South Bend Tools
For Machines Mfd. Since 9/20
Model SB1092 & SB1094
-27-
S Y S T E M D E S I G N
Determine Main Line Duct Size
Determine Branch Line Duct Size
400
400
600
850
400
250
100
Dust
Collector
5"
6"
7"
Table Saw
Planer/
Moulder
Miter
Saw
Jointer Sander
Planer
Shaper
400
400
600
850
400
250
100
4"
4"
4"
6"
4"
4"
5"
5"
6"
7"
Table Saw
Miter
Saw
Jointer Sander
Planer
Shaper
Planer/
Moulder
Dust
Collector
Figure 36. Main line size labeled on sketch.
Figure 38. Sizing chart for multiple machines on the
same branch line.
Figure 37. Branch line duct sizes labeled.
The general rule of thumb for a main line duct
is that the velocity of the airflow must not fall
below 3500 FPM.
For small/medium sized shops, using the inlet
size of the dust collector as the main line duct
size will usually keep the air velocity above 3500
FPM and, depending on your system, will allow
you to keep multiple branches open at one time.
Mark your drawing, as shown in the figure
below, but using the inlet size for your dust
collector as the main line.
The general rule of thumb for a branch line duct
is that the velocity of the airflow must not fall
below 4000 FPM.
For small/medium sized shops, using the dust
port size from the machine as the branch line
duct size will achieve the correct velocity in most
applications. However, if the dust port on the
machine is smaller than 4", make the branch line
4" and neck the line down right before the dust
port.
Note:
Systems with powerful dust collectors work
better if multiple blast gates are left open. This
also allows you to run two machines at once.
Experiment with different combinations of blast
gates open/closed to find the best results for your
system.
Write your determined branch line sizes on your
drawing, as shown in the following figure.
If two machines will connect to the same branch
line and both will operate at the same time, then
add the required CFM for each machine together
and find the closest total CFM in the table below
to determine the correct branch size.
If both machines will never run at the same time,
reference the machine with the biggest dust port
in the table below and add blast gates after the
Y-branch to open/close the line to each machine.
Total CFM
Branch Line Size
400
4"
500
4"
600
5"
700
5"
800
6"
900
6"
1000
6"
