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    Scalloped / Polygonal Blades

    24.08.2020 TKM

    Scalloped / Polygonal Blades

    The cause for scalloped blades is an irregular grinding process over the circumference of the blade. The irregular grinding process can be caused by:

    • Too high and/or unbalanced grinding pressure of the front and back stones (1)
    • Too high dynamic run-out of the mounted blade (2)
    • Too high axial static run-out of the mounted blade (2)
    • Dirty or glazed grinding wheels (3)
    • Constant blade speed (4)
    • Too long grinding time (5)


    • Too high grinding pressure (1)
    The grinding wheels remove too much material on initial impact (static grinding wheels contact spinning blade)
    Blade deflection caused when the grinding wheels make initial contact with the blade is reverted after the wheels retract => high degree of blade vibration
    On request, we execute an individual grinding seminar on-site.

    • Too high dynamic run-out of the mounted blade (2)
    The static lateral run-out of the log saw blade influences the dynamic run-out (vibrations) and therefore the static lateral run-out should be as low as possible. The maximum lateral run-out of new TKM Group blades outperforms the OEM requests. The value is laser etched on each TKM Group log saw blade. High vibrations on the mounted blade may be the influence of the bearing(s) at the arbor and/or of the surface of the flange. The total end play of the flange should not exceed 0,03 mm.

    • Too high axial static run-out of the mounted blade (2)
    The dynamic lateral run-out is influenced by the static lateral run-out (see slide 8) but also from the type of machine respectively the RPM of the blade. Each Log Saw machine creates at certain RPMs of the blade more dynamic lateral run-out (vibrations). If the static run-out of the log saw blade is within tolerance the dynamic vibrations can be reduced. The best solution for breaking up the vibration pattern (and therefore the grinding pattern) is to change the RPM of the blade steadily. Most modern machines have the ability to vary circumferential speed of the blade automatically between adjusted values (for example between 40 – 45 m/sec.)
    TKM Group is the only company which checks the dynamic run-out with an internal standard on every blade.

    • Dirty or glazed grinding wheels (3)
    The grinding wheels collect grinding dust, glue and metal particles during the grinding process. Additionally, oil-based lubricant combined with the grinding dust, glue and other particles gum up the grinding wheels. This buildup inhibits the regular grinding process. If it is not possible to reduce the amount of grinding dust and glue present on the log saw blade the grinding wheels should be cleaned regularly, in worst case several times per shift. To reduce glue and oil on the blade we recommend an adequate lubrication system.

    • Constant blade speed (4)
    Constant blade speed results in a constant vibration pattern. The initial grinding wheel contact happens in the same locations => The wheels remove too much material in the same locations which results into a scalloped blade
    We recommend a variable speed drive. If it is not possible to install a variable speed drive the operator may be able to periodically change the bade speed manually +/- 2%.

    • Too long grinding time (5)
    Excessive grind time has been observed to caused log saw blade scalloping on several occasion. Grinding durations should never exceed 4 seconds.

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