Jointer Knife Adjustment Jig
Adjusting jointer knives is a shop task often misunderstood and too often neglected. This doesn't have to be the case. Many methods and jigs exist (some very involved and others quite expensive) to help you set jointer knives.
Like most woodworkers, you probably don't want to spend a lot of time or money on tool maintenance. If your jointer's cutterhead has jackscrews here's how to get the job done in no time with an inexpensive dial indicator (less than $20) and a shop-made holder. Begin by making the holder (at right), and then follow these steps.
Step 1: With the tool unplugged and the knives removed, clean all dust and debris from them, the gibs, and the cutterhead slots. Lightly coat the parts with a light machine oil to help make adjustments easier and to keep parts from freezing together. If the knives need sharpening, take them to a professional. Note: during tool start-up, any excess oil will quickly fly off the cutterhead and not contaminate your work.
Step 2: Place the knives in the cutterhead, making sure they sit below the outfeed table height. Snug the gib bolts to hold the knives in place. Do not tighten yet.
Step 3: With the dial indicator mounted in the holder (as shown in the top photo) and positioned over the outfeed table, turn the dial's outer ring until it reads zero.
Step 4: Position the dial indicator foot over the knife, centering it on the cutting edge. The dial should read less than zero. Note: A flat foot on the dial indicator makes locating the edge center easier, but an indicator's bullet tip also works.
Step 5: Using an Allen wrench and the jackscrews in the cutterhead, raise the knife until the dial reads zero along the entire length. Tweak each end of the knife to reach the desired height.
Step 6: Gradually tighten the gib bolts in this order: Start with the far bolt, as shown, then the near bolt, then the far inside bolt, and finally, the near inside bolt. This so the knife won't creep upward and need readjusting. Recheck the knife height, and repeat Steps 5 and 6 on the remaining knives. Check all bolts and guards before turning on the jointer.
If you like this project, please check out more than 1,000 shop-proven paper and downloadable woodworking project plans in the WOOD Store.