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Rough lumber is not flat, square, or the thickness you paid for. A 4/4 board arrives at 7/8 inch or a little more, with cup, bow, and twist from drying, plus saw marks from the mill. Before any joint can be laid out, one face has to become flat and one edge square to it, and that work is mostly stock removal.
Power tools make this fast, but the hand-tool sequence is clearer about what is happening. A scrub plane takes the board down toward flat, a fore plane refines the surface and removes the scrub plane's scallops, and a jointer or smoother finishes the job. Each plane carries a different camber, and the camber is what separates them.
What follows is the order of operations, the geometry behind it, and the checks that tell you when to stop removing stock and start refining.
What Rough Lumber Asks of You
The first job is a flat reference face, not a finished surface. Put the crowned side up and plane it until a straightedge stops rocking. Working the concave side first is a common mistake: the board rocks on the bench, the plane follows the curve, and the cup gets worse instead of better.
Remove the minimum. Most mill marks clean up in 1/32 to 1/16 inch (0.8 to 1.6 mm), and a board with 1/8 inch of cup will lose about that much thickness before it sits flat. Mark the face you choose with chalk so you do not lose track once both sides look alike. Choose the face with fewer knots and less figure as the reference, because it will be the show face later.
Scrub Plane Geometry
A scrub plane is short, narrow, and heavily cambered. The classic No. 40 has a 9-1/2-inch sole, a 1-3/4-inch iron, and a camber of roughly 3 inches radius. The mouth is wide, often 1/4 inch, and many scrub planes run a single iron with no chip breaker, because a thick shaving has nothing to curl against.
That camber is the whole design. A straight iron taking a 1/16-inch cut across a 1-3/4-inch width would demand enormous force and choke the mouth. A cambered iron enters the wood at one point and exits at another, so the cut is progressive: a narrow scoop, 1/4 to 1/2 inch wide, that lifts a thick shaving without stalling the plane. The scallops left behind look alarming, and they are supposed to. The fore plane removes them.
Hone a scrub iron at 25 to 30 degrees and do not fuss over polish. It is a roughing tool. Keep the camber even on both sides of center, or the plane will steer. Setting a camber is easier with a coarse stone and a free hand than with a guide set for a square edge.
Fore Plane and Jack Plane
The fore plane is the next step up in length and down in camber. A No. 6 is 18 inches long with a 2-3/8-inch iron, usually cambered to an 8- to 12-inch radius. That gentler curve removes the scrub plane's ridges, spans enough length to straighten the board, and still takes a useful shaving of 0.005 to 0.010 inch. A No. 5 jack plane at 14 inches, cambered to about 10 inches, does nearly the same work and is the better single plane if you only own one.
Set the chip breaker 1/32 to 1/16 inch behind the edge and open the mouth to about 1/16 inch. The chip breaker still matters at this stage: a thick shaving can lift fibers ahead of the cut, and a close breaker bends the shaving before it splits. Chip breaker setup is worth getting right even on a roughing plane, because the fore plane often makes the first surface a cabinetmaker can see.
Reading Cup, Bow, and Twist
Cup is a curve across the width, bow is a curve along the length, and twist is a wind from corner to corner. They need different checks. A straightedge laid across the board finds cup; one laid along the length finds bow; a pair of winding sticks at each end finds twist.
Winding sticks are two straightedges of identical height. Place one across each end, sight over the near one at the far one, and any twist shows as the far stick leaning relative to the near one. A 1/16-inch error is obvious at 4 feet. Making and reading winding sticks takes an hour and pays for itself on the first twisted plank.
Mark the high spots with pencil before you cut, then take one pass and look at what remains. Pencil left in the middle of a cup means the plane is bridging; pencil left at the ends means it is scooping. The pattern of remaining marks tells you more than the shaving does.
Diagonal Strokes and the Grid
Roughing is done across the grain, at roughly 45 degrees to the long axis, because a cross-grain cut lifts fibers over a short distance instead of splitting along a long one. Work a set of parallel strokes from one corner to the opposite edge, then turn the board and work a second set at 45 degrees the other way. The two sets form a crosshatch, and the crossing cuts keep the surface from developing a single dominant grain direction of tearout.
