The usual way to true one edge is to use a tool called a jointer. It is a type of plane. There are hand operated planes that do this work, but the most common ones are electric.

the basic idea in iperating these is that you have a long, flat, infeed table, a adjustable cutter, and an outfeed table that is even with the cutter.

Let's suppose you have a board with edge variations that you guess are up to 1/4 of an inch. For a 1x6 this would look really ratty! You set your jointer/planer to take a cut of 1/16th of an inch. As you start to feed the board the irregularities slide along the long infeed table and the end of the board hits the cutters, or rides over it. Eventually the wood that was on the infeed table is pushed enough that the cutters start to take a bit and generate some sawdust. At that point the board is now touching the outfeed table, (exactly levvel with the cutter, remember) and supported by it. You continue to push the board through, Some spots will be high and jump over the cutter, but others will get flattened out.

On the second pass you remove more of the edge variations, and by the third pass you may hear the continuous cutting of wood which tells you that the board has fed smoothly and the edge is now even.

If you take smaller cuts it will take more passes to give a perfect edge if the board is extremely bad, but with a decent looking-piece of off-the-rack lumber it only takes 2 or three passes to give a perfect edge, even with a cut of less than 1/16th or so.

You can do something similar with a table saw and some additions to your fence.
Set up your table saw to remove the variations on the edge of your wood. Try this: Get a 4 foot long 2x4. Rip 1/4 inch off one edge, then flip the board around, move the fence closer to the blade by 1/4 inch, and rip the other side. This should give you a board that is about 1 1/2 by 3 inches, with two parallel sides.

Turn the saw off. Take a yardstick, square, ruler or other straight edge and slide it against the outside edge of the sawblade (the side of the blade that is away from the fence). secure that straightedge to the table of your saw with clamps, weights or whatever. Or, use it to draw a pencil line on the table of your saw. Now lower the sawblade so it is under the table. Line up your 1 1/2 x 3 board on the line, or gently press it into contact with the straightedge. About 15 inches should be past the blade, or the slot in the tablew where the blade will come through.

Hold this board securely in place and bring the fence in to touch it. Lock the fence in place. Remove your straight edge and any clamps or other tools that are on the top of the table saw, but leave that former 2x4 in place nect to the fence.

Turn on your table saw, and carefully raise it so that it cuts through the former 2x4, then push the board through the saw to complete the cut.

You now have a onepiece jig which you can use as a fence attachment for straightning the edges of boards. When you set it back in the position it was in before you raised the blade through the wood you will see that this board is aligned exactly with the outside edge of the sawteeth.

You can also make a two piece jig by aligning a board behind the blade to math up with your line, or straightedge, and then have a second, slightly narrower board attached to your fence infront of the blade.

Now take you wobbly plank and feed it through your table saw with this jig attached. Keep even pressure against the fence both on infeed and outfeed. With the one piece jig you will remove an amount of wood equal to the kerf of the sawblade. With the two piece jig you can adjust this to as fine a point as you wish. The idea here is that your rought wood goes into the saw and after passing the blade the new edge is pressed agains that outfeed fence and is used to support the board. Once you get that established, you are simply sliding this new, straight edge along your outfeed fence, and any irregularities are cut away, or pushed away from the blade. A few passes, and anything that was pushing the board away is removed, leaving just a straight edge.

Be careful with powertools. This technique can be improved on to make it safer. I have not mentioned guards and other necessary safety components in this discussion only in order to simplify the description, not to suggest that they are not needed.

Hope this helps. And you DO like sawdust don't you?

PGJ

PGJ