Is it possible to use a router table as a jointer? Here's the answer, courtesy of our friends at the Woodworker's Journal.
John Brock: Yes, a very narrow jointer, good for edge joining but too narrow for face jointing. Make sure your infeed and outfeed guides are long enough and rigid enough, then you can set it up like a jointer layed on its side.
John Swanson: It is very easy to joint a board on a router table. It requires a straight bit and an offset fence. Make multiple passes, cutting on the left side of the bit until the edge is jointed.
Richard Jones: Yes. You can use an inverted table-mounted router to straighten narrow edges. Offset the outfeed table by the depth of cut set by the infeed table.
From the Woodworker's Journal eZine 2005 archives
Using a router table as a jointer is a good option if you're working in tight quarters or on a tight tool budget. The main drawback is the time it takes to get the fence set up with the correct offset. If you own a Rockler router table and fence, your in luck. Rockler offers a set of Router Table Jointing Shims that make setting up to use your router as a joiner quick and painless. It's a simple procedure - here's all that's involved:
Unplug the router and chuck-up a straight bit. - we recommend a bit with a wide diameter for the smoothest cut.
Select the shims from the set that correspond to the amount of material you want to take off with each pass. The combined thickness of the shims in one pack is .070". That's a little over 1/16", and about as much as you'd ever want to take off in one pass through a jointer.
Loosen the subfence on out-feed side, slide the shims in place and re-tighten the subfence. The shims are slotted to match the bolt pattern on the Rockler fence, so there's really no way to get this part wrong.
Place a straightedge along the out-feed side of the fence and move the fence so that it's aligned with top-dead-center of the cutting edge of the router bit (so that the out-feed side of the fence is set at a cut depth of zero, in other words). To get an accurate setting, rotate the bit by hand and watch the gap between the edge of the bit and the straightedge to make sure you are setting the fence in line with the highest point of the bit's cut radius.
Tighten the fence down, and you're ready to go. The whole process shouldn't take more than about ten minutes. If a jointer isn't in the budget, or if you'd rather not give up the shop-space, there's really no quicker or more economical alternative for putting a perfect edge on your stock.