Q & A: Setting Jointer Knives

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.