How to Change Jointer Knives

Unplug the power cord from the wall socket. Remove the small attaching screw from the blade guard located near the upper drive pulley. Slide the blade guard sideways out of the jointer.

Rotate the drive pulley to position one of the blades in the opening between the infeed and outfeed jointer tables. Clamp both sides of the drive belt onto the lower pulley with an adjustable clamp. This will prevent the cutter head from turning while you remove the knives. Undo the four knife locking bolts with a 1/4-inch open-ended wrench. Lift the knife together with the locking bar out of the slot in the cutter head. Repeat with the other two knives and remove the adjustable clamp from the drive pulley.

Soak the locking bars and bolts in a water-based solvent for a few minutes to loosen any built-up coating of sawdust mixed with resin and grease. Clean out the knife slots in the cutter head by digging out the caked residue with a small screwdriver, then cleaning with a 1/2-inch paintbrush and solvent. Wipe the cutter head and locking bars clean with a paper towel.

Insert the new jointer knives into the slots in the cutter head and replace the locking bars. Snug the bolts down by hand, so that the knives can move easily during final adjustment.

Place a long steel machinist's straightedge on top of the outfeed table with the flat side against the jointer fence. Adjust the infeed table until it meets the straightedge with the two surfaces at the same height. Lock the table. This should be the zero position on the height adjustment wheel. If you need to re-zero the positive stops on the infeed table, consult your owner's manual for recalibrating instructions and carry out the adjustment.

Replace the straightedge with a steel machinist's ruler. Rotate the upper cutter head pulley to locate the top-dead-center (TDC) point of one of the blades by moving it from side to side and judging the gap between the cutting edge and the ruler. Mark this point on the fence with the tip of a utility knife. Score a vertical line onto the fence with a metal scribe and the edge of the machinist's rule to mark the TDC point for future reference.

Lower the infeed table. Place the jointer blade alignment jig on the outfeed table and position the left side of the jig against the fence. Line up the front guide mark on top of the jig with the TDC line on the fence. Scribe another line on the fence to coincide with the rearmost guide mark on the jig. This will allow you to quickly position the jig during future knife changes.

Loosen the locking screws on the first knife locking bar so that the blade can move freely. Rotate the upper drive pulley until the edge of the loosened knife meets the TDC mark on the fence. The front bar on the blade alignment jig is a powerful magnet. This will snap the knife up and align the cutting edge perfectly with the upper surface of the outfeed table. Tighten each locking bolt carefully with the wrench without disturbing the blade alignment. Repeat by locking down the other two knives.

Slide the blade guard back into the jointer and replace the screw. Reset your drive belt spring tension if necessary. Plug the power cord back into the outlet.