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Introduction
Laser-welded diamond saw blades are the go-to choice for cutting tough materials like concrete and asphalt. In these blades, diamond segments (the “teeth”) are laser-welded to a steel core, creating a strong bond. This guide will walk you through everything you need to know – from how they’re made, to technical specs, to choosing the right blade for different jobs.
At Johnson Tools, we manufacture a wide range of laser-welded blades and are here to help you understand their features. If you have any questions, feel free to visit our homepage or contact us.
How Laser-Welded Blades Are Made
Making a laser-welded diamond blade involves several key steps. First, metal powders and diamond grit are pressed and sintered into hard segments. These segments are then laser-welded one by one onto the steel blade core. After welding, the blade is finished by polishing, painting, and sharpening (grinding the segment edges slightly so diamonds are exposed). Every segment weld is tested to ensure it holds strong under cutting stress. The result is a laser-welded blade with durable diamond teeth that won’t easily break off, even when cutting dry or under heavy load.
Blade Core and Slot Types
The core of a diamond blade is the circular steel disc that holds the segments. Cores are made from high-alloy, heat-treated steel designed to handle stress and heat. They often use different alloy formulations depending on blade size – for instance, smaller diameter blades use a chromium-molybdenum steel, while very large blades use a tougher manganese-alloy steel for extra stiffness.
Slots (Gullets) are the cutouts in the core between segments. They help remove debris and cool the blade. Common slot designs include:
- Key Slots: Straight, narrow slots (like a key shape). Often used for hard stone (granite) blades and many general-purpose blades. They strike a balance between cooling and maintaining core strength.
- Narrow U-Slots: Thin U-shaped cutouts. Found on marble blades, early-entry green concrete blades, and some silent-core blades. They provide good debris removal while keeping the blade quieter (less air noise).
- Wide U-Slots: Broad U-shaped cutouts. Typical for blades on very abrasive materials like asphalt and uncured concrete. The wide gullet clears out dust and slurry quickly, preventing the blade from binding in soft materials.
Each slot type is a design choice balancing cooling and stability. Wider slots remove debris faster but leave less metal in the core (slightly reducing strength), whereas narrower slots or key slots leave more steel for rigidity.
Below is a quick comparison of common slot styles and their typical use:
| Slot Type | Appearance/Shape | Common Use Cases |
|---|---|---|
| Key Slot | Straight slot (“keyhole” shape) | Asphalt, green concrete, and other highly abrasive materials |
| Narrow U | Thin U-shaped slot | Marble, early-entry green concrete (Soff-Cut), silent cores |
| Wide U | Wide U-shaped slot | Asphalt, green concrete, other highly abrasive materials |
Figure: Diagram of a diamond blade structure, showing the steel core (disc), laser-welded diamond segments (teeth), and the gullets (slots) between segments. The arbor hole at the center mounts the blade on the saw.
Arbor Holes and Blade Mounting
The arbor hole is the center hole that mounts the blade on your saw. Common diameters include 22.23 mm (7/8″) for many handheld grinders and 25.4 mm (1″) for most walk-behind saws. Some other saws use 20 mm or even larger 50–60 mm arbors (as on big wall saws). If a blade’s arbor is larger than your saw’s spindle, you can use adaptor bushings to ensure a snug fit.
A few blades have non-standard arbor shapes. For example, some small saws use a diamond-shaped arbor, and early-entry green concrete saws use a triangular arbor (the Husqvarna Soff-Cut system). These specialized blades usually come with matching adapters or require specific saws. Additionally, certain blades feature two small pin holes near the center – these accommodate drive pins on some machines to prevent the blade from spinning free.
Segment Bond Hardness and Performance
Not all diamond segments are the same. The metal bond (the mixture of metals that holds the diamonds) can be formulated to be softer or harder, which affects how the blade cuts and wears:
- Soft bond segments wear down faster, exposing new diamonds quickly. They excel at cutting hard, less abrasive materials (like cured concrete or granite) because the material doesn’t remove much bond on its own. A softer bond ensures the blade stays sharp, though it means a shorter blade life.
- Hard bond segments wear more slowly. These are used for very abrasive, softer materials like asphalt or green (uncured) concrete. The abrasive material would grind away a soft bond too fast, so a harder bond is needed to make the blade last. (If you use a hard-bond blade on hard concrete, it may glaze over and cut poorly, because the bond isn’t wearing to expose fresh diamonds.)
Manufacturers typically label bonds from very soft up to very hard, corresponding to the material type (for example, asphalt blades use hard bonds, while cured concrete blades use softer bonds).
