Fret Saw Blade Sizes and Types

Fret saw blades come in enough varieties that walking into a woodworking shop or browsing online can feel overwhelming. The numbers don't always mean what they seem to mean, different manufacturers use different naming systems, and the relationship between blade specifications and actual cutting performance isn't always obvious.

The specifications matter because they directly affect what you can cut, how fast you can cut it, and how the finished edge will look. Understanding what the numbers represent helps you match blades to specific tasks instead of guessing based on package descriptions or price points.

Teeth Per Inch Measurements

The most common way to specify fret saw blades is by teeth per inch, abbreviated as TPI. A blade marked 20 TPI has 20 teeth in every inch of blade length. The number tells you tooth spacing, which affects cutting speed and surface finish.

Lower TPI numbers mean coarser blades. A 12 TPI blade has larger teeth spaced farther apart than a 25 TPI blade. The larger teeth remove more material per stroke, which translates to faster cutting. The tradeoff is rougher surface finish. Each tooth takes a bigger bite, leaving deeper marks in the wood.

Higher TPI numbers mean finer blades. A 32 TPI blade has tiny teeth packed close together. Each tooth removes a small amount of material, so cutting progresses slowly. But the small bites leave a smoother surface that needs less sanding or cleanup afterward.

The TPI range for fret saw blades typically runs from about 10 to 32. Blades below 10 TPI are uncommon because they're too aggressive for the fine work fret saws are designed for. Blades above 32 TPI exist but are fragile and slow even by fret saw standards, reserved for extremely delicate work.

The TPI number alone doesn't tell you everything about a blade's performance. Tooth geometry, set angle, and blade thickness all interact with tooth count to determine cutting characteristics. But TPI is the starting point because it's the most visible and easily measured specification.

Blade Width and Kerf

Fret saw blade width typically ranges from about 0.015 to 0.025 inches. That's the measurement of the blade body thickness before accounting for tooth set. The width affects blade stiffness, minimum cutting radius, and kerf width.

Narrower blades flex more easily, which lets them navigate tighter curves. A 0.015-inch blade can follow a curve with a much smaller radius than a 0.025-inch blade. The flexibility comes from basic beam bending physics where resistance to bending decreases dramatically as thickness decreases.

Wider blades are stiffer and more stable for straight cuts or gentle curves. They're less likely to wander off your marked line and can handle more lateral pressure without deflecting. The increased stiffness comes at the cost of turning radius. Try to force a wide blade through a tight curve and it either breaks or cuts a wider radius than you intended.

The kerf is the width of the cut the blade makes. It's always wider than the blade body because the teeth are set alternately left and right to create clearance. A blade with 0.020-inch body width might cut a kerf of 0.025 to 0.030 inches depending on the tooth set. The extra width prevents the blade body from binding in the cut.

Kerf width matters when you're cutting expensive materials or working with patterns where every fraction of an inch counts. A wider kerf removes more material, which can affect fit when you're cutting joinery or inlay work. Knowing your blade's actual kerf width helps you account for material removal when marking cut lines.

Tooth Set Patterns

Tooth set refers to how the teeth are bent relative to the blade body. The most common pattern is alternate set, where each tooth bends slightly to one side, alternating left and right down the blade length. This creates the clearance that prevents binding.

The amount of set varies with blade coarseness. Coarser blades generally have more set because they need more clearance for the larger sawdust particles they produce. Finer blades have minimal set because they produce fine sawdust that doesn't require as much clearance space.

Some very fine fret saw blades have almost no set at all. The teeth are barely bent from the blade centerline, cutting a kerf only marginally wider than the blade body. These blades cut slowly and require careful technique to prevent binding, but they minimize material removal and leave very fine kerfs.

Skip tooth patterns exist where every other tooth is missing. This increases gullet size between teeth, which improves sawdust clearance. Skip tooth blades cut faster than standard patterns of the same TPI because the larger gullets let you apply more pressure without clogging the blade. The tradeoff is slightly rougher surface finish.

Reverse tooth patterns have a few teeth at the blade's bottom pointing upward instead of downward. These reverse teeth cut on the upstroke, which reduces tearout on the underside of your workpiece. Reverse tooth blades are more common in scroll saw applications but occasionally appear in fret saw blade offerings.

Blade Length Standards

Fret saw blades come in standard lengths, though the actual measurements vary between manufacturers. Common lengths include 5 inches, 5.5 inches, and 6.5 inches measured pin-to-pin or clamp-to-clamp.

The blade length needs to match your frame's throat depth and clamp position. A frame designed for 5-inch blades won't properly tension a 6.5-inch blade unless the frame is adjustable. Installing too-long blades in a fixed frame either prevents proper clamping or puts excessive stress on the frame.

