Start from the line you marked
Cutting straight begins before the saw is picked up. The measuring and marking guide sets out the layout this page assumes: a reference face and edge, every position measured from one end, a knifed or fine line squared across from the reference, and a mark on every line saying which side is waste. The cut has one job left — to remove the waste without touching the part.
That is why this guide talks about the line rather than a measurement. Once the line is marked, the tape measure has done its work. From here, accuracy means keeping the saw on the correct side of the line and keeping it square to the reference face as it goes down through the board.
Put the kerf on the waste side
A saw does not cut a line; it removes a slot of wood called the kerf. Its width is set by the teeth, which are bent outward a little (the set) so that the plate clears the cut. Published figures show how much it varies: Lie-Nielsen gives 0.026 in for its dovetail saw, and Freud lists 0.091 in for a thin-kerf table-saw blade and 0.126 in for a full-kerf rip blade.
Whatever its width, the whole kerf belongs in the waste, with its edge just touching the line (see the plate above). If the kerf is centred on the line, half of it comes out of the part, and a series of parts cut that way each ends up short by half a kerf. When several parts come from one board, allow a full kerf between each pair — the stock cut layout does this for you.
A knifed line helps here in a way a pencil line cannot. The knife severs the surface fibres along the line, so the saw can run against a clean wall, and the fibres on the part side are already cut before the teeth arrive.
Workshop tip— Leave the line
When a cut must be exact, saw so that the line is still visible on the part after the cut, then plane or pare to it. Removing a whisker is easy; putting wood back is not.
Starting a hand cut
Most wandering cuts are decided in the first few strokes. A saw follows the kerf it has already made, so a kerf started straight tends to stay straight, and one started off the line tends to stay off it. Take the time at the start.
Starting and tracking a hand cut
Hold the board firmly
Clamp it, or hold it in a vice or on a bench hook, so that it cannot move and you do not need to steady it near the cut.
Guide the plate at the line
Rest the side of the plate against the knuckle or thumbnail of your free hand, just on the waste side of the line where it meets the far edge.
Make short, light strokes at a low angle
Let the saw’s weight do the work. A few short strokes on the far corner make a notch without the saw skating across the surface.
Lengthen the stroke and lower the saw
Once the notch holds the plate, move the guiding hand away and extend the kerf along the line on the top face.
Follow two lines at once
Watch the line on the top face and the line squared down the edge nearest you. Keeping the kerf on both keeps the cut square as well as straight.
Saw with full, steady strokes
Use most of the plate’s length and a relaxed grip. Forcing the saw makes it bend and steer.
Support the offcut near the end
Hold or support the waste for the last strokes so that it does not break off and tear fibres from the part.
Tracking the line
Stand so that the saw, your forearm and your shoulder lie in one vertical plane over the line, with your eye above the plate. From there a drift shows early. A polished plate also reflects the board: when the plate is square to the face, the reflected edge lines up with the real one.
Watch the line, not the saw. Small corrections work while the kerf is shallow; once the kerf is deep, the plate is held by the walls of its own cut and will not turn without binding.
Why a hand cut wanders
A drifting cut nearly always has one of three causes, and each needs a different correction. Deciding which one you have saves a lot of recutting.
| Symptom | Likely cause | First correction |
|---|---|---|
| Cut is off the line from the first stroke, then parallel to it | Poor start | Restart the notch on the line, guiding the plate with a knuckle; mark the start with a knife wall. |
| Cut drifts gradually and keeps drifting | Plate twisted in the kerf, or forcing the saw | Relax the grip, lighten the stroke and gently twist the handle back toward the line while the kerf is shallow. |
| Cut is straight on top but out of square down the edge | Saw leaning to one side | Watch the line on the near edge as well as the top; check your stance so the saw hangs vertically. |
| Cut curves the same way on every board | Body out of line, or a saw with uneven set | Realign shoulder, elbow and saw over the line; if the drift persists, the saw may need its set evened by resharpening. |
| Saw binds and wants to jump out of the kerf | Kerf closing, or a dull or unevenly set saw | Wedge the kerf open on long rips; a saw that binds in dry wood may need sharpening. |
For more technique faults and their fixes, see common technique faults.
Correcting a drifting cut
Catch the drift early. Turn the handle a little toward the line and saw with lighter, shorter strokes until the kerf follows it again. If the cut has wandered into the part, stop: finishing it only makes the error longer. Saw a new kerf from the other side of the line, or finish the cut on the waste side and bring the edge to the line with a plane or chisel.
Rip cuts and crosscuts
Wood is not the same in every direction. The Wood Handbook describes most of its cells as running with their long axes parallel to the trunk, which is what we see as grain. A rip cut runs along those cells; a crosscut runs across them. The two are different jobs.
- Rip cuts tend to follow the grain. Where the grain runs off the edge of the board, a rip can be led away from the line, so watch it closely and start again from the far end if needed. Rip teeth are shaped to chisel along the fibres.
- Crosscuts tear the fibres at the surface unless they are severed first, most of all on the exit face. A knifed line, and a crosscut saw whose teeth score the fibres like knives, keep the edge clean.
