Cutting a slot in plywood for a band saw blade passage

A reliable method for cutting a slot in plywood for a band saw blade passage depends on what the opening must do. It may be the kerf left when plywood is being cut, or a clearance opening that lets a bandsaw blade move past an installed panel. Those are different jobs: the first follows the tooth path, while the second must accommodate tracking, wear and any guide hardware. A carefully measured opening keeps the blade from rubbing and helps the cut stay straight.

Australian workshops often start with plywood bought through Bunnings, Mitre 10 or a local timber merchant. Common sheet sizes are 1200 by 2400 mm, with 17 and 18 mm thicknesses, although labels and actual sheets can differ. Many Australian woodworkers say “bandsaw” and refer to their workshop space as the “shed”. Sloan’s Woodshop in Tennessee is a useful specialist reference, but its stated shipping area is the United States, so Australian shoppers should check freight, tax and exchange-rate implications separately.

Identify the opening your project needs

The first decision is whether the plywood is the material being cut or a fixed part of a jig, guard or machine bed. In the first case, the bandsaw creates a kerf as wide as its toothed path. In the second, the blade must pass without touching the panel edges, so the opening needs to be slightly wider than the blade’s swept profile. A third arrangement uses a narrow access slot from an edge to an internal cut, allowing a bandsaw to reach a shape it cannot otherwise enter.

Watch the machine before marking anything. With the power isolated, note the position of the upper guide and any component that must cross the plywood. Look for places where the blade moves from side to side or where worn teeth project beyond the nominal blade width. Do not confuse a local passage with the saw’s factory throat opening; enlarging a machine’s guarded slot can affect blade support and should only follow the manufacturer’s instructions.

Blade selection also affects the opening. Sloan’s Woodshop lists band saw blades in several widths and tooth configurations, while scroll saw blades are better suited to narrow, controlled openings. Record the actual dimensions of the blade fitted to your saw rather than relying on a packet label, because tooth set, wear and blade type can change the space needed.

Measure the blade and mark the plywood

Measure the saw rather than the packet. Check the blade width across the teeth, its thickness, the amount of tooth set and any visible wear. Make a full-size gauge from thin cardboard or an offcut of plywood. Position it around the stationary blade and trace the complete area that the blade can sweep, including any guide hardware that passes through the proposed opening.

For a static passage, use a scrap test piece to establish the running clearance. An allowance of about 1 mm per side is a reasonable trial for a small opening, but the saw manual and the machine’s geometry take priority. The finished slot should provide positive clearance without so much movement that the panel becomes unstable. For an access slot, make the opening wide enough for the toothed path and long enough to reach the internal cut without the blade contacting an edge.

Mark both sides of the plywood and join the marks with a straightedge. Masking tape over the line reduces splintering and makes the pencil marks easier to see on dark or textured faces. Add small relief cuts at sharp inside corners so waste can fall away without forcing the blade sideways. Clamp the sheet securely to the bench, support narrow sections with a solid backing block and keep the marked line clear of clamps.

If the slot belongs to a shaped plywood assembly, such as a laminated deck or composite panel, the surfboard plan guides show how layered pieces relate spatially. Use that kind of reference for the overall component, while taking every clearance measurement from your own saw and sheet.

The practical choice depends on whether the blade makes the opening, passes through a fixed panel or must reach a closed interior cut.

Opening type	What it represents	How to size it	Practical method	Main caution
Cutting kerf	The plywood is the workpiece being cut	Follow the full toothed path	Bandsaw or scroll saw	Support narrow offcuts
Static clearance passage	An installed panel lets the blade travel without being cut	Swept blade profile plus trial clearance	Scroll saw, jigsaw or router template	Keep every edge clear of the teeth
Access or threading slot	The blade reaches a closed interior shape	Full blade width to the internal cut	Scroll saw or jigsaw	Support the waste and relieve corners

Cut the slot without splitting the panel

For a narrow slot, a scroll saw can provide excellent control. Use a fine blade suitable for plywood, cut on the waste side of the line and allow the blade to reach the end without twisting. A wider opening is often quicker with a jigsaw and a drilled access hole, while a router and template produce smoother edges if the opening is large or its shape must be exact. In every case, secure the work with clamps and support the waste so its weight does not drag the cut closed.

Do not try to cut the new opening with the bandsaw running through that area. Isolate the power before fitting a panel around the blade, and remove the panel only if the manufacturer’s instructions permit it. If the plywood must remain around the blade, use an accessible scroll saw or another approved method with the bandsaw stationary. Attempting this operation with a moving blade can cut the operator’s hand, the panel or the machine’s guides.

Controlled relief cutting also helps when the slot contains an inside corner. The layered scroll-saw method demonstrates how shallow passes and separate waste sections can reduce force and prevent breakout. After cutting, leave the opening slightly oversize, remove the waste carefully and refine the edges with a file, rasp or sanding block. Vacuum the dust before test fitting, and seal exposed plywood edges if moisture resistance or a clean appearance matters.

Test the fit and refine the clearance

Before testing, disconnect the power and release blade tension only if the manual instructs you to do so. Fit the cardboard or ply gauge through the opening and move it through the blade’s full travel by hand. Check the narrowest point several times, including at different positions of the upper guide. The gauge should pass without force, but it should not be so loose that it cannot indicate contact.

A powered test should be brief and made at the lowest practical speed. Keep the guards fitted, stand clear of the blade path and watch the blade approach the panel from both sides. Never place a hand, loose glove or measuring rule beside moving teeth. If the blade rubs, remove the obstruction and determine whether the opening is narrow, the blade is deflecting or the gauge is inaccurate. Do not enlarge the slot simply to compensate for poor blade tracking or incorrect guide alignment.

Correct tension, tracking and guide settings according to the machine manual before changing the plywood. When more clearance is required, remove the panel and enlarge it evenly with a file, rasp or sanding block. Check the finished opening with the gauge again, ensuring the edges remain square and the panel retains enough support around the slot.

Finish the opening and work safely

A proper pre-cut check catches most blade-contact problems before they become damaged panels or torn teeth. Work through the following checks before making the final opening.

Before the cut

• Read the bandsaw manual and confirm which guards, guides and blade-clearance areas must remain in place.
• Inspect the blade for cracks, missing teeth and excessive wear, replacing it if necessary.
• Clamp the plywood and support narrow waste sections with a solid backing block.
• Wear eye and hearing protection, and use a suitable P2 dust mask when sanding or cleaning plywood.

Keep the final test controlled and avoid turning a clearance check into an improvised cutting job. The following checks apply while fitting and testing the opening.

During the test

• Isolate the power before reaching near the blade, moving a guide or adjusting the panel.
• Use a full-size scrap gauge rather than fingers to judge clearance.
• Keep hands, loose clothing and jewellery away from the blade and wheel.
• Run the machine briefly at low speed while watching the blade from a safe position.

Once the fit is satisfactory, sand any rough edges without changing the clearance, then vacuum inside the opening. Seal the plywood edges with a suitable clear finish or sealer where needed, and allow it to cure fully before the panel carries a load. Australian workshops should also ensure the bandsaw is connected to an appropriately earthed, RCD-protected circuit. Record the final opening dimensions, reinstall every original guard and keep the passage free of screws, offcuts and accumulated dust. A square opening with positive clearance, secure workholding and intact guarding gives the blade a clean path while keeping the operator safely outside the cutting line.