Some fret saws have adjustable frames that accommodate multiple blade lengths. These frames use a sliding or telescoping mechanism that lets you adjust the distance between clamps. This flexibility means you can use broken blades by shortening the frame to match the remaining blade length.

Blade length affects throat depth in use. A longer blade mounted in a frame with the same physical dimensions gives you more working depth because more blade extends below the frame. This matters when cutting thick material or when you need to reach deep into a workpiece.

Material and Hardness

Most fret saw blades are made from spring steel or high-carbon steel. The steel needs to be hard enough to hold an edge through repeated cutting but not so brittle that it snaps from minor flexing. The balance between hardness and toughness defines blade performance.

Spring steel blades flex more before breaking, which makes them more forgiving for beginners or when cutting materials with varying density. The increased flexibility comes from the steel's composition and heat treatment. Spring steel tolerates bending stresses better than harder steels.

High-carbon steel blades are harder and hold edges longer but break more easily from lateral stress. These blades suit experienced users who maintain proper technique and want maximum cutting efficiency. The harder steel means less frequent blade changes due to dulling, but more frequent changes due to breakage.

Some specialty blades use tool steel or other alloys designed for specific applications. Blades intended for metal cutting might use harder steel formulations. Blades designed for abrasive materials might have carbide coating or diamond grit instead of traditional teeth.

The steel hardness is rarely specified on blade packages, but you can infer it from the intended use and price point. Economy blades typically use softer steel that dulls faster. Premium blades use harder steel with better heat treatment for longer edge life.

Pinned Versus Pinless Blades

Fret saw blades are pinless, meaning they have plain ends that fit into clamps. This distinguishes them from coping saw blades which have pins on each end. The pinless design is one of the defining characteristics of fret saw blades.

The lack of pins means the blade ends can be any thickness the clamps can grip. This allows for very fine blades that wouldn't have room for pins. It also means you can use scroll saw blades in many fret saw frames because scroll saw blades are also pinless.

The clamping mechanism needs to grip the blade securely enough to maintain tension during cutting. Most fret saw clamps use a screw or lever that presses the blade against a fixed surface. The clamping force must overcome the frame's spring tension without crushing the blade.

Some users struggle with blades slipping in the clamps, especially with very fine blades that have minimal surface area for the clamps to grip. Roughening the blade ends slightly with sandpaper or a file can improve grip. Some fret saws have serrated clamp faces that bite into the blade for better purchase.

Scroll Saw Blade Compatibility

Many fret saw users discover they can use scroll saw blades in their fret saw frames. Scroll saw blades are pinless and come in similar lengths, though the sizing systems differ slightly. This compatibility expands blade options significantly because scroll saw blades are widely available and come in extensive variety.

Scroll saw blades are categorized by number rather than TPI. A #5 scroll saw blade is moderately coarse, a #9 is very coarse, and a #2/0 is extremely fine. The number system doesn't directly translate to TPI but generally follows the pattern where higher numbers mean coarser blades and numbers with zeros mean finer blades.

The blade width and thickness vary with scroll saw blade numbers. A #5 blade might be wider and stiffer than a typical fret saw blade, which affects how it performs in a fret saw frame. The blade might work fine but feel different from purpose-made fret saw blades.

Some fret saw users prefer scroll saw blades for certain tasks. The wider variety of tooth patterns and the ability to get precise specifications make scroll saw blades attractive. The price is often comparable or lower than fret saw blades, especially when buying in bulk.

The main consideration is blade length. Scroll saw blades come in various lengths for different scroll saw models. You need to match the blade length to your fret saw frame's capacity, or use an adjustable frame that accommodates different lengths.

Tooth Geometry Variations

Beyond tooth count and set, the actual shape of each tooth affects cutting performance. Teeth can have different rake angles, gullet depths, and point shapes that influence how they remove material.

Standard tooth geometry on fret saw blades uses a moderate rake angle where the tooth face slopes back slightly from vertical. This angle affects cutting aggression and how the tooth engages the wood. A more aggressive rake angle cuts faster but requires more force and can cause tearout.

Some blades use a skip-tooth geometry where every other tooth is removed, creating larger spaces between cutting teeth. These larger spaces improve chip clearance and allow faster cutting because sawdust doesn't pack into the gullets as quickly. The cutting characteristics change noticeably with skip-tooth patterns.

Precision ground teeth appear on premium blades where each tooth is individually shaped for consistency. This manufacturing process costs more but produces blades where every tooth cuts identically. The consistent cutting action translates to smoother surface finish and more predictable blade behavior.

Milled teeth versus stamped teeth represent different manufacturing methods. Milled teeth are cut into the blade stock, while stamped teeth are formed by pressing. Milled teeth generally have more precise geometry but cost more to produce. Stamped teeth are adequate for most work and dominate the economy blade market.

