By Jeff Jacobson
Discover new life for your warped, cupped and twisted
stock by putting three essential power tools to work in
your shop. Save money by starting with rough-cut lumber
— and save lumber with these surfacing secrets.
A special excerpt from the May/June 2006 Woodworker’s Journal
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37
Copyright 2007 Rockler Press, Inc.
SECRETS TO SURFACING STOCK
By Jeff Jacobson
The relationship between your jointer, planer and table saw
is critical to properly preparing stock. Whether you are cleaning up
rough-sawn lumber or correcting cupping, warping or twisting — you
need all three tools (and a set of winding sticks) to succeed.
Here’s the deal ... planers do not flatten wood, they
surface wood. Put a rough-sawn twisted or warped
board through a planer and you get a smooth,
twisted or warped board. So, how do you deal with
those deformed pieces of valuable lumber? You
could use a hand plane to flatten the wood, or you
can use the combination of a jointer, planer and
a saw (in this article a table saw). With these three
tools working in concert, you will make short shrift
of snaky stock. To do so, you’ll need to follow the
basic steps shown here.
1
A word about jointers. As indicated, a jointer is
the key to dealing with distorted lumber. By face
jointing, you can deal with cups and twists. And to
that end, you can’t truly face joint anything wider
than the width of your jointer’s cutterhead. A 6"
jointer will handle up to a 6" wide board; 8" jointers,
an 8" wide board, etc. Jointers are also one of the
more dangerous tools in a shop. If you get your
finger tangled up in a jointer head, the motion of the
cutter will pull your finger into the head with great
power. Always use guards and safety gear when
using a jointer. The space available here is
insufficient to adequately cover jointer safety in
detail. Proper use of your tools is an individual
responsibility.
2
STEP 2. Face joint the two pieces
of wood. Joint the same face
of each separate piece.
Continue this operation
until there is a flat surface
over most of each board.
Remove the same
amount of stock by
performing the same
number of cuts
on each
piece.
STEP 1. Use a table saw to rip the
cupped board down the middle of
its cathedral grain. If it won’t be
obvious, mark the pieces so they
can be glued back
together at
the end of
this process.
39
A special excerpt from the May/June 2006 Woodworker’s Journal
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Copyright 2007 Rockler Press, Inc.
The Consequences of Wood Movement
Warping
Cupping
As freshly cut (green) wood dries, the cells that make up the wood fibers actually shrink.The problem is that the fibers shrink
almost twice as much in one direction (tangential) as they do in the opposite direction (radial). Depending on how the grain
or wood fibers run through the length of a board, this shrinkage differential will cause the wood to distort. Once a board
is “dry,” that shrinkage can be addressed and corrected. Cupping and warping are two of the easier distortions to correct.
FIVE STEPS TO CORRECTING CUPPING
Often, wide boards with beautiful cathedral grain are
significantly cupped. Visually, the board would be
a perfect selection for a tabletop or desk, but it’s too
cupped to use. So, how do you flatten the board but
retain its visual integrity? Follow the five steps
starting at left. (For a narrow board 8" or slimmer —
depending on how wide your jointer is — you can
start on step 2.) And remember, once a board is
properly dry its tendency to distort will abate.
4
3
STEP 3. Move to your planer
and begin surfacing the
stock. Continue until you
have a smooth flat surface
on both faces of each board.
Because you face jointed the
boards, their faces are now
parallel to each other.
STEP 4. Square the edges of the saw cut to exactly 90˚. You have
now re-formed the two sections of your wide cupped board into two
perfectly flat boards with prepared glue-joint edges.
5
STEP 5. Glue the pieces back together, taking time to ensure that
the grain matches at the glue joint, the glue-up is flat and the
edges are properly aligned. You now have a flat, stable, wide panel.
A special excerpt from the May/June 2006 Woodworker’s Journal
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Copyright 2007 Rockler Press, Inc.
1
Twisting
Twisting is the mother of all board distortions. Fixing
a twist is tricky because material needs to be removed
in an asymmetrical fashion. Also, more stock usually needs
to be jointed away in order to harvest usable material.
STEP 1. Evaluate segments of the warped board to access whether
you can get your desired part out of the piece. A template of the
part (on the saw table) is very useful during this process.
FIXING WARPS AND TWISTS
As with the example of cupping, when you decide to
fix a specific problem of wood distortion, it should
be with a goal in mind. In this example, the goal is
to har vest a specific part from a board that
is warped. It only makes sense that if you have
to straighten 18 lineal inches, the task will be easier
and waste less material than removing material
to straighten 36 lineal inches. For that reason, the
evaluation phase of this process is best done with
specific parts in mind. The limitation to producing
useable parts from a warped board is the thickness
of the wood required to make a specific part. The
full dimension of the part must exist within the
volume of the wood you are machining. If, by reason
of the wood’s curvature over its length, you need to
remove so much material that the board’s thickness
is less than that of the part, you need to find another
piece of wood or move to a different segment of the
warped board you are looking at. The curvature of
a warp will not be uniform down its length, so you
might be able to produce a specific part from one
section of the board, but not another.
For all of these reasons, the first step in dealing with
a warped board is evaluation. When you have
determined which segment of the overall board can
produce the part you want, cut that section
out. As the next step is face jointing, do not
cut out a piece that is too small to safely face
joint ... 16" is a minimum safe length.
4
STEP 4. Plane the
stock flat with
parallel faces. The
length of the piece is
important here, too.
3
STEP 3. Don’t assume that your stock is out of twist just because
you face jointed it. Check your piece with a pair of winding sticks.
A minute of patience is worth an hour of power.
A special excerpt from the May/June 2006 Woodworker’s Journal
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Copyright 2007 Rockler Press, Inc.
2
TWIST
AND
SHOUT
In the front view
photo at left, the
colored lines are
used to indicate
differing planes
or levels on the face
of this twisted piece
of persimmon wood.
The white lines
indicate the level
farthest from the
mean. Yellow is next,
with magenta
representing the
lowest level of the
board. The goal
of face jointing this
board would be to
remove the white
outlined area first.
Next, move to the
yellow area. When
you get to the
magenta plane,
the board’s face
will be essentially
level or flat.
STEP 2. After you cut out the piece of stock appropriate for your
part, face joint the piece. For safety’s sake, the piece should be
at least 16" long. It is better to waste a bit of wood than get hurt.
After that, the process is very similar to that
described in “Five Steps to Correcting Cupping.”
The only caveat is that you’ll need to check the
board for twist after you face joint. Do this with
a pair of shop-made winding sticks (photo 3 of this
“red” sequence). Proceed through the steps and
you will end up with a flat, parallel and square piece
of wood from a warped source.
Dealing with twisted boards is essentially the
same as the process of dealing with warped stock.
The key difference is how you address the face
jointing. See the sidebar at right.
5
Side View
Front View
Think of the surface of a twisted board in terms
STEP 5. With the stock flat and the faces parallel to each other,
joint the edges square. The piece is now ready to be formed —
from warped board to useful stock in five simple steps.
of a topographic map.The colored contour lines in
the picture above represent the “hills” and “valleys.”
The goal of face jointing in this case is to level off
the “hills.” Use your jointer to take off the high
points a bit at a time. Again, as with a twisted
board, it is always more effective to flatten smaller,
piece-specific, sections of the board.
42
A special excerpt from the May/June 2006 Woodworker’s Journal
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Copyright 2007 Rockler Press, Inc.