8
particles means that the all-wearing bit is not cutting but
crushing and fracturing the coal randomly. Observations
of particle size distribution at all sizes reveal a more erratic
cutting and more energy- demanding breaking process, as
is characteristic of well- cleaned cutting instruments.
Bit Penetration
0.2-inch penetration: The shallowest penetration yields
the lowest total particle count and a concentrated distribu-
tion. The most significant number of particles lies in the
200–300mm range (22 particles), but significant amounts
were also found in the 300–400mm range (17 particles).
There are noticeably fewer particles in both the small and
large size bands. This means shallow penetration allows for
smoother cutting with less material breakage, possibly due
to lower force and more controlled cutting.
0.4-inch penetration: The particle distribution fol-
lows the same trend at this intermediate penetration depth,
albeit with fewer aggregate counts. The maximum is still
in the 100–200 mm range (40 particles), but a significant
number are in the 200–300mm range (34 particles). The
pattern decreases much more for larger particles than for
deeper penetration. The cumulative percentage increases
up until 300mm and dips down after that, indicating that
most of the cutting occurs with medium-sized particles.
0.5-inch penetration: The deepest penetration has
the largest overall number of particles and the broadest
range of sizes. Most particles (53) occur within the range
of 100–200mm, and the number is slowly declining for
bigger sizes. The cumulative distribution curve shows that
about 80% of particles are less than 400mm. That implies
that deeper penetration yields more fragments in aggregate
and tends to yield a more significant proportion of smaller
particles, probably due to the higher material interaction
and force levels at deeper cuts.
Larger Fines Analysis
The fines generation analysis has strong correlations with
the penetration depth and bit wear. These results indi-
cate an inverse correlation between penetration depth and
0 5
22
17 6 4 4 3 0 0 2
0
20
40
60
80
100
120
Particle size (mm)
cumulative cumulative %
0 5
22
17
6 4 4 3 0 0 2
Particle size (mm)
Figure 12. Particle size distribution of 0.2-inch penetration
4
40
34 6
13 4 2 1 2 1 1
0
20
40
60
80
100
120
Particle size (mm)
cumulative cumulative %
4
40
34
6
13
4 2 1 2 1 1
Particle size (mm)
Figure 13. Particle size distribution of 0.4-inch penetration
Cumulative
%
Particle
number
%evitalumuC
rebmunelcitraP
particles means that the all-wearing bit is not cutting but
crushing and fracturing the coal randomly. Observations
of particle size distribution at all sizes reveal a more erratic
cutting and more energy- demanding breaking process, as
is characteristic of well- cleaned cutting instruments.
Bit Penetration
0.2-inch penetration: The shallowest penetration yields
the lowest total particle count and a concentrated distribu-
tion. The most significant number of particles lies in the
200–300mm range (22 particles), but significant amounts
were also found in the 300–400mm range (17 particles).
There are noticeably fewer particles in both the small and
large size bands. This means shallow penetration allows for
smoother cutting with less material breakage, possibly due
to lower force and more controlled cutting.
0.4-inch penetration: The particle distribution fol-
lows the same trend at this intermediate penetration depth,
albeit with fewer aggregate counts. The maximum is still
in the 100–200 mm range (40 particles), but a significant
number are in the 200–300mm range (34 particles). The
pattern decreases much more for larger particles than for
deeper penetration. The cumulative percentage increases
up until 300mm and dips down after that, indicating that
most of the cutting occurs with medium-sized particles.
0.5-inch penetration: The deepest penetration has
the largest overall number of particles and the broadest
range of sizes. Most particles (53) occur within the range
of 100–200mm, and the number is slowly declining for
bigger sizes. The cumulative distribution curve shows that
about 80% of particles are less than 400mm. That implies
that deeper penetration yields more fragments in aggregate
and tends to yield a more significant proportion of smaller
particles, probably due to the higher material interaction
and force levels at deeper cuts.
Larger Fines Analysis
The fines generation analysis has strong correlations with
the penetration depth and bit wear. These results indi-
cate an inverse correlation between penetration depth and
0 5
22
17 6 4 4 3 0 0 2
0
20
40
60
80
100
120
Particle size (mm)
cumulative cumulative %
0 5
22
17
6 4 4 3 0 0 2
Particle size (mm)
Figure 12. Particle size distribution of 0.2-inch penetration
4
40
34 6
13 4 2 1 2 1 1
0
20
40
60
80
100
120
Particle size (mm)
cumulative cumulative %
4
40
34
6
13
4 2 1 2 1 1
Particle size (mm)
Figure 13. Particle size distribution of 0.4-inch penetration
Cumulative
%
Particle
number
%evitalumuC
rebmunelcitraP