#11  
Old 10-10-2009, 01:22 PM
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Join Date: Jun 2009
Location: minnesota, usa
Posts: 472
Default Re: More efficient brick cuts

don't throw out the 'indespensible tool' option just because you don't weld. I cobbled one together with basic hardware store stuff and a few misc. pieces of junk from my garage...no welding and no special order parts required. My materials list included threaded rod and connectors, a 2" wide angle bracket, a couple of nuts, a door hinge and some epoxy. I coudn't find a lazy susan or chair swivel so I had to pin together two pieces of thin scrap wood to do act as that.
here it is covered with crap, post build. I'd offer to send it to you but I built a 36" oven so it's the wrong lenght and I'm sure it would never come apart since the rod is expoxied (and now mortared) in place.


in the first photo, you can barely see the locating pin in the wood that made the lazy susan bit. I just located that peg (it was shelf peg from a cabinet) in another piece of wood and made sure to place that dead center on my oven floor. The hardest part was getting the threaded rod connector attatched precisely on the hinge so that the angle and the sweep were spot on center. Looks like crap, worked just great and cost like $5.
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  #12  
Old 10-11-2009, 07:15 AM
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Location: Concord, Ontario, Canada
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Default Re: More efficient brick cuts

OK - so I understand now (thanks Lars) the cutting of each brick, in order to go around to complete one chain...(and I'm definitely going to use the alternating spiral method you described in the 'tapering bricks with a chisel' post) I like the idea of having the bricks held by more than just my ability to properly apply mortar...

But what about the angle required to rise from chain to chain?

I've read the posts where they use cardboard and draw out the dome shape and then place the bricks around the "dome" to get the angle (and they recommend cutting wooden wedges to that angle - to be used from chain to chain as the dome rises)
If I use a form, or become convinced by Splatgirl's explanation of how "possible" an indispensable tool is to make - then where do I get my angle from? (I'm talking about the angle on the outside of the dome, that each brick chain has to be raised in order to close the dome)...
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  #13  
Old 10-11-2009, 07:32 AM
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Default Re: More efficient brick cuts

Majic,
Okay. To get your rings of bricks ( chains) to meet at the middle at the top of the dome, the outside edge of each brick has to be elevated.

For my 39" diameter oven, it was ( via math and CAD) around 9/16" at the very edge. However, I wanted to use a little 1 1/2" square of wood ( cut to the proper thickness) as a spacer. ( even with the 'indispensable' tool you will need a spacer...I guess that name is not true because I did not use one) Since I knew I would have to jam that spacer into the bricks, I cut a whole bunch of them 1/2" thick. As you mortar each chain, you butter up a wedge of mortar on the previous chain and the last brick face, then lay the new brick on there and squeeze out the mortar until the 'spacer block' gets clamped. By the time it falls out or you knock it out, the mortar is firm.

If you calculate pretty closely, the distance you need, the dome forms kind of automatically. Mine is not perfect, I know, but it's pretty close. ( lots of pictures posted on my profile, BTW)

Lars.
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  #14  
Old 10-11-2009, 07:45 AM
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Default Re: More efficient brick cuts

Lars - thanks for the quick response (and for making it detailed enough I can understand it)
My math isn't up to it, and I'm planning a 42" oven, so I guess I'll have to use the cardboard on the floor mockup to get my wedge measurement...
I should just be able to take the measurement of the wedge that I get from my mock-up, and then taper each brick "top" surface that distance, and reduce the amount of mortar required...
So - strictly to explain my thoughts aloud - and using your measurements - if I needed a 1/2" spacer, then I could cut my brick to be 2.5" on the outside of the dome and tapering to 2" on the inside.
If this will work, then I think I can deal with it, and I have somewhere to start....
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  #15  
Old 10-11-2009, 07:59 AM
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Default Re: More efficient brick cuts

Majic..
Unless you buy tapered bricks, there are very few builders on this forum who would go to the extreme of tapering the bricks on the top and bottom of each brick!

What kind of mortar are you planning to use?

There are six faces on every brick, lets call them ( front [oven inside], back[oven outside], top [toward the dome], bottom[toward the base] and sides [ abutting the ajacent bricks in each chain].

If you cut each firebrick at an angle, you get a taper in one dimension. This is plenty for the first 8 chains. If you then do a compound angle for that cut, or shape the 'sides' you will be tapered in two dimensions. Very few have needed to do more than this.

Lars.
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  #16  
Old 10-11-2009, 08:13 AM
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Default Re: More efficient brick cuts

I have already bought the bricks and they are 9"x 4 1/2"x 2.5". I didn't purchase any tapered bricks.

What my thoughts were - I cut the 9" length as you described creating two halves (being 5" on what will become the outside and 4" on the inside). That will take me around the chain horizontally.
Then to get the vertical rise, replacing the wedge with a tapered brick... I cut the 2.5" of each half brick, so that I have 2.5" on the outside and 2" on the inside.(example only - not actual measurements)
I don't plan on cutting or shaping the sides, other than to get the 4"/5" split.
I only see it as one extra cut on the top surface. What am I missing here?
Majic31
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  #17  
Old 10-11-2009, 08:40 AM
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Default Re: More efficient brick cuts

with the indispensible tool, or at least with my version of it, the angle bracket provides the proper elevation/angle for the brick. When the top face of the brick is flush with the top surface of the angle bracket, the angle is correct. I would just put the cut brick against the bracket and set it into place in the chain, and then stuff mortar into the gap at the back until it was held in place flush with the top face of the bracket. Some people use clamps to hold the brick in the bracket, but I found that unnecessary because the brick stayed put immediately if my mortar was nice and stiff.
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  #18  
Old 10-11-2009, 09:06 AM
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Default Re: More efficient brick cuts

Majic31: I'm not sure if I understand your description. Bottom line is that it is very difficult to taper a brick "across" the face because the 10" brick saws most FB users have don't cut 4.5" deep, which would be required to cut through the brick from the edge.

Not that I would know. I haven't cut a single brick yet...but the geometry is pretty easy to conceptualize.

One thing I am considering, only for my entry arch mind you, is shaving a brick down from 4.5" to 3" wide and then tapering "across" the face because a 10" blade will reach 3". For reasons of my arch design whose details aren't important here, the much easier alternative of tapering my arch bricks on the standard 2.5" axis is less feasible.
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  #19  
Old 10-11-2009, 09:54 AM
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Default Re: More efficient brick cuts

Kebwi - thank you for the info - you have understood exactly what I thought I'd be doing.... I have the same 10" HF bricksaw you mention, and was unaware it wouldn't cut 4.5"
(I thought 10" blade - must cut almost half the radius - 5" right?). I just went out to the garage and the PVC tray is only 3" deep... so there goes that idea..
Looks like I'm either cutting wedges or attempting to build an indispensible tool to get my lift angles....
Splatgirl - I understand what you're saying, and I'm giving it serious thought..thanks
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  #20  
Old 10-11-2009, 09:59 AM
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Default Re: More efficient brick cuts

You have to account for a saw blade's "axle", which would have to be of infinitely small diameter to cut as deep as the blade's radius. I believe this is sometimes referred to as the blade's "arbor". Therefore, a blade's cut-depth is always less than the radius, for the same reason that a vehicle's ground clearance is always less than the wheel's radius.
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