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Q & A: Setting Jointer Knives

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Q & A: Setting Jointer Knives

Q:

How can I set my jointer knives without using a jig?


A:

A wood block and a pencil will do the job on a jointer with an adjustable outfeed table. If the outfeed table on your jointer doesn’t adjust, you’re better off using a magnetic jig or dial indicator.

Make a maple block about 3/4-in. thick, 3-in. wide, and 12- in. long. Unplug the jointer. Remove the pulley guard so you can rotate the cutterhead by hand. Leave the dull knives in place.

You’ll use the block to measure the height of the knives above the cutterhead. Set the block on the outfeed table, as in the photo below. Press down lightly on the block and rotate the cutterhead. The knife should tick against the block or lift up the block and carry it a short distance.

Next, lower the outfeed table until the block moves about 1/4-in. as you manually turn the cutterhead. Using the edge of the outfeed table as a reference, mark the movement of the block from where the knife picks up the block to where it lets it down. This indicates how high the knife sticks up above the cutterhead. Now you can remove all the dull knives and have them sharpened.

The idea is to set the sharpened knives at the same height as the old ones. Put in a sharp knife. Rotate the cutterhead and raise or lower the knife until the block travels the distance marked. Check both sides and tighten down the knife, then check again. Set the other two knives the same way, and then raise the outfeed table until each knife barely ticks the block. Make sure all the knives have been tightened down, then plug the machine in and joint a 3-ft. board. Raise the outfeed table if there’s snipe at the end of the board. Lower the table if the cut trails off to nothing.



This story originally appeared in American Woodworker June 1999, issue #73.

June 1999, issue #73

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