Instead of sending your jointer knives out to be sharpened, save money (and time) by sharpening them yourself. All you need is glass, sandpaper, and a couple of scraps of hardwood.
8_90_SharpenKnives.jpg (

Fashion a guide block, as shown in the drawing below, about 4 - 6" longer than your knives, with one edge beveled to match the grind of your knives. Joint or sand that edge smooth. (I sanded down to 320 grit and waxed the bevel).

Make a pushblock the same length as and 18 " thinner than the width of your knives. Joint one edge of the pushblock flat and attach a knife to it with cloth-backed double-faced tape.

Next, glue a sheet of 220-grit wet/dry sandpaper to a flat sheet of glass and lay your guide block on the abrasive. Keeping the knife flat against the beveled edge of the guide block, as shown, stroke the knife back and forth to sharpen it. I work my way from 220-grit up to 600-grit sandpaper for a superfine edge.

Finally, flatten the knife's back by switching the pushblock to the other side of the knife. Remove the burr by sliding the knife back and forth across the 600-grit abrasive a few times without the beveled guide block.
—Eric Sutton, McDonough, N.Y.