Blade Stiffness and Thickness

Blade stiffness comes from both width and thickness. A blade that's 0.020 inches wide and 0.015 inches thick behaves differently from a blade that's 0.015 inches wide and 0.020 inches thick, even though both have similar cross-sectional areas.

The stiffness affects how the blade tracks through a cut. Stiffer blades resist deflection from grain variation or cutting pressure but can't navigate tight curves. More flexible blades follow curves easily but are more prone to wandering off the cut line in straight sections.

Thickness interacts with tooth set to determine actual kerf width. A thicker blade with minimal set might cut the same kerf width as a thinner blade with more set. The relationship isn't linear because tooth set depends on bending the tooth relative to blade thickness.

Some manufacturers specify blade thickness separately from width, while others only provide width measurements. When thickness isn't specified, it's usually similar to width for standard blades. Specialty blades might have different thickness-to-width ratios for specific applications.

Blade Packaging and Labeling

Blade packages rarely provide complete specifications. A typical package might list TPI and maybe blade length, but omit width, thickness, set amount, tooth geometry, and steel type. This incomplete information makes comparing blades between manufacturers difficult.

Some manufacturers use descriptive terms like "fine," "medium," and "coarse" instead of or in addition to TPI numbers. These terms are subjective and not standardized across brands. One company's "fine" blade might be equivalent to another's "medium" blade.

The package might indicate intended use like "for hardwood" or "for detail work" but these descriptions don't tell you what makes the blade suited to that purpose. You're left inferring that a blade marketed for hardwood probably has aggressive tooth geometry, but the actual specifications remain unclear.

Premium blades sometimes include more detailed specifications including blade dimensions, tooth count, set amount, and steel type. This information helps you understand what you're buying and make informed comparisons. But even premium packaging rarely includes everything you'd want to know.

The best approach is often to buy small quantities of different blades and test them in your actual work. The real-world performance tells you more than package specifications ever could. Over time you develop preferences for specific brands and types based on how they cut in your hands with your materials.

Number System Variations

The jeweler's saw gauge system uses numbers like 8/0, 6/0, 4/0, 2/0, 0, 1, 2, 3, up to 14. This system originated in metalworking and captures blade width, thickness, and tooth count in a single number. The finer gauges (higher numbers of zeros) are thinner and have more teeth per inch.

A 2/0 blade might have roughly 50 teeth per inch and measure 0.010 inches wide. A size 1 blade might have 30 teeth per inch and measure 0.015 inches wide. But these measurements vary between manufacturers, and the gauge number should be treated as relative rather than absolute.

Converting between jeweler's saw gauges and fret saw TPI isn't straightforward because the systems measure different characteristics. A jeweler's saw blade of a particular gauge might work in a fret saw frame, but you need to verify the blade length matches your frame and understand the blade's characteristics beyond just the gauge number.

Some fret saw blade manufacturers borrow the jeweler's saw numbering system for their finest blades. You might see fret saw blades listed as 2/0 or 3/0 alongside blades listed as 25 TPI or 30 TPI. This mixing of systems adds confusion but reflects the historical overlap between fret saws and jeweler's saws.

Specialty Blade Types

Spiral blades have teeth that spiral around the blade circumference rather than pointing in one direction. These blades cut in all directions, letting you rotate the workpiece or change cutting direction without turning the blade. Spiral blades are more common in scroll saw applications but exist for fret saws.

The spiral tooth pattern creates a wider kerf than straight-tooth blades of similar width. The teeth are cutting on all sides simultaneously, removing material around the entire blade circumference. This makes spiral blades aggressive cutters but limits their usefulness for precision work.

Double-tooth blades have two teeth together followed by a large gullet, repeating along the blade length. This pattern improves chip clearance and reduces vibration compared to standard tooth patterns. Double-tooth blades cut smoothly in many materials and are popular for scroll saw work.

Crown tooth blades have teeth that project from both edges of the blade, meeting at a ridge in the center. These blades cut a wide kerf and remove material aggressively. They're uncommon in fret saw applications but appear occasionally for specific cutting tasks.

Metal-cutting blades use different tooth geometry and harder steel than wood-cutting blades. The teeth are smaller and more numerous, with minimal set. These blades work in fret saw frames but cut slowly and are designed for softer metals rather than wood.

Blade Selection for Different Materials

Softwoods like pine cut easily with medium to coarse blades. A 12 to 18 TPI blade moves through softwood quickly and leaves an acceptable surface finish. The softer material doesn't dull blades quickly, and the lighter density means less resistance per stroke.

Hardwoods like oak, maple, and walnut require finer blades for clean cuts. An 18 to 25 TPI blade gives better results in hardwood, though cutting speed decreases. The denser material dulls blades faster and requires more strokes to achieve the same progress.

Plywoods and composite materials are abrasive and hard on blades. The glue layers in plywood dull teeth quickly, and the alternating grain directions in the plies cause tearout with coarse blades. Fine blades with 20 to 30 TPI work better in plywood despite the slower cutting speed.

