How to Measure, Mark and Cut Wood Accurately, Including Plywood

“Measure twice, cut once” is the oldest rule in woodworking, and in every craft where parts are cut and assembled. Small errors in measuring and marking add up: a part that is a fraction too short, or a corner that is slightly out of square, shows up as a gap or a wobble when the piece is assembled, and sometimes the only fix is to cut the part again.

This post covers the tools for measuring and marking and how to use them, how to cut accurately by hand, and how to break down and cut plywood cleanly. For a business, accurate measuring and cutting means less wasted wood and fewer remakes.

Measuring Tools

Tape Measure

A retractable steel tape is the most used measuring tool in the shop. A 16- or 25-foot tape covers most work, from small parts to full sheets. The stiff blade stays straight when extended, and the hook on the end lets one person measure long boards. The hook slides slightly on purpose, so measurements are the same whether you hook the end or push it against a surface.

For the most accurate work, use the same tape throughout a project, since two tapes can differ slightly.

Rules

Steel rules are quicker and more accurate than a tape for short measurements and for setting tools. Sizes from 6 inches to 24 inches are common, and an inexpensive set covers most needs. Choose hardened steel; brass and aluminum rules are softer and dent or bend more easily. A folding rule gives the stiffness of a rule over longer lengths.

Some marking rules have small slots along the scale, so you can place a pencil or knife point exactly on a mark. Search for “slotted marking rule” if you want one.

Squares

Squares measure and mark angles:

• Try square: a fixed 90-degree square for marking and checking right angles. Simple and reliable.
• Combination square: a rule with a sliding head that marks 90 and 45 degrees, measures depths and sets blade heights. The most versatile square in the shop.
• Miter square: a fixed 45-degree square for miters.
• Sliding bevel: an adjustable blade that copies or sets any angle, using a protractor to set it.
• Framing square: a large L-shaped square for checking cabinets and large assemblies.

Choose squares made of steel or a solid composite rather than wood, since wood moves with humidity. A square can be out of true, even when new. To check one, draw a line along the blade with the stock against a straight edge, then flip the square over and draw again from the same point. If the two lines are not exactly on top of each other, the square is not true.

Marking

A pencil line has width, and if you cut on the wrong side of a thick line, the part can come out noticeably off size. For general work, use a sharp pencil or a fine pen and always cut on the same side of the line.

For precise work, use a knife instead:

• Marking knife: scores a fine line in the wood fibers. The line is more accurate than a pencil line, and it gives a saw or chisel an exact place to start. Use gentle pressure; a deep score is hard to remove if the line ends up on a show face.
• Marking gauge: a pin, knife or wheel set at a fixed distance on a sliding fence. Run the fence along the edge of a board to mark a line parallel to it, for joints, rabbets and thicknesses. A wheel gauge cuts cleanly across and along the grain.

Mark which side of each line is waste, with a cross or scribble, so you never cut on the wrong side.

Measuring Habits That Prevent Mistakes

• Measure, mark, then check the mark before cutting.
• Where possible, mark a part from the piece it must fit rather than from a number. For example, build a cabinet, then measure the opening for the drawers.
• Use a story stick, a strip marked with all the key dimensions, for products you make repeatedly.
• Use stops on saws and fences for repeated parts, so you measure once for the whole batch.

For stop blocks, story sticks and other jigs for repeated parts, see woodworking jigs and batch production.

Cutting by Hand

The right saw makes cutting easier: a rip saw for cutting along the grain, a crosscut saw across it, a backsaw for joints and a coping saw for curves. See woodworking hand tool basics for the types of saw and how to choose one. Whichever saw you use, the technique is much the same:

• Grip. Hold the handle with your index finger pointing along the side of the blade. This steadies the saw and helps you steer. Frame saws and coping saws are often held at the frame with the free hand; Japanese pull saws are stiff enough that you may not need the extended finger.
• Start gently. Draw the saw back a few times to make a small notch, guiding the blade with the thumb of your other hand kept well above the teeth. Start full strokes only once the teeth are in the wood.
• Secure the wood. Clamp the work firmly. Wood that moves spoils the cut and can cause an injury.
• Stand behind the saw. Line up your shoulder behind the blade and use long, even, rhythmic strokes. This spreads the effort and reduces fatigue.
• Cut on the waste side. Keep the blade on the waste side of the line, so the finished part keeps its full size.
• Support both sides. Support the offcut so it does not sag and tear away before the cut is finished.