Tooth shape and count decide how well a saw does each job. The handsaw guide explains rip and crosscut teeth, and the backsaw guide matches the smaller joinery saws to the joints they cut.
Machine cuts follow a reference
A power saw does not see the line. It follows whatever it is guided by, so a straight machine cut is made twice: once when you set up the reference, and once when the saw follows it. The line on the board becomes a check that the reference is in the right place.
What each machine follows
- Table saw
- The blade stays put and the stock moves. For a rip, the stock is held against the rip fence, so the fence must be parallel to the blade and set to the width of the part. Crosscuts are guided by a mitre gauge or a sled instead; follow the saw’s manual on how each is used.
- Track saw
- The saw rides a guide rail. Festool describes the rail’s splinter guard as aligning the rail to the cut line and suggests replacing it when changing blades or saws, so that its edge matches the kerf.
- Circular saw and straightedge
- The saw’s base runs against a clamped straightedge. The straightedge sits back from the line by the base offset — the distance from the edge of the base to the blade — which is measured once on your own saw.
Before any machine cut, check the reference itself: a fence that is not parallel to the blade, or a straightedge that is not straight, copies its error into every cut. The setup checks cover the common ones.
Safety— Kickback
OSHA describes kickback as a saw seizing the stock and hurling it back at the operator, and notes that ripping is more prone to it than crosscutting. Use the spreader or riving knife and the guards your saw is designed with, stand to the side of the blade’s line, and support every piece of a cut — including the offcut — so the kerf cannot close on the blade. The manufacturer’s manual for your saw sets out its safeguards and procedures, and comes before any general guidance.
Which method keeps a cut straight
No one method is best for every cut. The table sets each common cut against the reference it depends on; the right choice depends as much on the size of the stock and what you have as on the cut itself.
| Type of cut | Stock | Reference | Tool approach |
|---|---|---|---|
| Crosscut to length | Boards narrow enough to saw at the bench | Knifed line squared from the reference edge | Crosscut hand saw or backsaw, often on a bench hook |
| Rip along a board | Solid boards by hand | Line gauged or struck from the reference edge | Rip saw, with the board held securely; watch for grain leading the cut |
| Rip along a board | Solid boards by machine | Rip fence set parallel to the blade | Table saw with its spreader or riving knife and guards |
| Crosscut or rip | Sheet goods and wide panels | Guide rail or clamped straightedge | Track saw, or circular saw against a straightedge set back by its base offset |
| Joint cheeks and shoulders | Parts already dimensioned | Knife lines from the reference face and edge | Backsaw, sawing to the waste side of the line |
Whichever method you use, a cut left slightly proud of the line can be brought to it with a plane or chisel.
Check the result
Check the cut against the same references you marked from. Hold a square against the reference face and the reference edge in turn: light under the blade shows a cut that is out of square. A straightedge laid along a long cut shows whether it is straight. If a series of parts must match, check them against each other as well as against the rule.
Check your square too. A square that is not square will pass a bad cut; the flip test in the setup checks finds its error in a minute.
Before you cut
Before the cut
- The line is squared from the reference face or edge.
- The waste side of every line is marked.
- The kerf will fall wholly on the waste side.
- The board is clamped or held and cannot move.
- The offcut is supported so it will not break away.
- For a machine cut, the fence, rail or straightedge is set and checked.
- Guards, spreader or riving knife are fitted as the manual requires.
- You can stand in line with a hand saw — or to the side of a machine blade.
Sources
Kerf widths, the guide-rail behaviour and the safety statements come from the sources below. The hand-sawing method is established bench practice, explained here in BenchRoot’s own words. For any machine, its manufacturer’s manual comes first.
- 1.
Alex C. Wiedenhoeft and Thomas L. Eberhardt. Chapter 3: Structure and Function of Wood. USDA Forest Service, Forest Products Laboratory — Wood Handbook, FPL-GTR-282, 2021.
Used for: The long axes of most wood cells run parallel to the trunk, which is why cutting along the grain and across it are different jobs.
- 2.
Dovetail Saw (1-SAW-DS) specifications. Lie-Nielsen Toolworks.
Used for: A published hand-saw kerf: 0.026 in on a 0.020 in plate.
- 3.
Freud Premier Fusion P410T and LM72M010 blade specifications. Freud, as listed by Rockler and Timberline Tools.
Used for: Published table-saw kerfs: 0.091 in (thin kerf, P410T) and 0.126 in (full kerf, LM72M010).
- 4.
Splinter guard FS-SP 1400/T. Festool USA.
Used for: How a guide rail's splinter guard aligns the rail to the cut line, and why it is replaced when blades or saws change.
- 5.
eTool: Woodworking — Machine Hazards — Kickbacks. Occupational Safety and Health Administration (OSHA).
Used for: What kickback is, why ripping is more prone to it than crosscutting, and the safeguards used against it.
- 6.
eTool: Woodworking — Handheld Circular Saws. Occupational Safety and Health Administration (OSHA).
Used for: Supporting every piece of the cut, and keeping hands clear of the cutting line, with a handheld circular saw.
About this guide
Written by BenchRoot Editorial. How BenchRoot sources, checks and corrects its pages is set out in the Editorial Policy. If something here is wrong or unclear, the contact page explains how to tell us.