How to Replace Jointer Knives

What You'll Need
Machinist dial gauge
Open end wrench, or hex key
Safety goggles
New jointer blade

Jointer knives, when they become nicked, damaged or warped can create unwanted lines in wood that are planed in a jointer. In addition, dull jointer knives can create rougher surfaces on your planed wood, as well as making your jointer work harder and use more electrical power. When this happens, you don't need to replace your jointer or any of its major components. Instead, replace the damaged knives. This may not be as challenging as it may at first seem. Use the information below to better understand which tools you'll need, and the steps you'll need to replace your jointer's knives.

Step 1 – Purchase Your New Blade

Take your jointer information, such as model number and size, with you to a hardware store or home improvement store that sells jointer blades. Be sure you are buying theblade size that will fit your jointer. If possible, take your old knife with you when you buy the new one.

Step 2 - Work Safely

First things first, don't take any chances. Avoid any possibility of injury by removing electrical power from your jointer before you work on it. Remove the electrical cord from its power source; then, turn on the jointer's switch to be sure the power is removed.

Step 3 – Remove the Defective Knife

Locate the screws or bolts that hold your jointer knife in place. They may be hex screws or bolts and nuts you can easily loosen with the right tool. Once you've identified these set screws or nuts, loosen them and remove the old, defective knives.

Step 4 – Attach Your New Knives

Fit your new knife into the jointer's cutter head and turn the screws or nuts tight enough to hold the knife in place. Keep it loose enough to allow you to make needed blade adjustments. Onto the out-feed bed, adjust the edge of the knife until it is in position over the cutter head. After you have positioned the dial gauge on the out-feed table, you should adjust it until it indicates zero.

Step 5 – Position the Knife

You'll need to position the knife so it is at the top position and centered. When the blade is at its highest point during its rotation, it is in the right position if it barely touches the straight edge bottom. You'll know when to tighten the blade when you see that it is touching the straightedge. Then, tighten the screws or nuts on the blade and check its position again with the gauge.

Step 6 – Test the New Knife

When you've adjusted the blade, checked it with your gauge, and tightened it; plug the jointer into the electrical socket, turn it on, put your safety goggles on, and run a piece of wood through the jointer. Finally, check the test wood piece to be sure it has been planed evenly.