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Four-Station Proportional Caliper

    Four-Station Proportional Caliper


    Shape characteristics of coarse aggregates are important when determining the performance of materials or mixes. Proportional Calipers are timesaving devices used for the rapid determination of percentages of flat and elongated particles in coarse aggregate fractions of 3/8in (9.5mm) or larger. Units are constructed of durable plated steel, precision-tooled for accuracy.

    For shape determination of flat particle sizing, set the width of a particle in the larger end of the Caliper, then tighten the pivot screw. Without adjusting the Caliper, check the same particle in the smaller measuring end of the Caliper. If the particle fits within the smaller gap, it is considered flat. Elongated particle determination follows the same steps. If the particle is larger than the small measurement in both situations then the particle is considered neither flat nor elongated.

    HM-38B Four-Station Caliper is similar, but provides openings for all four ratios simultaneously, without the need to reposition the pivot screw. Manual testing can be performed more efficiently. Moveable posts are also replaceable.


    • A time-saving way to determine percentages of flat or elongated particles in coarse aggregate
    • Meet requirements of ASTM D4791
    • Optimal for fractions of 3/8in (9.5mm) or larger
    • The sturdy aluminum body is precision-tooled for accuracy

    Product Dimensions

    HM-38B: 16 x 8 x 3in (406 x 203 x 76mm), WxDxH

    Estimated Shipping Weight

    HM-38B: 10.0lb (4.54kg)