Flat/square boards with only a jointer?
I’m still in the learning process of woodworking, having done a lot of reading but not yet committed to buying machinery or tools just yet. There’s one thing that I can’t seem to figure out. After reading a lot on jointers vs. planers, it seems to me that the accepted wisdom is that you need both to make a flat, square, and parallel board. However, it seems to me that a jointer can do two things: make a face of a board flat, and flatten an adjoining face to 90 degrees.
The usual rationale for a planer is that a jointer can’t make two opposing sides parallel.
So why can’t you take a board, joint one face, then flatten the edges adjoining the flattened face, which should give you 3 faces of the board that are flat and 90 degrees to each other, and then use those edges to reference flattening the fourth face of the board? If I learned anything from geometry, it was that four 90 degree angles gave you a rectangle.
Please tell me where my reasoning is flawed. I’m sure it’s flawed someplace.
Replies
What you suggest would work in theory, but it would be very difficult or impossible in practice. When edge jointing, you reference the nice wide, flat face of the board against the fence, producing a flat edge perpendicular to the face.
However, to produce a face perpendicular to the edge, you would have only the very narrow edge referenced against the fence. It would be very difficult to keep the narrow edge perfectly flat against the fence; most likely, the board would rock slightly, producing a not-very-flat and not-very-square face.
Your one face and 2 edges logic is sound. But when you try to do the opposite face, in theory you should get one that's 90 degs to the edge against the fence, but you've got no real control other than your hand pressure in terms of how much you're taking off that face. That's one way that the faces don't come out parallel and that's assuming the face your jointing is fairly flat to start with. If that face isn't so flat, the problem is even worse.
The other difficulty is in the amount of material that's up against the fence. It's a lot easier to keep the face of the board against the fence as you do the 2 edges. The weight of the board alone plus the much narrower bearing surfaces against the fence mean it's a lot harder to use an edge as a reference for jointing the face. There's no real good way to hold it and keep the edge up against the fence while at the same time keeping all of your fingers attached. If you could effectively do all that, you're right - 4 90's will give you a rectangle - but the depth control problem means your rectangle could taper or vary in thickness through the length of the board.
If you build it - he will come.
The other posts have listed the difficulties with doing what you suggest.
Your question basically is one of trying to get your lumber squared up by using one less tool. I would suggest that this is possible if you use a planer and a table saw ... no need for a jointer. In fact, I have no jointer and make some really nice furniture and the like.
I first start by running a board (rough) through the planer to flatten one face. I use a sled and if the board wobbles on the sled I use wedges and the like to make sure that it lies absolutely flat. Take very light passes and the face will become very flat. Before this face is totally planed (rough saw marks removed), turn it over and plane the reverse face. This face will be parallel to the first one. Continue planing the two faces until you are satisfied with the result.
Now, take the board to the table saw and, using a long jig, straightline one edge. My jig is a very straight 2X4, about 8 feet long, with a piece of 1/4" hardboard glued to the bottom, My board rides on the hardboard, with the edge against the 2X4. I put the edge against the 2X4 that creates the least movement in the board I'm trying to straightline. Another way to straightline a board is to build a jig and use a router.
Once you've got one straight edge, it's a piece of cake to place that edge against the fence and create an opposing straight edge.
John
The problem is where the theory runs into reality.
You can flatten one face of the board and square up the two edges, but how would you then hold the narrow edge of the board tight enough against the fence to keep the wide face of the board reliably square to the fence while you surfaced the fourth side?
The second problem is that even if you could hold the board tight enough against the fence, this still wouldn't guarantee that the stock would come out even in thickness. You can make a board with all four edges and faces square to each other but the board could still taper in length. This is done intentionally with tapered legs for instance.
As nice as it would be to not need both tools, you will need both.
John W.
You can get close. Plenty of people have used the jointer as a proxy for a planer from time to time. It's not a long range solution. Save up for a planer.
For the first five years of my woodworking career ( now 25 yrs ) I did not have a jointer. Where you theory is flawed is in skipping the tablesaw before you joint the third and fourth face. First joint one face and one edge then saw the second edge parallel to the first with the jointed sid edown. The next step is to resaw the board to the desired thickness plus the amount you jointer will remove. The trick to the tablesaw is to tilt your blade at about 2 degrees when resawing the thickness of the board, sawing up half way on each board. When you return to the jointer the fourth face will slide on 2 edges with the center not in contact with the jointer table because of the 2 degree tilt.
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