In article . com,
wrote:

of the 1/4" (0.236, actually) for

Well, 6mm actually

Hey, if it's 12" x 12", it can't be 6 mm thick smiley emoticon if you
didn't infer it already. Americans despise the metric system, because
it's based on logic, and it's too easy to work with.

I bought a pallet load of acrylic a few years ago, 4' x 8' sheets, in
nominal 1/4" and 1/2" thicknesses. I spent a week cutting it up into
pieces that were supposed to fit together, first blanking on the table
saw with the fancy plastic cutting blade, and then routing to finished
size with radiused edges. Then I found out that roughly half of the 1/4"
stuff was really 0.250, and the rest was 0.236.