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Old January 23rd 06, 03:07 AM posted to rec.woodworking
mywebaccts (at) PLUGcomcast.net
 
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Default 4" vs 6" ducting for effective dust collecting

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?

Jack


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Old January 23rd 06, 03:23 AM posted to rec.woodworking
Joseph Connors
 
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Default 4" vs 6" ducting for effective dust collecting

I converted from 4" to 6" after reading Bill's site. The flow is much
better, though I will need to convert to a cyclone in the near future.

To me, cost is irrelevant. We spend $1000's of dollars on our tools to
make this dust, that if we don't collect right at the source as soon as
it is generated, will end up in our lungs causing us untold health
problems. I say, spend a $1000 or so, forgo the upgrade on that tablesaw
or jointer, and ensure that we can continue woodworking for years to
come. Anything else seems like false economy to me!



mywebaccts (at) PLUGcomcast.net 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?

Jack


--
Joseph Connors
The New Golden Rule:
Those with the gold, make the rules!
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Old January 23rd 06, 03:39 AM posted to rec.woodworking
Edwin Pawlowski
 
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Default 4" vs 6" ducting for effective dust collecting


"mywebaccts (at) PLUGcomcast.net" "mywebaccts (at) PLUGcomcast.net" wrote
in message

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


I don't think it is inadequate, but 6" is definitely better. The longer the
runs, the difference becomes more pronounced.


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Old January 23rd 06, 03:47 AM posted to rec.woodworking
DonkeyHody
 
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Default 4" vs 6" ducting for effective dust collecting

I've spent a lot of time at Bill's Place too. The only question in my
mind is whether the nexus between occasional exposure to wood dust and
lung problems has been adequately established by the medical community.
I'm not arguing against it, I'm just not yet fully convinced.

I haven't done any controlled experiments like he did, but as an
engineer, I find no fault with his statements about what is necessary
to capture that fine dust that causes so much concern. I totally agree
that it's easy enough to collect the chips that you'd be sweeping off
the floor, but it requires much more air flow AT THE TOOL to capture
all the micro-particles. To move that much air, you need big blowers
and big pipes.

DonkeyHody
"Every man is my superior in that I can learn from him." - Thomas
Carlyle

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Old January 23rd 06, 04:32 AM posted to rec.woodworking
Phisherman
 
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Default 4" vs 6" ducting for effective dust collecting

On Sun, 22 Jan 2006 20:07:12 -0700, "mywebaccts (at) PLUGcomcast.net"
"mywebaccts (at) PLUGcomcast.net" 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?

Jack



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.


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Old January 23rd 06, 05:30 AM posted to rec.woodworking
leonard
 
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Default 4" vs 6" ducting for effective dust collecting

You can always use 5in pipe too, cost less than 6 and more then 4 but gives
more flow than 4



Len
"


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Old January 23rd 06, 06:35 AM posted to rec.woodworking
mywebaccts (at) PLUGcomcast.net
 
Posts: n/a
Default 4" vs 6" ducting for effective dust collecting

Good point. I'm not sure that 5" piping and connectors are easy to come
by in my are (Los Alamos, NM). All I've seen is the 4" and the 6". But
I'll check in Santa Fe. That might be a nice compromise.

Jack

leonard wrote:
You can always use 5in pipe too, cost less than 6 and more then 4 but gives
more flow than 4



Len
"



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Old January 23rd 06, 06:37 AM posted to rec.woodworking
mywebaccts (at) PLUGcomcast.net
 
Posts: n/a
Default 4" vs 6" ducting for effective dust collecting

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 heard).

Jack

Phisherman wrote:

On Sun, 22 Jan 2006 20:07:12 -0700, "mywebaccts (at) PLUGcomcast.net"
"mywebaccts (at) PLUGcomcast.net" 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?

Jack




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.


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Old January 23rd 06, 07:01 AM posted to rec.woodworking
Joseph Connors
 
Posts: n/a
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) PLUGcomcast.net 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
heard).

Jack

Phisherman wrote:

On Sun, 22 Jan 2006 20:07:12 -0700, "mywebaccts (at) PLUGcomcast.net"
"mywebaccts (at) PLUGcomcast.net" 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?

Jack





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!
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Old January 23rd 06, 01:30 PM posted to rec.woodworking
Art Greenberg
 
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Default 4" vs 6" ducting for effective dust collecting

On Sun, 22 Jan 2006 20:07:12 -0700, mywebaccts (at) PLUGcomcast.net 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?


It depends. The article on Bill's site tries to explain why and when to choose
a particular size. You can't ignore the physics behind what's going on without
reducing efficiency.

Look at the velocity needed to keep the dust suspended in the airstream. If
you don't have that velocity, the dust will settle out in the pipe. Velocity
is a function of CFM and pipe cross-section. FOr a given CFM, making the pipe
larger (larger cross section) will result in lower velocity. At some point,
you end up with a situation where the dust never makes it to the blower.

In vertical runs, gravity is working to reduce velocity as well. So you might
need a smaller pipe in vertical runs to keep the dust moving.

Too small a pipe, on the other hand, introduces a lot of frictional loss, so
the velocity will drop. The result is the same; the dust does not move through
the system.

For a small shop, it is probably not necessary to go through a bunch of
precise computations. Rule of thumb ar a good thing. I used one in designing
my DC system, and its worked very well for me. I think I found this on Bill's
site, but I don't remember so well, and I'm not looking at that right now. But
it said that, for a 2HP/1200CFM blower, 6 inch pipe is about right for
horizontal runs, but a bit too big for vertical runs. So I used 6 inch pipe
everywhere, except for the drops to my machines, where I used 4 inch pipe. I
built my system using S&D PVC, and used 45 degree bends exclusively (2 in a
row where I needed a 90 degree bend) and 45 degree Ys for take-offs.

--
Art



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