I am getting. They are 9" X 4.5" X 3" with about 37% Alumina content, so should be good, from a thermal point of view.

    He suggested I shouldn't be using refractory mortar between the bricks, but rather refractory concrete ("castable"). He reckons mortar is only good for gaps between bricks of a 4-5 mm. (just over 1/4 inch) Because the bricks are going to angled on both the horizontal plane as well the vertical, the gaps will be (much) wider than that.


    Also he reckoned I would not be able to cut the bricks with a skill saw with a diamond blade, because they are way to hard. He would allow me to use his big industrial saw to cut them, but at a cost of $1.50 per cut... !!! (Dutchman getting very sensitive now )

    Is it really that hard to cut firebricks?

    Anyway, I am going to be buying a grinder with a diamond blade, and see for myself...

    Comment


    • #17
      Originally posted by KiwiPete
      Also he reckoned I would not be able to cut the bricks with a skill saw with a diamond blade, because they are way to hard. He would allow me to use his big industrial saw to cut them, but at a cost of $1.50 per cut... !!! (Dutchman getting very sensitive now )

      Is it really that hard to cut firebricks?

      Anyway, I am going to be buying a grinder with a diamond blade, and see for myself...

      It's easy to cut, but you WILL burn through the blades. We cut every brick more than we needed to trying to get better angles and even mounted on a wet saw (tile), we burned almost through one blade. Dry cuts will make SURE you burn though the blades and you will raise enought dust to make all the mortar you require... assuming you could collect it (we did from the water bath under the tile saw).
      --
      Tarik

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      • #18
        Everything is relative: firebricks are harder than common red brick to cut, but with modern sintered diamond blades, you can cut them easily. Fire brick is not nearly as hard as granite, say.

        There are a few basic ways to cut brick. The cheapest good way to do it is with a 7" tile saw, that works like a table saw with the blade running in a tank of water. This won't cut all the way through but you can make a second cut, or break the brick cleanly at the cut. The bad news is that this sort of saw throws up mud into your face. The good news is that they are really cheap.

        A ten inch masonry saw has a bigger blade and a more powerful motor. The blade is fixed above the work, which is carried on a rolling table underneath. It has a pump that keeps the blade wet. This saw can cut a brick in one pass. This is a professional machine that that can cut masonry all day.

        Some people dry cut bricks with a segmented dry blade in a skill saw. This seems bad for the lungs and the saw to me.

        There are also people who break the bricks with a wide chisel called a brick set. This is not a skill that I have ever been able to acquire, but that doesn't mean that it can't be done.

        Real refractory mortar is expensive (and nice to work with - I've used a brand called heat-stop here in the states). The pompeii instructions call for a fireclay-portland cement mixture, which seems to work fine - I think real refractory products don't have portland cement in them.

        Good luck with your project.
        My geodesic oven project: part 1, part 2

        Comment


        • #19
          Originally posted by dmun
          Everything is relative: firebricks are harder than common red brick to cut, but with modern sintered diamond blades, you can cut them easily. Fire brick is not nearly as hard as granite, say.
          Yes, indeed. Or concrete.

          A ten inch masonry saw has a bigger blade and a more powerful motor. The blade is fixed above the work, which is carried on a rolling table underneath. It has a pump that keeps the blade wet. This saw can cut a brick in one pass. This is a professional machine that that can cut masonry all day.
          This is what I used, and believe me, we cut all day for 3 days. But then we cut every single brick at least 5 times, trying to get a better fit.

          If I'd done the math for the horizontal curve of the dome, I would have been able to darn near dry fit everything. Instead, we ended up with a tight fit at the outside with gapping on the inside as the taper was too extreme.

          Some people dry cut bricks with a segmented dry blade in a skill saw. This seems bad for the lungs and the saw to me.
          Face mask. Mandatory, IMO. Just cutting a few bricks this way with my grinder generated a LOT of dust.

          There are also people who break the bricks with a wide chisel called a brick set. This is not a skill that I have ever been able to acquire, but that doesn't mean that it can't be done.
          I have been able to develop some skill at this, but it is definitely a challenge. You need to work around all surfaces just the right amount to develop fractures within the structure to get a nice clean break. It seems easier (to me) with larger blocks than smaller ones.

          Regards,
          --
          Tarik

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