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Joseph Connors
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Default 4" vs 6" ducting for effective dust collecting

Some people have had allergic reactions to wood dust and no longer can
work wood. These reactions can come about after prolonged exposure, with
no obvious ill effects to breathing the dust, and all of a sudden they
either must wear a respirator or not work wood. If you have this genetic
trigger, it can happen right out of the blue with little or no warning.

4" pipe CAN work for some machines with a large enough blower. It
depends on a lot of factors. Its just for most machines and blowers, the
6" pipe is required.

mywebaccts (at) wrote:
My workshop seems painfully small to accomodate a 6" ducting system. I
expect most of my work to be routing and scroll sawing and hence don't
think the dust problem will justify the expense of a 6" system.

Of course, it's dangerous to put a price on one's health. Lung problems
caused by inhalation of microfine particles is pretty nasty (so I've


Phisherman wrote:

On Sun, 22 Jan 2006 20:07:12 -0700, "mywebaccts (at)"
"mywebaccts (at)" wrote:

I'm reading "Bill's Place" (Bill Pentz) and his writeups on what does
or doesn't constitute an effective dust collection system. He insists
that 4" ducting is woefully inadequate for safe dust collection. He
writes that 6" is what is needed.

His writeup gets fairly technical and sounds very convincing. But of
course, using 6" ducting greatly increases the cost of the ducting
for my workshop.

Are there other opinions on this or do people pretty much agree that
4" ducting is inadequate?


I agree that six inch piping is much better than 4, although a bit
less practical for a typical (home) workshop. Pi R squared shows 12
vs 27, meaning that the 6" pipe can move over twice the volume as the
4" pipe in any given time. Now whether the 4" piping is inadequate or
not depends on how quickly sawdust will be produced.

Joseph Connors
The New Golden Rule:
Those with the gold, make the rules!