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ISO 25157:2013 — Diamond Segments for Circular Saw Blades, Frame Saws, and Core Drills
Specifications, Tolerances, and Classification of Diamond Cutting Tools for Natural Stone
1. Scope and Purpose of ISO 25157:2013
ISO 25157:2013 establishes the dimensional specifications, tolerances, and classification system for diamond segments used in circular saw blades, frame saw blades, and core drill bits for natural stone and construction material processing. Diamond segments are the cutting elements consisting of diamond grits embedded in a metal matrix bond system, which are brazed or laser-welded onto steel cores to form the complete cutting tool.
The global stone processing industry consumes over 500 million carats of industrial diamond annually, with diamond segment tools accounting for approximately 70% of all natural stone cutting operations worldwide. Standardized segment dimensions enable interchangeability between manufacturers and consistent tool performance.
The standard covers both sintered and electroplated diamond segments, specifying dimensional tolerances for length, width, height, and thickness. It also defines the classification code system that conveys information about segment type, bond hardness, diamond concentration, and intended application, enabling users to select the appropriate tool for specific stone types and processing conditions.
| Segment Dimension | Tolerance Fine (mm) | Tolerance Normal (mm) |
|---|---|---|
| Length (up to 40 mm) | +/-0.3 | +/-0.5 |
| Width (segment) | +/-0.2 | +/-0.4 |
| Height (segment) | +/-0.3 | +/-0.6 |
| Thickness (segment) | +/-0.15 | +/-0.3 |
| Arc length deviation | +/-0.4 | +/-0.8 |
2. Manufacturing Processes and Quality Parameters
The performance of diamond segments is governed by three primary variables: diamond grit size and quality, metal bond composition, and sintering parameters. The metal bond (typically cobalt-based, bronze-based, or iron-based) serves to hold diamond crystals in place while being gradually eroded during cutting to expose fresh diamond cutting edges. This self-sharpening mechanism is fundamental to the tool’s cutting efficiency.
Bond hardness selection is arguably the most critical design decision. A bond that is too hard relative to the stone being cut will not erode sufficiently to expose new diamond grits, resulting in a glazed tool surface and dramatically reduced cutting speed. Conversely, a bond that is too soft wears away too quickly, wasting diamond and shortening tool life.
The standard specifies quality control testing methods including segment hardness testing (Rockwell B or equivalent), dimensional verification using calibrated gauges, and visual inspection for cracks, voids, and bond uniformity. For sintered segments, density measurement provides an indirect quality indicator, with theoretical density typically reaching 96-99% in well-manufactured products.
Modern manufacturing advances include the use of additive manufacturing (3D printing) for bond matrix fabrication, enabling functionally graded bond structures with optimized wear profiles. Laser welding technology has largely replaced brazing for segment attachment in high-safety applications, offering joint strengths exceeding 400 MPa and eliminating environmental concerns associated with silver brazing fluxes.
3. Engineering Applications and Design Insights
The selection of diamond segments for a given application requires balancing multiple performance factors including cutting speed, tool life, surface finish quality, and power consumption.
Application-Specific Design Considerations
- Granite cutting: Requires hard bond matrices (HRB 105-115) with fine diamond grit (40/50 to 50/60 US mesh) at medium concentration. The high quartz content of granite (25-60%) severely abrades the bond, necessitating maximum wear resistance.
- Marble cutting: Uses soft bond matrices (HRB 85-95) with coarser diamond grit (30/40 to 40/50 US mesh). Marble’s lower abrasiveness allows faster bond erosion and requires larger chips for efficient material removal.
- Concrete cutting: Employs medium bond hardness (HRB 95-105) with a wider diamond grit distribution to handle aggregate heterogeneity. Segmented rim designs with gullet depths of 15-25 mm provide chip clearance.
Operating diamond segment tools at inappropriate peripheral speeds (outside the recommended 25-45 m/s range for most stone applications) can cause thermal damage to the diamond crystals. At temperatures above 700 C, diamond begins to graphitize and loses its cutting hardness. Adequate water cooling (5-15 L/min per blade) is essential for maintaining segment temperature within safe limits.
4. FAQs
Q: What does the diamond concentration number in the classification code mean?
A: The concentration code in ISO 25157 follows the traditional scale where 100 concentration corresponds to 4.4 carats/cm3 of diamond in the segment volume. Common values range from 30 (light concentration for soft materials) to 120 (heavy concentration for hard, abrasive materials).
A: The concentration code in ISO 25157 follows the traditional scale where 100 concentration corresponds to 4.4 carats/cm3 of diamond in the segment volume. Common values range from 30 (light concentration for soft materials) to 120 (heavy concentration for hard, abrasive materials).
Q: How do I determine if a diamond segment is suitable for wet or dry cutting?
A: Segments designated for dry cutting have wider gullet spacing and bonds formulated to dissipate heat through air cooling. Wet-cut segments assume continuous water cooling and use bonds optimized for lower operating temperatures. Using a wet-cut segment dry can cause rapid bond degradation and diamond loss within minutes.
A: Segments designated for dry cutting have wider gullet spacing and bonds formulated to dissipate heat through air cooling. Wet-cut segments assume continuous water cooling and use bonds optimized for lower operating temperatures. Using a wet-cut segment dry can cause rapid bond degradation and diamond loss within minutes.
Q: What is the typical lifespan of a diamond segment in stone cutting?
A: Segment life varies enormously with material: from 50-100 m2 per blade in high-silica granite to 500-1000 m2 in soft limestone. Proper matching of bond hardness to stone type is the single most important factor affecting tool life.
A: Segment life varies enormously with material: from 50-100 m2 per blade in high-silica granite to 500-1000 m2 in soft limestone. Proper matching of bond hardness to stone type is the single most important factor affecting tool life.
Q: Are tungsten carbide segments covered by this standard?
A: No, ISO 25157 applies only to diamond-impregnated segments. Tungsten carbide tool tips for stone cutting are covered under separate standards (ISO 513 and ISO 1832 for indexable inserts).
A: No, ISO 25157 applies only to diamond-impregnated segments. Tungsten carbide tool tips for stone cutting are covered under separate standards (ISO 513 and ISO 1832 for indexable inserts).
