Circular Saw Blade Testing

Circular saw blade inspection mainly conducts scientific testing and analysis on the dimension and geometric precision testing, tooth profile and tooth tip parameter testing, matrix property testing, welding/brazing quality testing, surface and coating testing, and static balance and dynamic balance testing, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Dimension and geometric precision testing: The key dimensions such as the outer diameters, bore diameters and thicknesses of the circular saw blades, as well as the geometric precision such as the radial runout, face runout and flatness are tested. These parameters directly affect the installation matching and rotation stability of the saw blades, and are the basis of ensuring the cutting precision and safe operation. The testing tolerances are usually carried out according to the relevant national standards or manufacturer technical specifications.

Tooth profile and tooth tip parameter testing: The geometric angles such as the rake angles, clearance angles and wedge angles of the saw teeth, as well as the parameters such as the tooth pitches, tooth heights and gullet volumes are tested. The tooth profiles determine the cutting performance, chip removal ability and durability of the saw blades. The precise measurement of the sharpness, symmetry and whether there are the defects of the tooth tips is the key link of guaranteeing the sawing efficiency and kerf quality.

Matrix property testing: The mechanical property testing such as the hardness, tensile strength, yield strength and impact toughness is carried out on the saw blade matrices. The matrices are the skeletons of the saw blades, and their material properties and heat treatment states determine the overall rigidity, deformation resistance and fatigue resistance of the saw blades, especially crucial under the heavy-load or intermittent cutting conditions.

Welding/brazing quality testing: For the tipped saw blades (cemented carbide teeth, diamond teeth, etc.), the welding (or brazing) strengths between the teeth and the matrices need to be tested. Through the methods such as the visual inspection, colour penetrant or ultrasonic flaw detection, whether the solder layers are uniform and whether there are the defects such as the blowholes, slag inclusions, cracks and false welding are checked, ensuring that the teeth do not fall off during the high-speed cutting.

Surface and coating testing: The surface finish of the saw blade matrices and teeth, and the uniformity, adhesion and thicknesses of the anti-rust coatings (such as the bluing and nickel plating) or anti-friction coatings (such as the titanium nitride) are checked. The good surface treatments can reduce the friction heat, prevent the chip adhesion and reduce the corrosion, thereby extending the saw blade lives.

Static balance and dynamic balance testing: The static unbalance amounts and dynamic unbalance amounts of the saw blades are determined through the balancing machines. The unbalance will cause the severe vibrations of the saw blades during the high-speed rotation, which not only affects the machining precision and surface qualities, but also accelerates the wear of the spindle bearings and even causes the safety accidents. It is the core testing item of the high-speed saw blades.

Material metallographic structure analysis: The samples are taken from the saw blade matrices and tooth materials for the metallographic analysis, observing their micro-structures (such as the grain sizes, carbide distributions and martensite morphologies), to evaluate whether the heat treatment processes of the material are proper, thereby judging their comprehensive mechanical properties and service lives.

Testing Scope

Woodworking circular saw blades: Covering the alloy saw blades, diamond saw blades and frame saw blades used for the processes such as the ripping, crosscutting and grooving. The testing focuses on the tooth profile sharpness, resin adhesion resistance, matrix tensions and the dynamic balance properties under the high-speed rotation, ensuring their cutting efficiencies and safety at the high rotation speeds.

Metal cutting circular saw blades: Including the cold saw blades, friction saw blades and cut-off saw blades. The testing emphases are the high-temperature strengths and toughness of the matrices, the hardnesses and red hardnesses of the saw teeth, the welding strengths, as well as the deformation resistance of the saw blades when bearing the huge radial forces.

Stone/concrete cutting saw blades: Mainly referring to the diamond circular saw blades. The testing scope includes the matrix wear resistance of the diamond segments, diamond concentrations and particle sizes, the welding strengths between the segments and the matrices, as well as the flatness and tension states of the matrices, to adapt to the harsh working conditions with the high abrasion and high impacts.

Plastic and composite material cutting saw blades: The special saw blades for cutting the materials such as the acrylic, PCB and carbon fiber. The testing emphases are the special tooth profile designs (such as the sandwich teeth), extremely low face runout requirements, ultra-fine surface treatments to prevent the material edge chipping or delamination, and the evaluation of the anti-static and corrosion resistance properties.

Handheld machine saw blades: The saw blades used for the handheld power tools such as the angle grinders and stone cutters. In addition to the routine testing, the safety properties are the top priority, and the burst safety at the maximum speeds (above 1.6 times the rated speeds), the reliability of the mounting holes and the permanent safety warning markings need to be strictly tested.

Ultra-thin cutting saw blades: The thin saw blades used for the material-saving cutting or grooving of the valuable materials. The testing core is the high elasticity, high fatigue strength, excellent flatness of the matrices, as well as the working stability under the high-frequency vibrations, ensuring their narrow kerf cutting abilities and long lives.

Special tooth profile and combination saw blades: Such as the variable pitch saw blades and combination planing saw blades. The testing needs to verify the acoustic noise reduction effects, vibration damping properties or composite machining abilities of their special tooth profile designs, and the functional verifications need to be carried out through the professional cutting test benches.

