OK. Norm has confused me again!

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 centered.
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?
FoggyTown
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Just because Norm does it does not make it right. The program is a marketing machine and little else.

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Good logic. Do things incorrectly to entice people to buy more?????
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Make the mortice first, the way Norm says. Then make the tenon to fit. Don't just be too enamoured with specific bit dimensions. Similar things for dadoes.
Steve

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I agree with Steve - always make the "hole" first, then fit the item (dado, door, drawer, et al) into the hole.
RVH
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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.
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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.
--

-Mike-
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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 tight.
Anyway, I suspect he has a team of elves that do all the real work.
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LOL!!!!! A healthy cynicism is the best defense against hero worship!
FoggyTown
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Granted, but how do I prove that to SWMBO? She expects me to match him!
Maybe I better order a couple more boxes of nails...
GerryG
On Mon, 21 Feb 2005 14:58:01 -0000, "gandalf"

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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 miter).
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.

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Chuck Hoffman wrote:

Those setups but they're an essential part of the project. One of the things I like about 'Router Workshop' is that they do show the setups.
--RC
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foggytown wrote:

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.
Deb
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"foggytown" wrote in message

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 for me.
Use this method when you want to precisely center a groove in the width of your workpiece.
--
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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.

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Plow cut, I believe.
Why is it no one in the thread has commented on the oft-repeated video "test fit" he includes?
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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.

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you're missing nothing. measure right the first time.
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wondered this myself. Good job explaining the puzzle. -- Igor
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Mon, Feb 21, 2005, 6:33am (EST-3) snipped-for-privacy@aol.com (foggytown) plaintivel asks: <snip> I know I'm missing something. Can the wise heads in hereenlighten me?
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.
JOAT Intellectual brilliance is no guarantee against being dead wrong. - David Fasold
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