Jointer question

Hi all . . .
Yes, I don't know squat about jointers.
Never had a jointer before, and the only real reason I got it is because I happened on a mother load of balsa in an estate sale. It's all rough cut oversize, and I thought the jointer would be useful in cleaning up the balsa, one of these days.
It's a Delta table top. Not a 'real' jointer, I know.
Read the book (such as it is), jumped through the hoops to check the blades, and had to shim the output table so it was flat and even with the input table when the cutter is cranked down below zero.
If I lay a metal straight edge across both tables, it rests flat all along it's length. No gaps, no high spots.
I think that was ok to do.
Jointed the edge on a few balsa planks just to make sure the thing worked (I build giant scale radio controlled model aircraft).
Trying to build the David Marks torsion box to use as a building surface for major model airplane structures. The current model has a 6' fuselage, so I'm making the torsion box 30" x 6'. Anything larger will eat too much floor space in my "shop".
Got the materials (the BORG ripped the MDF to 30" for me) ready to cut.
First step is joint 2"x4"s to make a flat work surface to build the tension box _on_.
Played with a bit of scrap 2x4, and don't understand what's going on.
I ran the 2x through on 1/32" depth until the edge of the 2x was square over the length. Just playing, mind you.
Flipped the scrap 2x to the other edge and did the same thing.
Now the 2x is visibly tapered end-to-end.
I know the destructions for the torsion box say to joint one edge and rip the other parallel, and that's not the problem.
I just don't understand why the scrap 2x wound up being very obviously tapered.
Not feeding it correctly ? Failed to maintain constant down force ?
The scrap wasn't tapered before jointing, at least not that I could see. It was 'semi-ok' scrap, nothing real ugly, ordinary borgstuff.
Or, is this a normal result of jointing both edges of a piece of wood ? The nature of the beast, as it were ? Cheers, Fred McClellan the dash plumber at mindspring dot com
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Your mistake was running the opposite side of the 2x through the jointer also. The jointer is to be used to straighten and flatten 1 edge and 1 side. A thickness planer will insure against the faces of the wood tapering and the rip with the TS will insure against the taper of the edges.

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Fred McClellan wrote:

And then you raised the outfeed table, right? If not, you left both tables parallel and then raised the cutter... that would be bad. You basically have a power planer in that configuration, not a jointer.
The outfeed table, and the top of the knives, need to be slightly above the infeed table... most I've heard say 1/32" or so should be plenty, although if you are working with an easy-to-cut wood and have a lot to take off to get it straight you could probably set it at 1/16".
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On Mon, 01 Sep 2003 13:14:39 -0700, "Kevin P. Fleming"

Uh . . . maybe I didn't do a good job explaining what was wrong.
When I got the jointer, the outfeed table was not flat with respect to the infeed table when the infeed table was all the way up. I know I said "when the cutter is cranked down below zero".
Dyslexic lips, y'know. I was looking at the depth of cut scale and thinking about the cutters, not the infeed table which is what moves up and down.

It is now, except when the infeed table is cranked up to zero, above the cutters. Cheers, Fred McClellan the dash plumber at mindspring dot com
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Think about what a jointer does. It removes the high spots. Since the piece in question probably had a high spot either in the middle or both ends, you would end up with opposite sides non-parallel. Now, if you get a straight edge, scribe the opposite so you have a line parallel to your straight edge. Lay a low spot on the outfeed gently, take off the high spot following, work until the board is approximate, then run for straight, and you'll get pretty parallel.
A jointer is a motorized plane, and the techniques used are similar.

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My guess is he had a high spot in the center. There's a tendency, when the high spot is in the middle, to joint a straight line between the high point and the trailing end, and then reduce the whole length to that line. Obviously that line is not parallel to the original edge with the board.
As you suggest, drawing a line to find the high spot, and then working that down first, is a good plan. For some reason, that's an intuitive thing when using a hand plane, working the high spots first.
John
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I teach it every year when new kids come in. Simply sighting the board is usually enough to flag high spots for the first pass. If only there were some way to do the job without having to retract the guard manually!

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Well, there is the good ol' jack plane. I'll often take a few swipes with a hand plane to get an obstinately shaped board ready for power-jointing.
John
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Thanks for the info folks.
Think I got it.
The jointer is doing exactly what it is supposed to do - make one edge and one face flat.
The other edge has to be ripped, and the other face has to be planed.
The task at hand only needs the two edges flat; the faces are a don't care. The jointer and itty TS are enough for now.
When the model airplane building budget allows I may get a power planer, but right now landing gear retract systems eat bucks to the tune of $650 a set, and I've got three giant models waiting for the building table.
BTW - I once read 'Seven rules for squaring a board'. Don't recall if it was here or in the Yahoo lair. Anyone seen that little tid-bit ? Cheers, Fred McClellan the dash plumber at mindspring dot com
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Right.
Right again.

It's not accurate to say that you don't care about the faces.
First off, unless you have made a face straight and flat *first*, you have no guarantee that the edge you joint is straight and flat. If the board does not have a straight, flat face to reference against the jointer fence, then edge-jointing it can (and probably will) produce a twisted edge.
Also, you need to have one face straight and flat before you run the board through the table saw. Otherwise, the edges may not be parallel in all dimensions. For example, if the board is cupped, you may have edges that are parallel along the length of the board, but not across the width.
The proper procedure is to joint one face straight and flat, then joint one edge square to that face, then rip the opposite edge parallel. The final step in squaring a board is to plane the other face parallel to the jointed face. It appears from what you said that you don't need this step -- but you *do* need *all* of the other three.
-- Regards, Doug Miller (alphageek-at-milmac-dot-com)
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Nope, but if the user wants, he can use it to make it so.

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Yes, and he/she can make it so with a sharp rock if they want to badly enough. I've done it myself (with a jointer that is, not a sharp rock) but I'm only addressing the designed use of a jointer and the posters question.
However, if you have to make a comment, make it useful rather then a useless noise on an obscure and complicated point. Describe how one goes about accurately making two edges or faces parallel using a jointer.
--
Mike G.
Heirloom Woods
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SNIP Now, if you get a straight edge, scribe the opposite so you have a line parallel to your straight edge. Lay a low spot on the outfeed gently, take off the high spot following, work until the board is approximate, then run for straight, and you'll get pretty parallel.
A jointer is a motorized plane, and the techniques used are similar.
Cut and past from a previous message in the thread. Just how do you figure they made boards before dedicated thickness planers?

useless
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Yes, it's just a cut and paste. Got tired of recreating it every other week.
Take care Mike
--
Mike G.
Heirloom Woods
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This is normal. There is nothing for the second side to reference from. Why would it be parallel to the first side?

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