How to Cut Internal Shapes on a Band Saw with Relief Cuts
What's inside
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Relief cuts make a band saw much more capable at cutting curves, especially concave curves and internal openings that would otherwise pinch the blade. The basic idea is simple: remove waste in small sections so the blade is never forced to turn sharply while also carrying a large amount of material.
There is one important limitation. Relief cuts help with an opening connected to the edge of a board, but they do not magically let a standard welded band saw blade start in the middle of solid wood. For a completely enclosed internal shape, you need a drilled entry hole and a way to thread the blade through it, or you must cut into the shape from an edge and repair the opening afterward.
Contents
Choose the right blade first
Blade width and tooth pitch determine how tightly the saw can turn and how cleanly it cuts. A narrow blade follows tighter curves, while a wider blade tracks straighter and is less likely to wander. For most small internal shapes in stock up to about 1 inch thick, a 1/4-inch or 3/8-inch blade is a useful starting point. A 1/4-inch blade can handle tighter curves, but it is easier to twist or break if you force it.
| Workpiece and cut | Practical blade choice | Main trade-off |
|---|---|---|
| Thin plywood, small tight curves | 1/8- to 1/4-inch blade, 6-10 TPI | Turns tightly but cuts slowly and can wander |
| Hardwood up to about 1 inch | 1/4- to 3/8-inch blade, 4-6 TPI | Good control without excessive clogging |
| Thick stock or mostly straight relief cuts | 1/2-inch blade, 3-4 TPI | Tracks well but needs a larger curve radius |
Use a blade with at least two or three teeth in the material at all times. A blade with too many teeth packs with sawdust and overheats; too few teeth can grab the work and leave a rough, uneven cut. If you regularly cut curves, a selection of wood-cutting band saw blades is more useful than trying to make one general-purpose blade do everything.
Lay out the shape and relief cuts
Draw the finished opening full size on the workpiece. Mark the waste side clearly, then identify every concave section where the blade would need to turn more tightly than its natural curve allows. Relief cuts should run from the waste area into the layout line, stopping just short of the finished line.
Space the cuts more closely around tight curves. As a practical guide, use relief cuts every 1/2 to 1 inch on moderate curves and every 1/4 to 1/2 inch on tight curves. On thick hardwood, closer spacing reduces the amount of wood each cut must release. Do not cut through the finished line: stopping approximately 1/16 inch away leaves enough material for controlled cleanup.
For a shape with an opening connected to the edge, make the relief cuts first. They divide the waste into small fingers or wedges. When the main cut reaches one of these cuts, the waste falls away instead of trapping the blade.
Make the cuts safely
Set the upper blade guide just above the workpiece, normally within 1/8 inch. Check that the blade is sharp, properly tensioned, and tracking in the center of the tires. A dull blade encourages pushing, which is the quickest way to twist a narrow blade or burn the wood.
Start the saw before bringing the workpiece to the blade. Feed steadily, but do not force the cut. Make the relief cuts with the work supported flat on the table. For deep stock, keep both hands to the sides of the blade and use a push block or auxiliary handle when your fingers would approach the cutting path.
Cut the relief slots from the waste side toward the layout line. Stop at the marked stopping point and back the workpiece away without turning it while the blade is still engaged. Turning in a partial slot can pinch the blade. A band saw blade can usually tolerate a straight withdrawal, but it does not tolerate being twisted sideways.
After the relief cuts are complete, follow the finished outline with the smallest practical amount of pressure. Let each waste section separate before moving into the next part of the curve. If the blade begins to deflect, stop and add another relief cut rather than trying to steer harder.
Handling a fully enclosed opening
A standard band saw uses a continuous welded blade. To cut a completely enclosed shape, drill an entry hole through the waste, remove the blade from the wheels, pass it through the hole, and reinstall it. That requires removing and reinstalling the blade, and the blade must be opened and rewelded if it is a permanently welded loop. Most home workshops do not have a reliable blade-welding setup.
Use an entry hole at least slightly larger than the blade’s widest dimension, commonly 3/8 to 1/2 inch for small work. Drill inside the waste, not on the finished line. A Forstner bit leaves a clean hole, but a standard twist bit is fine when the hole will be hidden. A Forstner bit set is worth buying if you make many internal cutouts.
For occasional enclosed openings, the cheaper and simpler option is often a drill press followed by a jigsaw or scroll saw. A scroll saw for internal woodworking cuts accepts a blade through a drilled hole and is designed for this operation. A jigsaw works too, though it is harder to keep perpendicular in thick stock.
Clean up and avoid common failures
Leave the final 1/16 inch for a flush-trim bit, rasp, file, or sanding drum. If the opening must be precise, make a full-size template and use the band saw only to remove most of the waste. Check the result with calipers at several points; a cut can look symmetrical while being several millimeters off.
The most common failures are blade drift, burning, and a pinched blade. Drift usually means the blade is dull, poorly tensioned, or the work is being forced. Burning indicates too slow a feed, too many teeth per inch, or resin buildup. A pinched blade usually means the relief cuts are too far apart. Stop the saw before attempting to free a trapped workpiece, and never pull backward while the blade is moving.
Relief cuts are inexpensive and effective. They let a properly adjusted band saw cut complex edge-connected shapes cleanly, but they cannot replace the internal-cutting capability of a scroll saw or jigsaw when the opening is fully enclosed.
