wooden-furniturewoodworking
I'm joining 4 rough-cut boards together to make a work table. There's about an inch of variation in width on each side of the board, so I have to plane the sides before gluing them together.
How can I get a base "straight" line to plane against when both sides of the board are crooked? Ideally the 4 boards would plane down to straight sides, so the resulting joined surface also has straight sides.
Yeah, that 4" would be a long cut. It could be done in two passes, one from each side. The middle area would have a bit of an overlap and maybe a blade mark, but that could be sanded down. Plus you are probably going to finish it anyways.
What I would recommend though is changing the shape of your transition piece to make it easier to cut, and would also make it more pleasant to walk ok. I posted a similar question regarding a transition from tile to hardwood. Although your question is different, some of the answers there might help you out. For example, take a look at the shape of this transition piece:
In your case, this would be 3 separate cuts instead of one long one. Also the flat top surface will make it more pleasant to walk on vs. the angle (point) you have at the top of your example.
Could you do it... Yes. There are a few problems with this setup.
First, if the saw does not have a locking trigger how will you turn it on when you are cutting? If it does have a locking trigger, you'll want a way to turn the tool on/off quickly and easily. This could be achieved by connecting the saw to a power strip, and mounting the strip in an easily accessible area. You'd then use the switch on the power strip to turn the saw on/off.
Will mounting the saw make changing the blade difficult/impossible?
Mounting a jigsaw in this way could make it easier to force the wood, which could lead to binding, flexing, and even cause the blade to break (which could be deadly).
Lastly, why are you using a jigsaw for long straight cuts? Long straight cuts are far easier with a table/circular saw. The great thing about a jigsaw, is that the blade can bend and flex slightly. This makes cutting contours easier, but will make long straight cuts more difficult.
Best Answer
What you are wanting to do would be better on a tablesaw because of the amount of material to remove. A Jointer or Planer is good for making very strait edges and tight joints, but with 1/2" of variation, you're not to that point yet.
What you want to do is a form of a "tapering cut" on a table saw, but instead of tapering, you just want to make the edge straight. Tapering is when you have a board that is 6' long, and the top needs to be 3" wide and the bottom needs to be 4" to make up for a crooked wall or similar.
http://www.finehomebuilding.com/2014/09/25/how-to-cut-a-tapered-board-on-a-tablesaw
There are many videos and how to's if you search for making a tapered cut, and they usually involve attaching your board to a straight board at an angle. You'll do the same thing, but without the angle.
I've done this with boards as long as 8' and a taper of 1/2" or so relatively easily.