Fortunately, the refractory industry makes arch bricks in #1 and #2 angles. In combination, these two pre-shaped bricks will form any size diameter oven dome. The bricks, like standard fire brick, are 4.5" wide, 9" long, and tapered.
|Accurate bricks make a perfectly round dome|
The second aid in cutting accurate dome are the styrofoam dome forms I purchased. These allow me to set the cut bricks in rings in order to check the accuracy of the cuts. After pre-fitting the dome brick this way, I number and box the bricks for transport to the oven project site.
|Roman cross keystone TBO method|
I built my first oven from Internet plans, with some modifications.
Cutting fire brick is an essential aspect for building domed brick ovens.
I currently use a Rigid brand sliding compound 12" miter saw mounted on a rolling workbench (Rigid brand too). It is portable so I can take it to project sites and cut custom shapes when needed.
It is the best of the saws I have used but not absolutely necessary. My first oven was built with a simple Delta chop saw (but this took some mechanical acrobatics in order to get angles and the blade was 7' which was not always wide enough to complete cuts in one pass). Next, I used an old Craftsman 10" radial arm saw (not a very strong motor but I could run a hose to spray the brick while cutting and speed the cuts).
Now I soak the bricks and cut them wet with either the Rigid or a commercial block, stone, and brick saw.
Cutting angles for each brick on each 'chain' or band on the dome becomes pretty obvious as you go. Note that there are two important angles. The Wedge shape (as viewed from above) and the Skew as view from the end. Since my goal was to eliminate internal gaps these two angles were most important (structurally too). The third angle (call it the Taper) is the formed so that the outside of the dome is tight. I wouldn't recommend this for a one-off oven as it involves a ton more cuts. In the past I have saved wedges from other cuts to fill behind the bricks so that the dome shape is formed. Or I used wooden wedges as temporary spacers until the rest of the mortar set up.
Now, I cut sufficient bricks for a number of ovens, setting the angles on the saw and proceeding in the most efficient way to produce the 300 or so pieces needed for a 42" dome.