Cutting Plywood

Plywood sheets are large, heavy and expensive, and their thin face veneers splinter easily. Cutting them cleanly takes planning.

Moving Full Sheets

A full 4 by 8 foot sheet is heavy and awkward. Use a panel cart or rolling dolly to move sheets around the shop, get help when you can, and lift with your legs. Many home centers and lumberyards will make rough cuts for you, which helps if a full sheet will not fit in your vehicle or through your shop door.

Breaking Down Sheets With a Circular Saw or Track Saw

Cutting a full sheet on a table saw is difficult and risky without help and good support. It is easier to cut sheets into smaller pieces first with a circular saw or track saw, then make final cuts on the table saw.

• Lay a sheet of rigid foam insulation, about 1 1/2 to 2 inches thick, on the floor, and lay the plywood on it. The foam supports both sides of the cut, so nothing drops or pinches the blade, and it lasts for many sheets.
• Set the blade to cut just through the plywood and slightly into the foam.
• Use a straightedge guide or a track saw for straight, clean cuts.
• Put the good face down. A circular saw blade cuts upwards, so splintering happens on the top face.

Cutting Plywood on a Table Saw

• Support the sheet. Set up outfeed support, such as a roller stand or outfeed table, slightly lower than the saw table and in line with the blade. If it is not straight, it can push the sheet off line.
• Stand to the side. With a large sheet, stand to the left of the blade, not directly behind it, so you can push forward and press the sheet against the fence at the same time. Watch the edge at the fence to catch any drift.
• Good face up. A table saw blade cuts downwards, so splintering happens on the bottom face. This is the opposite of a circular saw.

Preventing Tear-Out

• Use a sharp, carbide-tipped blade with many teeth, or a blade made for plywood. They take small bites and leave a clean edge.
• Score the cut line with a knife, or apply masking tape along it, before cutting.
• Use a zero-clearance throat plate on the table saw, or a splinter guard on a track saw.

Cut Large, Then Trim

Trying to cut a large sheet straight to final size often goes wrong. Cut the pieces slightly oversize first, then trim to exact size once they are small enough to handle. It wastes a little material but gives more accurate parts and avoids remakes.

Plan for Grain and Yield

Hardwood plywood faces show grain, and the pattern changes across a sheet. If cabinet doors or panels are cut from different parts of a sheet without planning, they may not match when assembled. Lay out matching parts next to each other on the sheet so their grain flows, even if that uses a little more material.

For everything else, plan cuts to get the most parts from each sheet. Draw the sheet to scale and fit the parts on it, or use cut-list software, which arranges parts to reduce waste. Allow for the width of each saw cut.

For plywood types and grades, see types of wood for woodworking.

Safety

When cutting with a circular saw, Canada’s Centre for Occupational Health and Safety advises setting the blade so the lowest tooth extends no more than about 1/8 inch below the wood, securing the work so it cannot move, standing to the side of the saw, and using two hands. Use push sticks and the riving knife on a table saw, and wear eye and hearing protection. See woodworking safety rules and circular saws, track saws and jigsaws.

Practical Tips

• Use good-quality squares and check them regularly.
• Use a knife line where accuracy matters, and always mark the waste side.
• Measure from the parts themselves where you can.
• Break down sheets with a circular saw or track saw before final cuts.
• Cut slightly oversize, then trim.
• Plan sheet layouts to save material and match grain.

Sources

• Canadian Centre for Occupational Health and Safety, n.d., Powered Hand Tools: Saws, Circular, CCOHS