Straight Edge Options

Jointer bed too short to handle that long piece? Here's a grab bag of jigs, rigs, and tricks for making long straight edges. July 21, 2005

I am wondering what everyone uses for a long straight edge? I need to do a few 8-10 feet glue-ups, and my jointer bed isn't long enough to handle these well. This is only an occasional need for me, so I don't mind clamping and routing, but I'm not sure what’s the best thing to use for a straight edge. It needs to be stiff enough to rout against without flexing. I'm wondering about an aluminum extrusion, but I'm not sure how straight these are made? I tried an aluminum angle in the past, but it flexed. Any ideas are appreciated.

Forum Responses
(Cabinetmaking Forum)
From contributor S:
How big is your jointer? If at all possible construct a temporary in feed and out feed to your jointer. It doesn't take that long to make one, and if you spend a little time designing it and building it you can store it in your shop for future use. We have a large 16" jointer, but the bed is only 7' long. We occasionally mill long stock (over 16') and use a shop built in feed and out feed system.

It works great, but did take probably two-three hours to make. We made ours so it can be clamped to the jointer and it has adjustable legs to account for the floor being out of parallel and the depth of cut. We just used adjustable levelers on the bottom of the legs. We made ours so the legs come off so it doesn't take up a lot of space when not being used.

From contributor B:
If I understand this correctly, you are looking to edge joint a board? If this is correct, then what I think I would do in your case is mount your stock to a long known straight edge. Plywood stock would be fine, and run it through the table saw keeping the straight edge against the fence.

From contributor F:
Contributor B's idea works well. I keep a straight 2"x6"x12' and a straight 2"x6"x14' to straighten wide stiff boards with on the table saw. Just put the concave edge against the straight boards’ edge and run the straight board’s other edge against the fence as you hold them both together.

After you straighten your board with the saw you can joint that edge to remove the saw marks.
It’s hard to narrow boards this way because the bow will be pushed out by your hand as you feed through the saw. Sometimes I put a few shims in between the straightening board and the hollow of the crooked board.

A more time consuming way is to clamp your crooked board along the edge of a sheet of PB or MDF and then route the edge straight with a flush trim bit. The factory edges of a full sheet are usually straight. I used this method to get my 2x straightening boards straight. I had to be done in two passes because the MDF was only 8' long.

From contributor J:
I also use the same method as Contributor F and Contributor B. I have a laminated 10' piece a ply with a stop at the beginning. I have two screws sticking out so that you can push the board into them to stabilize. At the other end I have a sliding clamp. Set your fence at the width of your sled and align the board accordingly. This will provide a straight enough edge to take to the jointer with one pass.

From contributor M:
There are lots of good methods already posted. If you do prefer to clamp a guide and trim with a router, I would suggest using an aluminum sill from a patio slider. I have one that's twelve feet long and about six inches wide. The vertical flanges for the door track and rollers create a stiff edge guide with lots of clamping surface. This comes in handy when doing a machine setup would be awkward or too time consuming for a one-time situation.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor H:
I had a similar challenge building a 10' desktop. I used a 10 foot steel stud and I checked it with a 20 foot aluminum straight ladder. It worked very well and turned out surprisingly tight.