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The jointer
is one of the oldest power tools around, yet itıs still widely
misunderstood. Its job is to create straight edges and flat faces
on the boards you use, and it does this better than any other
tool on the planet. The business portion of a jointer is its long,
flat top, more properly called the bed. This is divided in the
middle by a rotating cylinder of metal that holds a pair of blades.
Wood is pushed over the jointerıs flat top by hand, removing a
thin layer of wood from the underside of the board, making it
flatter and smoother than before. Benchtop jointers typically
take no more than a 6-inch wide swath in one pass, making them
seem silly next to the more popular wood-dressing tool, the 12-inch
thickness planer. Donıt be fooled. To appreciate the subtleties
of what a jointer does -- and what a thickness planer cannot do
-- you have to understand the process of smoothing and straightening
wood.
Step#1:
Getting a Flat Face
Every board
deviates from a flat shape in some way. You could be faced with
a trough-shaped, crowned or twisted board. The first step in truing
any board is to run one, wide face (not an edge) over the jointerıs
blades. Several passes will remove high spots, imparting a flat
surface where a warped one existed before. If you had tried this
with a thickness planer youıd get a smooth surface, but not a
flat one. Here's why:
Inside every
thickness planer are two high-pressure drive rollers that draw
wood through the machine. As these rollers operate, they push
down on the wood, temporarily removing any warp or twist in the
board. The wood is planed in this flat state, but as the roller
pressure is released, the imperfect board springs back to its
original shape from the same internal forces that caused it to
warp in the first place. The jointer doesnıt have this effect
because wood is guided over it by hand, under virtually no downward
pressure at all. As long as you prevent the board from wobbling
during each pass, youıre assured a true, flat face. This is the
starting point for all good woodwork.
Step#2:
Preparing a True Edge
The top of
any jointer has a part called the fence. Itıs the adjustable guide
strip that sits perpendicular to the bed. Although the fence didnıt
enter into things during step #1, it does now. The purpose of
the fence is to support wood, on its edge, at a certain angle
relative to the jointerıs bed. The angle of choice is almost always
90 degrees, though fences can be adjusted anywhere from 45 to
90 degrees. Your job now is to slide your wood along the bed of
the jointer with the face you milled earlier pressed firmly against
the fence. This imparts two qualities onto the edge being milled:
straightness, and a 90-degree corner relative to the face you
milled initially.
Step#3:
Milling The Other Face
This is where
the thickness planer comes into play, if youıve got one. Since
the jointer has created one flat face for you in step#1, the boardıs
other face can now be milled in the thickness planer without distortion.
With the true face downwards on the thickness planerıs bed, the
high-pressure drive rollers cannot distort the wood as it passes
through the machine. If you donıt have a thickness planer you
could mill this second face on the jointer too, but youıll have
to be careful not to create a board thatıs tapered in thickness.
Flipping the board end-for-end after each jointer pass will help
avoid this.
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