Page 90 - Australian Wood Review №103 2019
P. 90
WORKSHOPS
5. Most blade guards allow for no more than 50mm ports.
The upgrade here to 100mm is remarkably effective.
6. Modification of a big boy sander. The port is 150mm
and the additional removable guarding allows for full
dust collection when using the radius.
7. With the guarding removed, sanding the full length
is possible. Note the upgraded port to the right.
6
5 7
There is a wealth of research to support these requirements. of these systems traditionally move exhaust air through
Because we’re aspiring to collect fine dust with these systems some form of filter. As such, the performance of the system
(not wood chips), the volume of air we need to move through is entirely dependent on keeping the filters clean. If you’re
an extraction system becomes significant. Whilst 350cfm like me, this rarely happens at the required frequency.
may be adequate for wood chips, 1000cfm or more will be
required to collect fine wood dust (source billpentz.com). For decades the majority of large workshops have used
cyclone extraction systems for good reason. The inherent
There are two reasons for this. First of all, we need to cyclone design ensures that separation of the majority of
understand that fine wood dust behaves like an aerosol. wood dust occurs prior to the impellor so that the exhaust
Unlike wood chips it becomes airborne immediately. air contains only the finest dust particles.
Secondly, to collect these airborne particles at the source
requires significant volumes of air to be drawn into your A single stage system in comparison has all the extracted
ductwork. Think of it as trying to create a bubble of low dust passing through the impellor with subsequent impact
pressure air around the tool generating the dust. The science on performance. Cyclone systems lose out on cost and
confirms this as something that’s difficult to achieve. If noise, however, I chose a cyclone for my installation due to
you’ve used a garden blower you’ll understand the challenge. their performance advantage and smaller physical footprint.
When used as a blower, they’re effective at blowing dust all
over the place, however, switch them to suction mode and The choice of ducting opens up a host of options in
you’ll find that you need the inlet right on top of the material either rigid or flexible and metal or PVC. My choice was
you’re trying to vacuum. Why is this? Because blowing has PVC, purely for the convenience and flexibility, however,
the benefit of efficiently forcing air flow in one direction. there are some very professional metal ducting solutions
available. Materials aside, the first consideration should be
This advantage is lost in a vacuum system as air is drawn in minimising lengths of ducting and maximising duct size.
from all directions at once. Once again, collecting fine dust
at the source requires large volumes of air to be drawn into Flexible duct should obviously be avoided wherever
your ducting, which requires significant motor power, large possible given the significant resistance to airflow.
impellors and large ductwork. Recognising the research of Bill Pentz, most owners of
standard 2hp extractors nominally rated for greater than
Choosing a style of extractor is largely a decision between 1000cfm of flow may be horrified to recognise that this
a cyclone (photo 3) or the more conventional single stage will be reduced to something closer to 350cfm purely
extractors with bags or pleated filters. Remember that both through the choice of 100mm ducting.
90 Australian Wood Review
