One of the design decisions that I made while thinking about this
process was that I wanted the outside of the kiln to be cylindrical
not polygonal. I wanted the tensioning of the steel to apply equal
pressure everywhere, and I didn't want the fibre to be compressed at
the corners. So, I had to grind the back of the bricks down in an
appropriate portion of a circle. I decided to do this with my table
saw.
The first step is to construct a jig. The jig consists of a single piece of MDF with two stops on it. The two stops are for the hot face of a brick, and one of the sides. The whole thing is nailed to my work bench through a drilled out hole. This way the jig can slide back and forth in an arc. It is nailed such that when a brick is in the jig and the position is top dead centre the brick just touches the grinding disk. (Which in my case was 23.25 + 4.5 inches.) In the picture you can see that I put on a hold down clamp, and some sand paper so that I didn't actually have to hold the brick.
Here's a brick about to be ground. I used an 8 inch masonary disk, it
goes through the IFB like butter, but does produce a lot of dust. If I
had been thinking I would have put a rubbermaid under the saw to catch
dust and IFB chunks. There is a lot of dust produced in this process,
so taking some time and setting up good dust collection is very
recommended.
Unfortunately, my saw being 8 inch couldn't expose enough of the disk
for me to do it in one pass. That's why you see those unsightly
grooves in the bricks. Either my swing arm wasn't perfectly square and
centered with the arbor, or I wasn't placing the bricks accurately
enough. It doesn't really matter anyways, the fibre will fit now very
well against the IFB.
After grinding all the bricks I mocked up two courses of the kiln again.
