Gilson ASTM D4791 Operating Manual

Four-Station Proportional Caliper

HM-38B

ASTM D4791

INTRODUCTION:

These instructions are a general guide for operation of this
device. The complete procedure for determination of relative
shape characteristics of coarse aggregates using the Four­Station Caliper is described in ASTM D4791. The user should
carefully review the ASTM procedure before testing.

OPERATING INSTRUCTIONS:

Individual particles of aggregate of specific sieve sizes are
measured to determine the ratios of width to thickness and
length to width. The applied ratios are 1:2, 1:3, 1:4, and 1:5
according to desired specifications.

OPERATING MANUAL

HM-38B

A. Test for Flatness B. Test for Elongation

A. For Classification of Flat Particle Testing:

The user should set the larger opening of the Caliper
equal to the particle width. If the thickness of the same
particle can be placed within the smaller opening without
readjusting the Caliper, the particle is classified as Flat.

B. For Classification of Elongated Particle Testing:

The user should set the larger opening of the Caliper equal
to the particle length. If the width of the same particle can
be placed within the smaller opening without readjusting
the Caliper, the particle is classified as Elongated.

If the particle does not meet either classification of Flat or
Elongated, it is classified as Neither Flat nor Elongated.

(Continued on back.)

Rev: 06/15/2015

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DEFINITIONS:

MAINTENANCE:

Flat Particles — The particles having a ratio of width to thick­ness greater than a specified value.

Elongated Particles — The particles having a ratio of length
to width greater than a specific value.

Very little maintenance is required for the Four-Station Caliper.
Clean the Caliper before each test to avoid foreign particles
which may effect results. Every six months add a drop of oil
into the ratio holes for smooth operation. Periodically, inspect
parts for wear to ensure compliance with ASTM D4791.