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?
It would make sense if you can control the thickness of whatever fits in the
dado slot. You can later make a tongue on the mating part to fit perfectly
and use the same technique to center it. OTOH, if you are fitting a piece
of plywood, you end up with a centered dado and sloppy fit.
Correct. But if you start with a setup that's something too small - say
it's a 1/2" setup for a 3/4" plow - then by setting the correct distance
from the edge of the board to the fence and doing it Norm's way will give
you a perfectly centered dado of the proper width.
Norm can be both idol and demented bodger in the same show. The more I watch
the less impressed I get. His passion for his nail-gun drives me nuts. So I
suppose it doesn't matter how sloppy his joints are as 50 nails will hold it
Anyway, I suspect he has a team of elves that do all the real work.
This is, after all, a TV program that condenses one or two days' effort into
a half hour program. They don't show setups, mistakes (and the resulting
rework) and the time-consuming but not very interesting detail work. They
also don't show the hand-fitting of joints (except for the occasional
But you can be sure that what you see on NYW is not the whole story. All
tenons don't fit their slots perfectly the first time, every time.
I am not a "Normite," but as Edwin said, it makes a difference "why" you are
cutting the dado. If it is for a tenon, then it really does not matter how
wide (within limits) the dado is because you are going to fit a tenon to
the finished dado. On the other hand, if it is for fitting a board into
the dado, Norm would be the last to advocate the double run. You do a lot
of trial and error and HOPE all the boards are the same thickness.
Easier to do than explain.
Set the fence so that the first pass is _slightly_ off center in a piece of
scrap PRECISELY the same width as your workpiece. Flip the board around and
run it through again. Now tweak the fence setting until the two successive
passes cut the desired width. Same with router bit or dado stack.
You obviously need the blade, bit, or dado stack to be narrower than the
desired width of your groove ... half, or a rch more than half, works well
Use this method when you want to precisely center a groove in the width of
Even the most experienced woodworkers will run a test piece to make
sure the groove will fit properly, and small adjustments will usually
be made. It makes sense to plan for having these (important) test
pieces when cutting your stock and they may be needed for testing
finishes anyway. Not always, but I usually cut grooves before the
tenons/tongues. For a better understanding, a groove is cut with the
grain, a dado is cut across the grain.
You do not use the correct size dado set up to start with. You take out may
be 2/3's on the initial first pass and then flip the board. Also you should
make the grove purposely small so that you can sneak up on the perfect cut.
I use this technique all the time.
Mon, Feb 21, 2005, 6:33am (EST-3) email@example.com (foggytown)
<snip> I know I'm missing something. Can the wise heads in here
Very simple answer, surprised you haven't figured it out.
A bunch of us here got totether, and petitioned Norm to do it that
way, just to confuse you. He was nice enough to oblige.
Intellectual brilliance is no guarantee against being dead wrong.
- David Fasold
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