Veneer is thin enough that blade thickness matters as much as tooth count. A fine blade in the 25 to 32 TPI range cuts veneer cleanly without splitting or tearing the thin material. The blade width should be narrow enough to navigate detailed curves common in veneer work.

Non-wood materials like plastics, composites, or thin metals require different blade considerations. Soft plastics can clog blade gullets, requiring skip-tooth patterns or frequent blade cleaning. Metals need specially designed blades with appropriate tooth geometry and hardness.

The Blade Life Reality

Fret saw blades dull gradually through use. The teeth lose their sharp points and the cutting efficiency decreases. In soft materials, a blade might cut cleanly for hours. In abrasive materials like MDF or particle board, a blade might noticeably dull after 30 minutes of cutting.

Recognizing a dull blade takes attention to how the saw feels. A sharp blade cuts with consistent resistance throughout the stroke. A dull blade requires more pressure, generates more heat, and produces rougher surface finish. The sawdust character changes too, from distinct particles to more powder as teeth dull.

Blade life depends on material, cutting technique, and blade quality. Economy blades dull faster than premium blades because the steel is softer. Aggressive cutting technique generates more heat, which accelerates dulling. Abrasive materials attack tooth edges directly.

Most users replace blades when cutting becomes noticeably harder rather than trying to measure tooth sharpness. Some people change blades proactively after a certain amount of cutting time. Others use blades until they break. The low cost of blades means replacement is often easier than trying to restore dulled blades.

Blade sharpening is theoretically possible but rarely practical. The teeth are so small that proper sharpening requires magnification and specialized files. The time investment exceeds the cost of a new blade for most users. Some manufacturers offer blade sharpening services but the shipping costs often exceed new blade prices.

Storage and Organization

Fret saw blades are thin and fragile, making storage important. Loose blades in a drawer tangle together and can bend or break. The packaging they come in is usually inadequate for long-term storage once opened.

Many woodworkers use small parts organizers with individual compartments for different blade types. Label each compartment with the blade specifications so you can grab the right blade without examining packages. This organization speeds up blade changes and helps you track which blades you have in stock.

Some people store blades in straws or small tubes to protect them from bending. Cut a straw to blade length, slide the blade in, and label the straw. This method works well but takes up more space than flat storage in compartments.

Magnetic strips can hold blades if mounted in a safe location where you won't accidentally brush against them. The magnetic force holds blades flat and visible, making selection easy. But exposed blades can catch on clothing or be knocked off the strip.

Whatever storage method you use, keeping blades organized by type saves frustration during projects. Nothing interrupts workflow like sorting through tangled blades trying to find the right TPI for your current cutting task.

Cost and Value Considerations

Blade prices vary widely. Economy blades might cost $3 to $5 for a pack of a dozen. Mid-range blades run $8 to $12 for a dozen. Premium blades can reach $15 to $20 for a dozen or more. The price differences reflect steel quality, manufacturing precision, and packaging quality.

The cheapest blades often have inconsistent tooth spacing, variable set amounts, and soft steel that dulls quickly. They work for rough cutting or learning, but the poor performance frustrates experienced users. The low price is offset by how quickly the blades dull or break.

Premium blades cost more but cut better and last longer. The precise manufacturing produces blades where every tooth cuts identically. The harder steel maintains sharpness through more cutting time. The improved performance often justifies the higher price for serious woodworkers.

Buying blades in bulk reduces per-blade cost if you've found types you like. Some suppliers offer packs of 50 or 100 blades at significant discounts compared to dozen packs. Bulk buying makes sense once you know which blades suit your work.

The value calculation depends on your usage. If you're cutting occasionally, economy blades might be fine despite their limitations. If you're cutting regularly or working on important projects, premium blades deliver better results and less frustration. The cost difference becomes small when spread across the improved cutting performance.

The Practical Reality

Understanding blade specifications helps you make informed choices, but experience teaches you more than charts and numbers. Two blades with identical specifications from different manufacturers can cut differently because of variations in tooth geometry, steel quality, and manufacturing precision that aren't captured in the basic measurements.

The best approach is treating blade specifications as starting points. A 20 TPI blade will generally behave like a 20 TPI blade, but the specific performance depends on factors beyond tooth count. Try different brands and types in your actual work to find what performs well in your hands with your materials and your fret saw frame.

Over time you develop preferences for specific blade types for specific tasks. You might prefer one brand's 25 TPI blade for hardwood and a different brand's 18 TPI blade for softwood. These preferences develop through use, not through studying specifications on packages.

The blade specifications provide a vocabulary for discussing and comparing blades, but the real information comes from putting blades in your saw and cutting wood. The specifications tell you what you're buying. The cutting tells you whether it's any good.