What's the best way to align jointer knives for sharpening?
I have a benchtop jointer with aluminum beds, and the time has come to resharpen its knives. Since most knife-setting jigs use magnets to hold the knives in alignment with cast-iron beds, how can I align the knives to aluminum jointer beds?
—Al Agnew, Salem Illinois
Al, you can still use magnets to set knives in aluminum-bed jointers. This simple and inexpensive method takes advantage of the sensitive nerves in your fingertips.
First, cut two 16" lengths of 3⁄4 ×3⁄4 " aluminum angle 1⁄8 " thick, available at hardware stores. You'll also need four 1⁄2 "-diameter rare-earth magnets.
With the jointer unplugged, gain accessibility by removing the fence and cutterhead guard. Carefully rotate the cutterhead by hand to remove the four screws that hold each knife and its gib [above]. After sharpening the knives, replace all parts and tighten the holding screws so the knives are snug but will move with light finger pressure.
Rotate the cutterhead until a knife edge is at its peak height and then engage the machine's cutterhead lock. Position an aluminum angle and two magnets at both ends of the knife. Rotate both jack screws to barely lift each aluminum angle off the outfeed table. Then lower each end of the knife so it's just a hair lower than the aluminum angle when you gently push down on the knife with your finger [below]. You should be able to feel the short distance the knife moves when you let off the downward pressure, allowing the knife to be drawn back up to the magnet. Slowly rotate each jack screw upward as you repeatedly apply and release finger pressure, alternately at both ends of the knife, until the knife no longer goes down when you apply pressure. At that point, the knife edge should be exactly level with the outfeed table. Release the cutterhead lock and tighten the gib screws. Repeat for the other knife.
Replace the fence, unclamp the guard, and test your adjustments by jointing a board edge. You may need to repeat the adjustment process, but with a little practice you'll soon master this surefire method.