the closest I can come to 1/2" BB, is 12 MM. Are you sure you are
getting BB that is exactly ONE HALF inch thick?

Dave

No, but I understand (since like weeks ago) this is one thing you can say
about Baltic Birch.

BB is always singled out. For plys, thickness, strength. It comes from one
place and/or one source.

|12mm| is less than |1/2"| by about 14 thou. I always remember that one
1/32" is approximately 1/33". 32s or 33s, who cares. And I know 1/33
divided by 1/33 is .99999... (1.0000...). So a 1/32" (1/33") descrimination
is like .033..."

14 thou is less than one half of 1/32". Less than a 1/64". Actually it is
1/7257143152"

Pretty good size, but will it fit? Maybe for a bottom. A 3-ring piece of
paper is about 3 thou. Five pieces may just hold the weight of itself from
falling out. I bet you the entire combined tolerance of the 75, 000
thousand machined parts in a Stealth fighter is less than that.

I haven't measured any sheets. I bet they are all different from each
other. Freud has an undersized plywood bit of 15/32". Infinity 31/64".
One guy said to use a sharpening service and a 1/2".

I love going to Home Depot and determining if you'll have to reverse
engineer your project when some guy sets your cut once on the wrong line.
He tells you if you're cutting an 8 foot long piece of ply four times
combined it's gonna be off by the thickness of the material. You ask, and
he says no problem. So he takes the first cut, lays out the tape measure and
exclaims PERFECT. Perfectly closer to the next closest line. Thats a buck.
Do you want the next fifteen?

I figured the panel saw out. For cutting horizontally there are two
platforms, and two reference rules. The rules don't move. One is to the
lower rest, the other to the upper rest, depending on the width of the sheet
and convenience. Absolute dimentions from bottom to top. No adding or
subtracting. No factoring in the blade. Because of gravity I draw all my
rips from bottom to top. The machine isn't set to measure the other way.
Maybe some employees would assume a perfect 48" and subtract if a drawing is
made that way. All dimensions should be contiguous, not combined, because
the top piece is removed after each cut. The thickness of the blade is zero
set. The rule never moves. 1/8" is set when the machine is built. That
is, with the needle pointer at 15-15/16", thats what you get. If you were
resting on the lower platform, say 30" away, use the other rule. It is
offset by 30" It would read 15-15/16", The machine cuts straight as an
arrow and perfectly normal.
With vertical cuts, the blade is slid over to a lock position and rides up
and down. The wood is slid side to side to a stop block. Accuracy of
consecutive cuts just depends on moving the wood over to lightly touch the
stop block. The rule for the stop block starts at zero and works both ways.
The blade is accounted for, the rules origins start .250" appart (two 1/8"
saw kerfs). The stop block is a steel fixture with a cam clamp that rides
on a rail. It is a bit figetty, but done firmly and right its all over.
The V and H rules are the same. and the indicating pointers are the same.
There is no paralax error to worry about. Pointer to rule is a fractions of
a millimeter. White steel rule with black graduations. Black spring steel
pointers. There is no operational errror introduced.