kraythe

Suggestions for spanning large tips with firebrick

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Greetings, I mostly use firebricks for a forge and I am having a problem that I was hoping to get suggestions on.

I would like to create a forge that had a top that spans more than one brick but am having difficulty figuring out how to span the gap when it's longer than a single brick. The thoughts I had were.

1) put a threaded rid through bricks on their side and clamp them into one brick. The problem is that these bricks are quite fragile and I think in thermal cycling they would crack as they have nowhere to go against clamp pressure.

2) put something under them to support them. The question is of cours what could I put under them that would survive welding temps and not add a ton of thermal mass like hard bricks would.

Any suggestions on these two or another technique?

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Look at old stone/brick arches - The arches are longer than the individual stones/bricks, The arch will support itself if the sides cannot move outward. The bricks are cut in segments of the arch, and with the "Key Stone" at the top - it forms a self locking Arch that is very strong and self supporting.

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I think Jeremy has an exilent solution. The arch doesn't have to be a full 180 deg. Arch. 90 degre would be sufficient. I have shaped fire brick with an old rasp before. If you do a bit of math, you can make a jig to hold the rasp and work the edge of the brick back and forth untile they fit together. Then a simple frame to hold them in place. I'm a belts a suspenders kind of guy so a thin bit of stove cement just to fill any irregularity might be in order.

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Good thoughts so far. I'd be tempted to want to try simply casting "concrete" out of refractory, but then that's the medium I used to work with.

 

 

A friend on mine who I used to work with, did a fabulous thin shell "concrete" dome for one of our architectural structures projects in college. Poured less than 3/4" thick at the thickest point, it still supported almost 800 lbs ( we ran out of weights that would fit on his project at that point) Total weight was still under the 15 lb limit for the project.

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 In a pinch you can actually machine soft insulating fire brick on a table saw, dry.   Sawing fire bricks dry is a very dusty propisition so a good dust control system AND resptrator should be used .   A wet saw can be used but then the brick must be thourghly dried.     As I recall I used a worn out carbide wood cutting blade which was disposed of after use .  Although I have not tried to alter standard fire bricks to arch bricks I see no reason that it couln't be done.  

 

Having said this  If the arch bricks are readily available I would purchase them rather than fabricate them.  Another alternative would be to cast and fire your own insulating refractory.  I have recently seen a tutorial on this which I will attempt to relocate.  If you are near a craft school and can fire ceramic units this may be an option,

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My forge has a firebrick table.

Please take a look at attached pics.

 

Each brick is 9'' long, 4'' wide, the table is 36''x20''. The outer frame was of angle iron and every 9'' along the width I put a 2'' wide piece of steel so the firebricks would have something to rest on. In order for the table not to sag, two pieces where welded on the underside of the table in order to support the 2'' pieces. These supports ran the entire length of the table and once welded formed a 'T' with the original 2'' piece.

post-27777-0-88990800-1377110583_thumb.j

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A good place to start is the Library, there are a lot of kiln building books and a forge furnace is generally a small version. this spring I hit the library excess book sale and amongst the loot scored was, Fredrick L. Olsen's "The Kiln book" The thing has more information about kilns, materials and construction than a boy could use. For example, It lists fire brick by manufacturer, type, formula and construction, performance, etc. there are a LOT of different fire bricks available. It covers refractory blankets of all makes, kiln cements, pourable and rammable refractory mixes. Goes into kiln washes in depth.

 

The last time I was in a pottery supply they had shelves of different kiln books, second only to glazes. The "pottery" books fell to third place in the how to section.

 

Frosty The Lucky.

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