Testing Methods

Dimension and geometric tolerance measurement method: The high-precision digital callipers, micrometers and inside diameter dial gauges are used to measure the basic dimensions; the dial indicators and micrometer dials combined with the precision V-blocks or planes are used on the runout testers to measure the radial and face runouts; the platforms, feeler gauges or optical projectors are used to test the flatness. The measurement needs to be carried out in the constant-temperature environments to exclude the thermal expansion effects.

Tooth profile parameter optical projection method: The tool microscopes, projectors or advanced image measuring instruments are adopted to enlarge and project the saw tooth profiles onto the screens, and the parameters such as the rake angles, clearance angles and tooth heights are precisely measured through the standard template comparison or software automatic analysis, with the high efficiency and objective data.

Mechanical property testing method: The Rockwell or Vickers hardness testers are used for the multi-point hardness testing at the specified positions of the matrices and teeth; according to the GB/T 228.1 standard, the tensile testing is carried out on the matrix specimens on the universal material testing machines to obtain the strength and plasticity indicators; the impact testing machines are used for the Charpy impact testing to evaluate the toughness.

Non-destructive flaw detection method: The ultrasonic flaw detection (UT) is adopted for the welded parts to detect the internal defects such as the cracks and lack of fusion; the colour penetrant flaw detection (PT) is adopted to detect the surface open defects. The X-ray flaw detection (RT) can be used to check the diamond distributions inside the segments and the matrix densities.

Dynamic balance testing method: The saw blades are installed on the spindles of the dynamic balancing machines and rotated at the set working speeds or near the speeds. The sensors detect the magnitudes and phases of the unbalance amounts, and the corrections are carried out through the weight removal (drilling) or weight addition (adding the balance weights) until meeting the standard (such as the G2.5 and G6.3 grades) requirements.

Metallographic analysis method: The samples are taken from the non-working areas of the saw blades. After the mounting, grinding, polishing and etching, the micro-structures are observed under the metallographic microscopes or scanning electron microscopes (SEM), and rated according to the relevant standards, thereby inferring and judging the rationality of the heat treatment processes.

Functional cutting testing method: On the standardized cutting test benches, the inspected saw blades are used to actually cut the standard test materials (such as the wood and steel of the specific designations). Through the measurement of the cutting powers, feed forces, cutting temperatures, kerf surface roughness and saw blade wear amounts, their comprehensive properties are comprehensively evaluated.

Testing Standards

Domestic Standards:

1. GB/T 11270.1, Superhard abrasive products — Diamond circular saw blade

2. GB/T 228.1-2021, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

3. GB/T 229-2020, Metallic materials — Charpy pendulum impact test method

4. GB/T 230.1-2018, Metallic materials — Rockwell hardness test — Part 1: Test method

5. GB/T 4340.1-2009, Metallic materials — Vickers hardness test — Part 1: Test method

International Standards:

1. ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

2. ISO 148-1, Metallic materials — Charpy pendulum impact test — Part 1: Test method

3. ISO 1940-1, Mechanical vibration — Balance quality requirements for rotors in a constant (rigid) state — Part 1: Specification and verification of balance tolerances

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

High-precision geometric quantity measuring instruments: Including the digital micrometers (resolution 0.001mm), runout testers (with the high-precision micrometer dials), large tool microscopes or two-dimensional image measuring instruments. These equipment are the fundamental guarantees of obtaining the basic geometric parameters and geometric tolerances of the saw blades, and need to be regularly calibrated to ensure the data accuracy.

Dynamic balancing machine: Divided into the hard bearing and soft bearing types, selected according to the saw blade weights and balance precision requirements. The high-end dynamic balancing machines have the functions such as the automatic measurement, phase positioning, weight removal/addition amount calculation, and can simulate the high-speed rotation states. They are the core equipment of guaranteeing the stable operation of the saw blades.

Material testing machine and hardness tester: The microcomputer-controlled electronic universal testing machines are used for the mechanical property testing such as the tensile and bending; the Rockwell hardness testers (HRC scales) and Vickers hardness testers are respectively suitable for the precise measurement of the overall matrix hardnesses and local tooth tip hardnesses. The equipment needs to meet the calibration specifications such as ISO 7500-1.

Non-destructive testing equipment: The portable or bench-type ultrasonic flaw detectors, equipped with the appropriate probes for the welded interface testing; the colour penetrant flaw detection reagent kits for the surface defect screening; for the diamond saw blades, the industrial CT or micro-focus X-ray equipment may be used for the three-dimensional structure reconstruction analysis of the interiors.

Metallographic preparation and observation system: Including the automatic grinding and polishing machines, mounting machines, metallographic etchants and inverted metallographic microscopes. The advanced laboratories are equipped with the scanning electron microscopes (SEM) and energy dispersive spectrometers (EDS) for the more in-depth micro-area morphology observation and composition analysis.

Cutting performance test bench: Integrating the high-rigidity spindles, high-precision feed systems and multi-channel data acquisition systems (measuring the cutting forces, torques, powers, vibrations and temperatures, etc.). This equipment can simulate the real working conditions, and is the key platform of verifying the saw blade designs, carrying out the product quality benchmarking and research and development.

Surface analysis instruments: The coating thickness gauges (such as the eddy current and magnetic types) are used to measure the thicknesses of the anti-rust or anti-friction coatings; the roughness profilometers are used to evaluate the surface finishes of the matrices and tooth rake faces; the adhesion cross-cut testers are used to qualitatively evaluate the coating bonding strengths.