Segment Types and Dimensions
The shape and size of the segments themselves can vary, and each design has its purpose:
Most diamond blades use flat rectangular segments – this shape is tried-and-true and works for general-purpose and road saw blades. In some special cases (for example, certain wall saw blades), a differently shaped segment might be used, such as a “U-shaped” or stepped profile, to aid cutting performance or debris removal. There are even wavy or curved segment designs, but these are uncommon and typically only made on request. Flat segments remain the industry standard for their reliability.
Segment Thickness vs. Core Thickness: It’s important that the segments are slightly thicker than the blade’s core. This ensures the cut (kerf) is wider than the core, preventing the steel disk from rubbing on the material. For blades up to about 600 mm (24″) in diameter, the segments are typically ~0.8–1.0 mm thicker than the core. For very large blades (over 600 mm), segments are about 1.5–2.0 mm thicker than the core.
For example, a 350 mm blade might have a 2.8 mm core and 3.6 mm segments (≈0.8 mm difference). A 900 mm blade could have a 4.5 mm core with 6.0 mm segments (≈1.5 mm difference). Having the right difference in thickness protects the core and avoids the blade getting stuck.
(Certain specialty blades like tuck-pointing blades or loop blades may not follow these rules, as they have unique designs.)
Below is a quick reference table on segment vs core thickness:
| Blade Diameter | Segment Thickness vs Core |
|---|---|
| 105 mm – 600 mm (4″–24″) | Segment ~0.8–1.0 mm thicker than core |
| >600 mm (24″+) | Segment ~1.5–2.0 mm thicker than core |
| Wall saw blades >600 mm | Segment ~1.3–1.5 mm thicker (for rigidity) |
| Stone saw blades ~1000 mm | Segment ~1.5–2.0 mm thicker (standard) |
Protective Teeth (Undercut Protection)
Cutting abrasive materials (like asphalt or uncured concrete) can wear away a blade’s steel core at the segment joints – a phenomenon called undercutting. To prevent this, manufacturers add protective teeth to asphalt and green concrete blades. These protective elements come in two main forms: small tungsten carbide teeth brazed onto the core, or extra drop segments (lower diamond segments placed between the main ones). Both types act as sacrificial guards that take the abrasive wear instead of the core.
Protective teeth are spaced symmetrically around the blade (for example, a 350 mm blade might have 3–4, a 600 mm blade ~7). They usually sit about 3 mm taller than the regular segments – enough to shield the core. For high-speed or high-horsepower saws, taller 5 mm protective teeth are used for extra protection.
Choosing the Right Blade for the Job
Diamond blades are often labeled by what they cut. Here’s a quick rundown of the main types and their typical features:
- General Purpose Blades: These are meant to handle a bit of everything – concrete, brick, stone, etc. Because they’re not specialized, they won’t cut as fast as a material-specific blade. General-purpose blades often have key slots or narrow U-slots for cooling.
- Stone Blades: Designed for natural stone like marble, granite, limestone, and sandstone. They typically have bonds formulated for mineral hardness, and usually feature key or narrow U slots to keep the cut clean in these brittle materials. They are often used wet to minimize chipping.
- Concrete Blades: Made for cured, dry concrete (and they also work well for masonry like brick or block). These blades use a softer bond (since concrete itself is hard) and may have medium or narrow gullets. Many general construction blades fall in this category and might simply be called a concrete saw blade.
- Green Concrete Blades: For cutting control joints in new concrete (within the first day or two of curing). These blades have a hard bond to withstand the abrasive “green” concrete. They commonly feature wide U-slots to quickly remove slurry. Some are even designed for early entry cutting within a few hours of finishing the slab (e.g., for the Soff-Cut system).
- Asphalt Blades: Made specifically for asphalt (a very soft, abrasive material). These have the hardest bonds and almost always include protective teeth (drop segments or carbide inserts) because asphalt would otherwise undercut the blade quickly. They usually have wide gullets to clear out asphalt debris. This is why an asphalt cutting blade is quite different from a typical concrete saw blade in its bond and design.
- Heavy-Duty Blades: For demanding jobs like cutting heavily reinforced concrete or thick road pavement, specialized blades are used. These are matched to the saw’s power and material. A wall saw blade for a 35 HP hydraulic unit will have a different bond than one for a smaller 5 HP electric saw. Road cutting blades (for asphalt-over-concrete roads) often use medium-hard bonds and feature wide slots and protective segments to handle the mix of materials.
Conclusion
Remember to pick a blade that matches your material – the bond and design make a big difference. Keep an eye on features like protective teeth for abrasive jobs.
If you’re unsure or have questions, feel free to reach out to us. Check out our homepage for our product range, or contact us directly through our contact page.
