>Scenario: take a board 5' in length, 2" wide by 1" thick. The board is crooked 1/4" and bowed 1/8" over its length, with a bit of a twist.
The survey question is, how would you plane this into a 1 1/2" by 3/4" straight and flat board? Tools, setup, etc., machine and hand tools are all valid.
I'm mostly interested in how you hold the board steady for the job, keeping in mind that the board will flex if not supported, jeopardizing your work...
I don't want to sound flip, but does the board need to remain 5 foot long, or will it be used in a smaller subassemblies? If it is used in smaller parts, it would first be sawn into the parts.
I cannot imagine a board of those dimensions being used its entire length, nor would I select a board that close to my final size with those defects.
Also, it matters where the defects actually occur.
I would use what I've got to turn your crooked, bowed, twisted board into the straight, flat board you've specified.
So for me, the task could/would involve a scrub plane set for light cuts, a #5 jack set for heavy cuts and #7 jointer set for light cuts, my flat benchtop with a batten clamped to it and a bench dog (made of oak and square, of course!) popped through one of the holes at the left end. The board wouldn't need to be "held" so much as simply "positioned" for planing against the dog and batten.
In reality, I'd probably find a straighter board in the first instance rather than mess about with the one you've described. The twisted bowed, crooked board you describe would likely be better used for shorter parts.
>The task you describe is something I do regularly at my job. Here's how I would go about it:
1. Go to the jointer and set the depth at about 1/16". With the convex face of the board down, I'd retract the guard so that I could set the leading edge of the board on the outfeed table to start the cut. Because of the twist, only one side of the leading edge would touch the table. Using a push block, I'd put pressure on the center of the board and make sure the center part of the board was held flat to both the infeed and outfeed tables. As the board passed over the cutterhead I'd keep pressure on the outfeed table and let the trailing end of the board remain in the air. Most likely it would be necessary to make a second or third pass across the jointer using the same procedure. When the surface was mostly flat, with only small triangular areas at opposite sides of each end remaining from the twist, I'd take a shallow pass keeping pressure on the infeed table. The resulting flat surface would leave equal thickness at each end of the board.
2. Put the board through the planer until the entire upper surface had been machined. Because the center part of the board is thinnest and has only a small amount of wood removed, the overall shape of the board will not change significantly even if there is tension in the wood. This is the advantage of removing stock from the convex face first. Removing stock from the ends of the concave side as a first step means that the planer will remove a significant amount of wood from the center of the board, most likely causing the originally flat side to curve due to release of tension in the wood.
3. With the board now straight and having two parallel faces, I�d joint off the center of the convex edge as in step 1, then plane the second edge to be parallel to it.
If I had to do the same operation using hand tools, I�d clamp the board in the tail vise of my workbench and put shims under the center part so that it wouldn�t flex under the pressure of the plane. Using winding sticks to check for twist and a marking gauge to show how far to plane on the second face, I�d get the faces straight and parallel. Then it would be on to the face vise to remove the bow from the convex side, then mark and plane the second edge parallel.
>Personally I'd put it in the junk pile it's bound to twist up more if used for furniture. If you really intent on straightening it you'll need a long straight edge make the high spots and if there's quite a bit I'd start with a draw knife then on a narrow board like that it would be using the jack plane with a cambered blade. After you get 2 sides square then scribe and plane the next side and so on. You'll need a pretty flat surface to plane something that thin on.
>If you want to work quickly with hand tools, the first thing is to avoid lumber that is shaped like a corkscrew. Even if you can flatten it, it is going to want to move back to that shape anyway.
If the lumber isn't quite so crazy, the second thing to ask is, do I really need to 4-square this? I avoid spending any time going thru the motions of 4 sqaureing a board as often as I can. For example, table aprons almost never need to be a specific thickness or even flat on the inside. If you can get the best face flat, you are done. Some parts require a square edge to that face, but often only one edge needs to be dead square, the other I eyeball.
As for holding the lumber. Plane stop and a holdfast with a batten is all I use.
>I agree with others. There is a lot of good wood in the pond. I'd set this one free and go fishing again. The board you describe is a trouble maker! ;-)
>That board isn't all that bad, if it worked for me, I would use it. I would first section into smaller pieces if necesary, and then do what Steve Elliot said jointer wise. My other option would be to snap a line with my Japanese chalk line, and then bandsaw the convex sides. Since this board is not that stiff for it's length, I would prefer the saw.
If I was doing it by hand, I would snap a like and hew it, or just go after it with scrub plane, and a Jack plane, I don't use a Jointer unless I'm jointing. I'd like to own a fore plane, it's in process. But my basic approach these days is to mark the lines on and just cut to the lines. Since there aren't a lot of ups and downs, I don't see the advantage of a long plane (I wouldn't even if there were, but I've failed to convince on that argument before). If you have a flat surface, you can also use a guide block and pencil to mark a straight line.