Overlap each stroke by half its width. A scrub plane cuts a narrow scoop, and half-overlap turns those scoops into a continuous surface without leaving ridges between passes. Move along the board methodically rather than working randomly; a grid of strokes is easier to remember and easier to inspect.
Once the board is flat, switch to the fore plane and work along the grain in long strokes. The diagonal grid has done its job when a straightedge no longer rocks in any direction.
Knowing When to Stop
Stop roughing when three things are true: the straightedge does not rock along or across the board, the winding sticks are parallel, and the thickness is within about 1/16 inch (1.5 mm) of the final dimension. That last number is the working allowance for the jointer and smoother, which will remove 0.003 to 0.005 inch per pass and need several passes to erase the fore plane's tracks.
Continuing to scrub past flat only makes the board thinner. A scrub plane cannot improve a flat surface, and every extra pass adds a scoop that must be removed later. If the board is flat but still marked, change tools rather than taking another roughing cut. Jointing the edge comes after the face is flat, not before.
Grain Direction at the Rough Stage
Cross-grain roughing deliberately ignores grain direction, which is why it works on boards with reversing figure. The cut is short and the fibers are severed rather than split, so the surface stays intact even when the grain dives and rises.
That changes the moment you go along the grain with the fore plane. Read the edge of the board again: if the fibers rise toward one end, work from that end. A knot or a patch of curly grain will still tear, and the fix is a lighter cut, a sharper iron, or a different approach angle, not more force. Tearout in figured wood usually shows up at this stage and is better handled now than after the board is dimensioned.
Troubleshooting: Tracks, Tearout, and Rocking
Ridges between passes mean the camber is too tight or the overlap is too small. Widen the overlap to half the stroke and lighten the cut; if the ridges persist, move to the fore plane earlier than planned.
Tearout around knots comes from a dull iron or too deep a cut. Hone the iron, reduce the depth to 0.003 inch, and try the opposite direction. If the tearout is deep, stop and plane around the knot rather than through it; the smoother can blend the area later.
A board that keeps rocking after several passes usually has a hollow sole or a plane that is too short for its length. Check the sole with a straightedge, and if it is out, flattening the sole may be the real fix. Chatter, a washboard pattern across the cut, means the frog is loose or the board is unsupported at the ends. Tighten the frog and support the work before taking another pass.
A scrub iron is sharp enough to open a hand, and roughing produces more chips than dust. Keep the board against a planing stop, keep both hands on the plane, and never plane toward your body.
Frequently Asked Questions
Can I flatten a board with only a jack plane?
Yes, with patience. A jack with a moderate camber can rough and refine, but it is shorter than a fore plane and follows the board's error more closely. Check with a straightedge every few passes and take lighter cuts as the board comes flat.
How much stock should I remove before switching to a smoother?
Leave about 1/16 inch for the jointer and smoother. That is enough to remove the fore plane's tracks and still leave the final thickness under your control.
What is the difference between a scrub plane and a fore plane?
The scrub is short with a 3-inch camber and a wide mouth; it removes thick shavings fast and leaves scallops. The fore plane is longer with an 8- to 12-inch camber; it straightens the surface and removes the scallops.
Do I need a scrub plane for lumber that was already planed?
Usually not. Skip-planed or surfaced stock needs only a fore plane or jack to true it. A scrub earns its place on rough, twisted, or thick stock where you need to remove 1/8 inch or more.
Why does my board keep rocking on the bench?
Either the face is still twisted or the bench top is not flat. Check the bench first with a straightedge, then check the board with winding sticks. A rocking board cannot be planed flat until the support underneath it is stable.
See Also
- Edge Jointing by Hand: A Jointer Plane Workflow That Produces Dead-Straight Edges
- Block Plane Tuning and Five Jobs It Does Better Than Any Other Tool
- The Science Behind Hand-Plane Setups: Why a 0.002-Inch Mouth Opening Eliminates Tear-Out
- 10 Must-Have Bench Clamps for Hand-Plane & Chisel Workflows in 2026
- 5 Proven Methods for Mastering the Spokeshave: From Cabriole Legs to Custom Guitar Necks