 he
jointer
is a simple tool to use and essential for truing wood
surfaces. But there are two considerations of which you must be
aware. First, the jointer must be aligned and adjusted
perfectly for good results. Second,
it is one of the most dangerous tools in your shop; watch where
you place your hands.
CHECK THE
SETUP
Whenever you change or sharpen the jointer knives, check their
height relative to the
outfeed table.
At the top of their rotation, they should be almost dead even
with the table surface, maybe just 0.001 to 0.003 inch above it.
If they’re too high or too low, you can’t make a straight cut.
Too high, and the jointer will make a slightly concave cut; too
low and the cut will be convex. |
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Whenever you
move the fence, check its angle to the tables with a square or
protractor. I also suggest doing this whenever you set up to
prepare lumber for a project or do a lot of jointing tasks
even if you haven't moved the fence. It's impossible to
underestimate the amount of grief this simple precaution can
save.
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Whenever possible,
don’t just check the tool setup. Make test cuts and check the
results. Only then can you tell if the tool is adjusted
properly. |
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CHECKING THAT THE JOINTER
MAKES STRAIGHT CUTS
1
To
check that your jointer is cutting a straight edge, joint the first 1 or
2 inches of a test board to create a snipe in the edge. Shade the snipe
with a pencil.* |
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2
Turn the board around
and joint the entire edge. (You should cut the snipe last.) Check the
snipe — the knives should have shaved off most of the pencil marks, but
they should still be barely visible. If the marks are untouched, the
knives are too low in relation to the outfeed table. If they have been
removed completely, the knives are too high.* |
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CHECK THE STOCK
Because dirt is abrasive,
clean dirty wood with a stiff brush before you joint it. This will help
keep the knives sharp. Don’t joint painted wood or plywood — these, too,
contain abrasives that dull the knives. And avoid used lumber at all
costs: It may contain embedded nails or broken screws that will nick the
knives.
Also inspect the lumber to find
its grain direction and any warps, twists, or bows. Grain rarely
runs straight through a board, parallel to its surfaces. There
is usually a slight angle between the grain direction and the
face or edge. This is called the grain slope. You want
the knives to shave the wood down the grain slope, or "downhill"
as you joint. If the knives cut "uphill," they will dig into the
grain, lift it, and tear it or gouge it.
If the
board is slightly distorted, you'll want to feed it with the
concave surfaces against the tables or the fence. This way, it
will be as stable as possible while you work. If you feed it
with the convex surfaces against the jointer, the wood will tend
to rock. |
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GOOD
TECHNIQUE
As you work:
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Wax and buff
the tables and fence to help the wood feed easily. |
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Adjust the height of the
infeed table
to control the depth of cut. Make deep cuts (greater than 1⁄16 inch)
only when you must quickly remove stock. Use shallow cuts (less than
1⁄32 inch) to finish up — these leave a smoother surface. |
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Stand beside the jointer, opposite the
fence, so if
the wood kicks back, you’ll be out of the way. |
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Keep the wood firmly against the jointer fence and the tables. Start
with it pressed flat on the infeed table, then shift the pressure to
the outfeed table as you feed the wood. |
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Feed the wood slowly. This creates the smoothest possible cut. |
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Cut with the grain (or "downhill") so the wood doesn’t chip or tear out. |
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Manipulate the wood with push shoes and push
blocks to keep your hands away from the
cutterhead. |
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If the board is cupped or bowed, joint the concave surface first. |
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JOINTING WITH THE GRAIN
If
the wood chips and tears as you cut it, you are cutting against the
grain. (This is sometimes called “cutting uphill.”) Turn the wood around
and feed it in the opposite direction to cut with the grain
(“downhill”).* |
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CHECKING THAT THE JOINTER
MAKES SQUARE CUTS
Make a test
cut to determine that the jointer is cutting one surface square to
another. Don’t presume that just because the fence is square to the
tables, you’ll get a square cut. If the knives are cocked slightly, the
jointer will still cut at an angle.* |
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REDUCING MILL MARKS
Because the
jointer knives travel in an arc, each cut creates a scallop. The ridges
between the overlapping scallops are known as mill marks. These can ruin
the appearance of your project. To keep mill marks to a minimum, feed
the work slowly and use a shallow depth of cut.* |
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JOINTING SMALL PARTS
When
jointing small parts (less than 12 inches long), fasten them to the
bottom of a push shoe with double-faced carpet tape. This will help you
handle them safely.
WARNING! Never
joint anything shorter than three times the distance between the infeed
and outfeed tables, or 6 inches minimum.* |
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JOINTING AT AN ANGLE
When jointing a bevel or a chamfer, tilt the fence toward the
table. This captures the work and makes it easier to maintain an
accurate angle. If you tilt the fence away from the table, the
work tends to slide.* |
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JOINTING END GRAIN
To joint end
grain, clamp the work to a large scrap to help support it. The scrap
also backs up the stock, keeping the knives from chipping and tearing
the trailing edge.* |
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When feeding the
work, never place your hands directly over the cutterhead. If the wood
kicks back severely, your hand could drop straight into the cutterhead.
To make matters worse, the rotation of the knives will draw you hands and fingers in like a meat grinder. |
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