4" vs 6" ducting for effective dust collecting

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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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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!
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On Sun, 22 Jan 2006 19:23:38 -0800, Joseph Connors

honestly what did woodworkers like my father loose by spending years in their shops without any DC's....? My Dad passed away in 2002 at the age of 87.
I have had my DC system for at least 10 years most likely more BUT to be truthful I never installed it for health reasons... NOPE..*I just happen to like relaxing and working in a clean shop.. I retired almost 8 years ago and have spent at least 3-4 hours in the shop every day since ... a lot less then that when I was working naturally...
I'm sorry...but spending 1000's of dollars on DC systems for health reasons to me is not really worth the effort BUT spending that same amoput of money to increase your enjoyment of life (like a clean shop) PLUS a more healthful envioroment IS WORTH IT
Will I change over to 6 in runs...??? Ya know I most likely will BUT only because it would be an interesting project...
Bob G.
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Bob:
As far as your father is concerned, a number of factors are in play here. Perhaps he did not a predisposition to an allergy or lung problem. Lung problems run in my family. Another point is in the past there was a lot less sanding done, especially by machine. They tended to plane and scrape much more so the shop environment was healthier.
As far spending the money goes, everyone makes that decision for themselves as to their priorities in life. Its a personal choice to gamble that it won't happen to you.
Another factor, Bob, is the shop itself. If your shop is open to the air, then air quality is less of a concern. These bags collectors with small 4" pipe are dust pumps, pure and simple. When you watch them inflate with sunlight in back of them, you can see the cloud of dust produced.
As far as I'm concerned, you need a large blower with 6" pipe and very good (<.5 micron - certified) filtration.
Bob G. wrote:

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The size of the pipe is _completely_ orthogonal to the efficacy of the collector bags. A given collector bag will produce the same "cloud of dust" irrespective of the size of the ductwork.
So long as the chips and dust are being transported from the machine to the collector, the size of pipe is far less important than the quality and weave of the bag.
Typical garage shop, 4" is fine.
scott
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Scott Lurndal wrote:

I agree completely.

You hit the nail on the head! "So long as the chips and dust are being transported from the machine to the collector" .... thats the whole thing ... 4" pipe, in most applications, cannot carry enough volume of air to transport the FINEST dust from the machine to the collector.
The vast majority of bags don't begin to achieve the necessary filtration level.

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Scott Lurndal wrote:

Wow! <G>
Barry
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"mywebaccts (at) PLUGcomcast.net" <"mywebaccts (at) PLUGcomcast.net"> wrote in message

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

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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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
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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.
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And some people have allergic reactions to peanuts and can no longer eat peanut butter. The vast majority of people who have and do work with wood don't have allergic reactions. Don't blow the problem all out of proportion.

And whether or not you use dust collection won't prevent it, unless you have _perfect_ dust collection, which is probably unachievable (no hand sanding, let someone else empty the collector, vacuum the shop floor ten times daily, etc.).

In an industrial setting, perhaps. For a home shop?
scott
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Scott Lurndal wrote:

That is true as far domestic woods are concerned ... not true at all for exotics. Allergic reactions can develop over time ... the more exposure, the sooner it can happen. Also, wood dust is a know carcinogen.
But you are right in that most of the time allergic reactions are not going to be the problem. Lung problems are the main issue and that takes time and exposure.

collection, which I agree is probably unachievable in a practical sense, just reducing the exposure will suffice. I'm not saying that one whiff of wood dust and it off to the pulmonary care unit ... we're talking reasonable precautions here.

pipe/blower/filtration combination is what matters.
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Joseph Connors wrote:

You may wish to also consider the *amount* of exposure. Most hobbyists do not spend 7-8hrs a day in the shop. Many professionals could.
In a case like this, the hobbyist may realistically decide that a 4" system is better than nothing, but that the 6" system isn't worth the upgrade.
Personally, I do software for a living. I am *far* more picky about the quality of my monitor/chair/desk than most people, because I spend so much time there.
On the other hand, my current dust collection strategy is a shopvac and a face mask because I might spend an hour a week actually making dust.
Chris
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Chris:
I hear what you're saying. I understand though from Bill's site that some studies have indicated that the typical hobbiest woodworker has more exposure than large industrial settings because the size of the particles involved are smaller in a hobby situation than in an industrial one. With the large industrial settings the bag house is located outside and therefore no threat to air quality at all, whereas in a small shop the air is recirculated.
Chris Friesen wrote:

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Sure - it you eat enough of it.

It's not a matter of physical location, it's a matter of volume. Home shops don't generate the volume of "carcinogens" that production shops do.
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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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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
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"mywebaccts (at) PLUGcomcast.net" <"mywebaccts (at) PLUGcomcast.net"> wrote in message

while I haven't specifically looked for pipe for my DC yet, I tend to see only 4" and 6". I'm sure 5" is available from the plumbing supply houses but it probably costs a bit more. I should have said I'm looking at the PVC S&D piping. I'm in the process of designing a new shop to build when I get some time and money and plan to do 6" under the floor with a cyclone (Bill's Airfoil design) but right now I'm working in my garage where I have no room for a cyclone or piping. I'll keep an eye out here in town to see if 5" is more prevalent than I remember and let ya know. I head up to Angel Fire on a fairly regular basis and we could arrange to meet somewhere if you wanted me to pick it up. Cheers, cc
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