Woodworkers use planers to smooth rough wood and to reduce the thickness of a board. A planer does this by removing small shavings of wood with a rotating cutter head that holds two or three knives, depending on the model. The DeWalt planer has three knives in its cutter head, but unlike those in other models, the DeWalt knives have a dual edge, so when one edge wears out, you just need to remove the blades and turn them over to continue working.
Disconnect the planer's power cord, then use the T-wrench that comes with the planer to remove the four screws that secure the top of the planer. Lift the top to remove it from the planer.
Remove the three wing nuts holding the dust cover over the cutter head. Rotate the dust cover up to unlock it from the fan housing, then push the cover to the left to disconnect it. Remove the dust cover from the planer to expose the cutter head.
Rotate the cutter head with a piece of scrap wood until the lock on the side of the cutter head engages. All eight screws in the cutter head clamp should now be visible. Remove the screws using the T-wrench, then turn the T-wrench upside down and use the magnet in the head of the T-wrench to grab the clamp. Remove the clamp to expose the knife underneath. Use the magnet to remove the knife.
Turn the blade around so the sharp edge is facing up; return the blade to the cutter head. Put the knife clamp back over the blade. Align the beveled edge on the clamp with the cutting edge on the blade. Put the screws back in the cutter head and tighten.
Press down on the cutter head lock to free the cutter head. Use some scrap wood to turn the cutter head for access to the remaining two knives. Follow the instructions in Steps 3 and 4 to remove and replace those knives.
Insert the round end of the dust cover into the fan housing and rotate the cover down until it locks into place. Put the three wing nuts back on the dust cover. Replace the planer top and screw it down.