I sit in thunderstruck adoration watching "Nahm" make some pretty good
stuff and I do learn technique and technical points from him as well.
Sometimes, however, there are things he does which just "don't compute"
as they say.
Frinstance: when making dados or other deep grooves in stock, he
always recommends to run it over the blade/bit twice - first with one
face towards the fence and then with the opposite face towards the
fence. That way you are sure that the groove/slot/dado is perfectly
OK. I understand that well enough. BUT . . . if the blade/bit isn't
perfectly centered to begin with then the initial cut is going to be
off-center (one way or the other) which means that the second cut is
going to be again off-center but to the opposite side. This means that
the groove will be too wide by twice the factor of the original
off-centering. Say you want a 1/2" dado and the first pass is 1/32 off
center. The second will add another 1/32 which means the groove will
be 1/16" too wide.
All this tells me is that you're going to end up with a perfectly
centered dado but also a sloppy panel fitting (especially if they are
floating to begin with) because the slot is too wide.
I know I'm missing something. Can the wise heads in here enlighten me?