Even though balsa is technically a hardwood -- it has broad leaves instead of needles like conifers -- it remains famous for it's reputation as the softest wood available. Balsa is a native to Mexico, Brazil and Bolivia, and is readily available domestically. It's not considered strong, but it's easy to cut and work with.
The Janka Scale
Balsa is the softest commercially available wood. It ranks only 90 to 100 on the Janka hardness scale, which is the go-to scale for wood density worldwide. Red oak, for example, one of the most common domestic hardwoods on the Janka scale, ranks 1,290.
The softness of balsa lends itself to crafting, models, lightweight cases, fishing lures and, because of it's exceptional tonal qualities, musical instrument bodies. The techniques used to cut balsa include cutting larger pieces with power equipment, and thinner pieces by hand with sharp knives.
Sharp Blades Only
Because of it's softness, use only the sharpest tools to cut balsa thicker than about 1/4 inch. Hardened steel blades are acceptable if they're new, or have recently been sharpened. Carbide-tipped blades are best, simply because they hold a sharp edge longer than hardened or high-speed steel.
You can use anything you like to cut balsa, however using anything other than sharp tools will result in burning, or a fuzzy, rough cut.
Saw Blade Type
Use hollow-ground, or cabinetmaker's blades for the best cuts on balsa. Never use rip blades. This type of blade is too aggressive and results in chipping and splintering. Recognize hollow-ground or cabinetmaker's blades by square, flat teeth. Recognize rip blades by jagged, pointed teeth that tip back and forth in an alternating fashion.
Band and Scroll Saw Blades
Band saw and scroll saw blades are defined by tooth count, the higher the tooth count, the cleaner the cut. The thickness of the balsa also comes into play. Cut 1/4-inch balsa with blades that have at least 12 to 14 teeth per inch.
It's typically necessary to use lower tooth counts of about 10 for balsa thicker than 1/2 inch. If the balsa begins to burn, smoke or resist your efforts to cut it, it may be necessary to switch to a lower tooth count.
Crafting Thin Balsa
One of the most common cuts on 1/4-inch or thinner balsa is done by hand with a utility or craft knife. But the way you use it makes a difference.
Step 1: Establish Your Lines
Use a template, or draw a pattern freehand on 1/8 or 1/4-inch-thick balsa.
Step 2: Proper Knife Position
Hold the tip of the knife at 45 degrees to the wood. Apply light pressure to the knife. Make the first cut perpendicular to the grain only. When the pattern begins to turn parallel with the grain, stop cutting.
Step 3: Work Across the Grain
Move the knife on the pattern, making all other initial cuts perpendicular to the grain.
Don't attempt to cut through the balsa on the first pass. It requires multiple passes.
Step 4: Join the Lines
Cut the remaining parallel lines, to join up with the perpendicular cuts, to finish the first cut or outline of the pattern. The initial cut should be no deeper than about 1/32 inch.
Step 5: Repeat the Process
Repeat the cutting process as many times as needed until the knife passes through the pattern and releases it.