1
24-080
Secrets of the Bond Ball Mill Grindability Test
Alex Doll
Alex G Doll Consulting Ltd, Ireland
Vladimir Nikolić
University of Belgrade,
Department for Mineral and Recycling Technologies,
Bor, Serbia
ABSTRACT
The Bond ball mill grindability test is one of the most com-
mon metrics used in the mining industry for ore hardness
measurements. The test is an important part of the Bond
work index methodology for designing and measuring the
efficiency of mineral grinding circuits.
In spite of being called “Bond’s Law,” the work index
equations are not a law of nature but rather an empiri-
cally measured regression of a large data set collected by the
Allis- Chalmers corporation in the period between 1930
and 1952. As a regression, it is valid within a specific “cali-
bration space,” and great care is required when deviating
the test procedures or observing results that are outside of
that calibration space.
This paper is a collected summary of other works by
the Authors that describe feed sizes, product sizes, quality
control checks, and other information about interpreting
the test and using its results. Examples of adjustments that
are sometimes required when using the test are: changing
the test product (P80), and coping with a feed that is too
fine to apply the “proper” feed preparation steps (such as is
sometimes observed from HPGR or SAGDesign product
testing). Related metrics, like the Morrell Mib value and
Levin B value will be discussed, along with recommenda-
tions for their use on design projects.
The intended audience is any user of laboratory work
index test data.
INTRODUCTION
The ball mill grindability test sometimes referred to as
“the Bond test” was developed in the 1930s by the Allis
Chalmers company to help them perform ore hardness
characterisation testing to assist in industrial mill sizing
Maxson et al, (1933). It was extended by Bond (1952) to
provide a ‘work index’ result that was empirically calibrated
to make a laboratory work index match the corresponding
work index measured in an industrial grinding mill. The
fitted equation, in metric form, is given as Equation (1).
Wi
P G
P F
1.1203 44.5
10 10 .
100
0 23 0.82
80 80
$
#=
-c m
(1)
where:
Wi =work index (treat as unitless, metric basis)
P100 =closing screen size (µm)
G =net mass (grams) of undersize product per unit
revolution of the mill, (g/rev)
P80 =the 80% passing product particle size (µm)
F80 =the 80% passing feed particle size (µm)
24-080
Secrets of the Bond Ball Mill Grindability Test
Alex Doll
Alex G Doll Consulting Ltd, Ireland
Vladimir Nikolić
University of Belgrade,
Department for Mineral and Recycling Technologies,
Bor, Serbia
ABSTRACT
The Bond ball mill grindability test is one of the most com-
mon metrics used in the mining industry for ore hardness
measurements. The test is an important part of the Bond
work index methodology for designing and measuring the
efficiency of mineral grinding circuits.
In spite of being called “Bond’s Law,” the work index
equations are not a law of nature but rather an empiri-
cally measured regression of a large data set collected by the
Allis- Chalmers corporation in the period between 1930
and 1952. As a regression, it is valid within a specific “cali-
bration space,” and great care is required when deviating
the test procedures or observing results that are outside of
that calibration space.
This paper is a collected summary of other works by
the Authors that describe feed sizes, product sizes, quality
control checks, and other information about interpreting
the test and using its results. Examples of adjustments that
are sometimes required when using the test are: changing
the test product (P80), and coping with a feed that is too
fine to apply the “proper” feed preparation steps (such as is
sometimes observed from HPGR or SAGDesign product
testing). Related metrics, like the Morrell Mib value and
Levin B value will be discussed, along with recommenda-
tions for their use on design projects.
The intended audience is any user of laboratory work
index test data.
INTRODUCTION
The ball mill grindability test sometimes referred to as
“the Bond test” was developed in the 1930s by the Allis
Chalmers company to help them perform ore hardness
characterisation testing to assist in industrial mill sizing
Maxson et al, (1933). It was extended by Bond (1952) to
provide a ‘work index’ result that was empirically calibrated
to make a laboratory work index match the corresponding
work index measured in an industrial grinding mill. The
fitted equation, in metric form, is given as Equation (1).
Wi
P G
P F
1.1203 44.5
10 10 .
100
0 23 0.82
80 80
$
#=
-c m
(1)
where:
Wi =work index (treat as unitless, metric basis)
P100 =closing screen size (µm)
G =net mass (grams) of undersize product per unit
revolution of the mill, (g/rev)
P80 =the 80% passing product particle size (µm)
F80 =the 80% passing feed particle size (µm)