Why Fret Saw Blades Come in 47 Sizes (And Most Woodworkers Only Need Three)

Pull up any fret saw blade supplier's catalog and you'll find something like 47 different offerings. Sizes numbered in a system borrowed from jewelers that runs backward - 8/0 is the finest, size 12 is the coarsest. TPI counts from 10 to beyond 50. Widths from 0.010 inches (roughly two human hairs) to 0.024 inches. Skip tooth, reverse tooth, spiral, double tooth, precision ground, crown cut.

It's an absurdly crowded product category for a hand tool that most people can't even identify on sight.

The catalog makes no sense until you realize it's not one market. It's two completely different woodworking traditions that happen to buy their blades from the same suppliers - and they barely overlap.

The Two Traditions

One tradition is scroll work. Decorative fretwork, marquetry, inlay, the kind of ornamental cutting that turns thin wood into lace. This crowd lives in the finest sizes: 2/0 through 6/0, blades so thin they're measured in thousandths of an inch, with TPI counts in the 40s and 50s. They cut slowly, deliberately, following intricate patterns through veneer and sheet goods rarely thicker than a quarter inch. Blade breakage is constant - the hair-thin steel snaps from the slightest twist - and they buy blades by the gross because going through a dozen in a single session isn't unusual.

The other tradition is joinery. Specifically, hand-cut dovetails. When you need to remove waste from between dovetail pins, the fret saw turned out to be the perfect tool by pure accident - its thin blade fits in the kerf left by the dovetail saw, and the deep frame clears the workpiece. This crowd lives in sizes 1 through 5, moderate blades with 15 to 25 TPI. They cut hardwood up to an inch thick. They need durability, not delicacy.

Between these two groups, you account for about 90% of all fret saw blade sales. The other 47 sizes in the catalog? Specialty applications, metalworking crossovers from the jeweler's saw world, and legacy products that exist because someone ordered them once in 1987 and they never left the catalog.

The Numbering System Nobody Designed

The size numbering comes from jewelers, who've been using fret-type saws for metalwork since the 1800s. The system runs from 8/0 (the finest) through 0, then 1 through 14 (the coarsest). Each number roughly corresponds to a combination of blade width, thickness, and tooth count - but "roughly" is doing heavy lifting in that sentence.

A size 2/0 blade from one manufacturer might be 0.011 inches wide with 51 TPI. From another manufacturer, the same "2/0" might be 0.012 inches wide with 48 TPI. The numbering system is a guideline, not a specification. Nobody standardized it because it emerged from craft tradition rather than engineering committees.

The TPI measurement is more concrete - 20 teeth per inch means 20 teeth per inch regardless of manufacturer. But TPI alone doesn't tell you how the blade cuts, because tooth geometry varies wildly. Skip-tooth blades have every other tooth removed for better chip clearance. Reverse-tooth blades have a few bottom teeth pointing upward to reduce tearout on the workpiece's underside. Precision-ground blades have individually shaped teeth that cost more and cut cleaner than stamped teeth. Two blades with identical TPI can feel completely different in the cut.

What Three Blades Actually Cover

Ask experienced fret saw users what they keep in the drawer and you get remarkably consistent answers.

A size 1 or 2 (15 to 20 TPI) for general joinery work. Stiff enough to handle hardwood without wandering, fine enough to leave a clean surface that needs minimal cleanup. This is the dovetail blade, the go-to for joinery waste removal, the size that gets replaced most often because it does the most work.

A size 2/0 or 3/0 (around 40 TPI) for fine scroll work and tight curves. The thin blade navigates radii that the general-purpose blade can't follow. Cuts slowly. Breaks frequently. But for detailed ornamental work in thin stock, nothing else fits.

A size 5 or 7 (10 to 15 TPI) for thicker stock and aggressive curves. Coarser teeth clear waste faster and survive harder woods better. The surface finish is rougher, but when you're hogging out waste rather than making a show surface, speed matters more than smoothness.

Three blades. The other 44 offerings in the catalog exist for edge cases, specialty applications, and the natural tendency of any craft-supply market to fill every possible niche whether real demand exists or not.

The Breakage Economy

Fret saw blades are disposable. Not in the way that cordless drill bits are disposable - you use them until they dull and replace them. Fret saw blades are disposable in the way guitar picks are disposable. They snap from normal use, regularly, and the cost of replacement is built into the economics of using the tool.

A dozen blades costs $5 to $15 depending on quality. An aggressive scroll work session can burn through six blades in an hour. The joinery crowd breaks fewer - maybe one or two per session - because they use sturdier sizes and apply less lateral pressure. Either way, the per-blade cost runs well under a dollar, and experienced users buy in bulk the way woodworkers buy sandpaper: not by the piece, but by the box.

The breakage pattern also varies by tradition. Scroll workers break blades from twist - the thin blade can't handle the rotational stress of following tight curves under any lateral pressure. Joinery workers break blades from flex - pushing a stiff blade through thick hardwood bends it past its elastic limit. Same tool, same consumable, completely different failure modes from completely different working methods.

Why the Catalog Stays Full

Blade manufacturers keep all 47 sizes in production for the same reason hardware stores stock 15 varieties of wood screw: the overhead of maintaining the product line is tiny compared to the cost of losing the one customer who needs a size 4/0 spiral-tooth blade for cutting mother-of-pearl inlay.

The craft supply market rewards completeness. A supplier with every size gets the orders from the marquetry artist AND the dovetail cutter AND the jeweler doing metalwork AND the luthier cutting rosettes. Dropping the sizes that sell three packs a year risks losing the customer who buys everything else alongside them.

And so the catalog persists, a fossilized record of every niche application that ever generated a purchase order. Two living traditions - scroll art and joinery - sustaining a product ecosystem that serves dozens of use cases, most of which barely exist anymore. The numbering system borrowed from Victorian-era jewelers. The specialty types that serve metalworkers, instrument makers, and hobbyists in quantities that would embarrass any product manager thinking in volume terms.

Forty-seven sizes. Three that matter. And a supply chain cheerfully maintaining the other 44 because in the world of craft tooling, you never know who's going to need a 6/0 precision-ground reverse-tooth blade at 2 AM on a Sunday.