Finally work as slowed down just enough that I could slip away on Tuesday (10/29) to check in at the mirror grinding workshop. I brought my blank along. I consulted about how to start, and as a result I decided I should build a box to store the mirror and tool in and, before making a tool out of dental cement, I would need to acquire a metal ring to hog the blank out before it would be ready for a standard tile/cement tool.
Regarding the “hogging tool” a down-the-street neighbor who’s a plumber offered me a toilet flange … about 7.5″ inches across with a 2.5″-inch hole in the middle. I’ll have to find out whether that’ll do from somebody who understands the hogging out stage better than I.
As for a storage box, I decided the best thing would be to design a two-tiered box that could carry both the blank and the tile/cement tool. From Home Depot I got a sheet of 24x48x7/16 OSB for $6. [OSB is cheaper by half and 10% heavier than the plywood equivalents for sale at the hardware store.] I also ordered two handles and a hinge from McMaster for $10.
The flange was a little rusty. I polished that up with a wire brush on a drill.
I built the box with an interior square of 13 7/8″ and an interior height of 5.5″. I used simple rabbets all around the rim of the bottom and top pieces and along one vertical side of each side piece. I glued the main pieces of the box together and then nailed them.
I used a scrap 1/4″ piece of plywood to serve as the dividing layer, into which I drilled four holes to make removal and replacement easier. I used scrap from the OSB to make “rests” onto which the dividing layer can sit.
I treated the OSB with … what else: BLO.