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DUST COLLECTION FOR THE
SMALL SHOP
It
seems that are more articles written about dust collection
than those that discuss “how to build a router table”. We
installed a system about 3 years ago and it has proven to be
the very best investment that we have made. One of the
amazing things that happened is that it reduced the amount
of colds that we get every year and our general health seems
to be better. We work in our shop every day and for the
weekend user you may not notice this type of change. The
most important thing is, the shop is cleaner, not dusty and
I am sure that we must be healthier with the system.
There are five things that
you need to consider before planning the size of your
system. How much to spend, type of collector, piping,
location of the machines and sound levels.
Today there are many manufactures of systems and we will
provide a list of them at the end of this article. Before
we start let me discuss the advantages of plastic pipe verse
steel. Drain and ABS plastic pipe is inexpensive, easy to
work with and many people use it. One thing that happens is
that static electricity builds up and can suddenly discharge
and spark a fire or even worst an explosion. Losing your
shop or your home to a fire because plastic pipe, is too
high a price to pay for saving time and a couple of bucks on
the system.
Static electricity occurs in
steel pipe, but the difference is that grounded steel pipe
discharges the electrical charge. Galvanized sheet metal
piping is strong and light an only takes a pair of tin
snips, a pop riveter and a crimping tool to install an
entire system. You will find that 24-ga.or 26-ga. HVAC pipe
is available at most home supply centers.
The following are suggestions on
sizing the branch ducting for your machines. (CFM cubic feet
per minute)
10” Table saw
10” Radial Arm Saw
12” Thickness planner
Bandsaw
Jointer 8’ wide
Disk sander Combo 6 x 48 with 10” disc
Spindle Shaper 1 ˝ HP
3 HP
Wood lathe
* Lathes will vary based on the material and
the size. |
350-500 cfm
350 cfm
500 cfm
450 cfm
350-400 cfm
600 cfm
550 cfm
700 cfm
550 cfm
*Drill presses, scroll saws and other light duty
machines will range in the 350-400 cfm requirements |
4 in 5 in.
4 in
5 in
4 in
4 in
4 in
5 in
6 in
5 in |
We have found that the three
highest producing machines, are the planner, shaper and the
table saw. The planner and shaper for the bulk and the
heavy chips and the table saw for the continuous amount of
material produced. If you put these machines at the end of
the system you may find that the large chips from the
planner will build up in the pipe. Source the largest
producers as close to the beginning of the system as
possible.
Our system is 2 hp and has an
estimated cfm of 1450. Our main line from the collector is
6” stepped to 5” for the line runs and 4” to the machines.
Each machine has a separate blast gate and there are no hard
90-degree turns in the system. We used the large radius
elbows and it really helps the material negotiate the
turns. When we merged the ducts we used 45-degree wye
connectors whenever we could.
The continuous noise level that
the collector generates can be annoying after a long day in
the shop. If you surround the collector with a rolling 2x4
panel with drywall and some insulation it will reduce the
level quite a bit. We have wired the collector to turn on
with a hand held remote that works very well.
Sandor Nagyszalanczy has written
one of the very best books on dust collection and if you are
considering adding a system you should spend the time
reviewing it. We carry the revised edition AFD325 and it
retails for $18.95
HOW TO DESIGN THE
SYSTEM
Shop Layout
You need to consider the
limitations of your workspace. Most shops today are 2 or
more garage areas. As discussed earlier, place the machines
requiring the largest cfm of airflow closest to the
collector. Our suggested cfm chart will help in locating
your machines.
Shop Drawing
Using grid paper, make a scale
drawing of your shop and the exact location and diameter of
each dust port.
Determine the CFM
requirement for your shop
Add up all the cfm requirements
for all the machines dust needs. The cfm for the entire
shop may exceed the capacity for the dust collector. It
that is the case, blast gates will allow machines not in use
to be isolated from the dust system by closing off those
machines. There are some blast gate manufactures that have
systems that sense the electrical use of the machine when it
is turned on to automatically open the blast gate.
Locate the position of the
main duct line.
Be sure to run the ducting so
that it ends directly above each dust port.
Determine the necessary duct
size.
On your drawing begin at the machine farthest away from the
collector and work back towards it. Determine the
appropriate diameter of the pipe from the CFM needs at the
first machine. Continue on to the next machine. Size your
branch from the chart above for pipe size. Continue on to
the remaining machines, adding blast gates as necessary
until the main line is equivalent to the size of the
collector inlet.
Turn on the system and check for
leaks as there will be many. GE silicon sealant works very
good and in some areas you may wish to use duct tape as it
may be necessary to remove a section of pipe when a large
piece gets stuck. The main culprit for this is the table
saw, as very small narrow cut offs about 6” long end up in
the system and can get caught side ways in the pipe.
Enjoy the good health, clean
shop and all the other benefits you will find after you have
installed your new system.
Brian Murphy
American Furniture Design Co
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