Dust collection pipe diameters?

[Jim Dunn]

I am about to make some recommedations to my friend about the design and layout of the piping for his dust collector. Now the stumbling point His position is that a 1200cfm dust collector is more than twice the cfm necessary to handle the dust from a Grizz 1023 saw, a X5 Unisaw would perform about the same. He intends to run 20-30' of 4" flex hose to his cabinet saw and branch off to his 8" jointer. He's only talking about using 1 blast gate as the jointer "can't use as many cfm's as the cabinet saw" and that leaves about 550cfm to handle the jointer even with the cabinet saw connected.

I think he is missreading the Grizz information and relying on it to design the piping. Try as I might to change his mind I am having no luck. I think he is making a grave mistake. To further compound his misinformation he is used to using Craftm-ans wet dry vacs up to this point. While they make work effectively up to a point they are not dedicated dust collection sytems. Nor do they move the same cfm' as a dust collector.

I am suggesting that he use 6" metal pipe and fittings to a terminating point at the cieling. Then making his drops, with independent blast gates, in 4" flex or metal pipe.

Any information you have on the subject would be helpful as I am going to probably blamed for not enforcing my suggestions if they are found to be true. It will end up being my fault if his original system fails. Go figure

[Bill Turpin]

Running the entire length with flex pipe that is corrugated will have a SERIOUS pressure drop. The system should be run with smooth walled pipe as far as possible. Then use flex for the last few feet.

Bill in WNC mountains

[Steven Wilson]

Your friend's 1200cfm DC unit only has that number if you remove the bags (or canister) and have no pipe attached. Ones the bags are on he'll be lucky to have 600cfm - before any pipe. 4" pipe of any type presents too much surface area as resistance to flow, SP increases fairly rapidly with 4" pipe (even smooth) and besides he has enough power to keep the velocity up. I would probably go with a 6" PVC or metal main and then branch to 5" (if you're using metal) or 6" PVC down to the blast gate. After that 5" or 6" flex to the machine and then reduce to 4" at the tool. BTW his DC doesn't have enough umph to effectively evacuate more than 30' of pipe (including flex).

[Allan Johanson]

Hi Jim,

Listen to the guys above.

Also, give these airflow numbers to your friend. These are when I tested the airflow in my cyclone testing the effects of different ducts. I used proper test equipment so these are real numbers, not some guess.

7.5' of 8" duct.....1700 cfm

...or...

About 10' of 7" duct, a couple 45 deg elbows, and a couple feet of 8" duct...1500 cfm

At the end of that 7" run, add on 10' of 6" flex hose....1160 cfm
At the end of that 7" run, add on 10' of 5" flex hose....1070 cfm
At the end of that 7" run, add on 12' of 4" flex hose.....749 cfm

When I see numbers like this....why would I ever want to reduce the 1500 cfm in my 7" duct down to 750 cfm by choking it to death with a 4" drop? Look at how much more airflow I'd get by running a large diameter pipe right to the tool.

I don't get why people do that.

One other note, running a larger drop (say 6") right to a tool and then reducing it down to 4" to fit an existing port might still be fairly costly. It's best to replace the port on the tool.

In a bunch of days I'll have completed a controlled experiment with my planer (6" drop + 6" homemade hood; 6" drop + 4" factory hood; 4" drop + 4" factory hood), but here's all I have to go on so far:

With the test above with the 12' of 4" flex hose that choked the 1500 cfm down to 749 cfm....when I ONLY had the reducer on the 7" main duct, NO FLEX HOSE, the airflow was an astoundingly low 811 cfm. Just by adding on a reducer! This should be just like the port on a tool. The simple act of reducing the duct may be the single most costly portion of your run. Adding on 12 feet of 4" flex hose only brought the airflow down from 811 cfm to 749 cfm, because the major damage had already been done.

When I know more about this I'll post the results.

Allan

[Bob Johnson2]

Alan,
Excellent info, I'm most interested in your further results. The trick is fabricating bigger diam. ports...

[Scott Parks]

Alan,
Excellent info, I'm most interested in your further results. The trick is fabricating bigger diam. ports...

I think that would be easy. Depending on tool application, you could make one out of left over sheetmetal (assuming you're building a cyclone). Roll a 4" wide strip into a pipe, and bend a flange on it. Then sandwich a flange between two plywood squares with a hole in them the same diameter of your new pipe.

[Allan Johanson]

I'm pretty lazy so I just go to the HVAC parts bin and find a fitting close to the dimensions I want. Then bring out the plywood.

Here's a pic of my new 6" jointer hood. The planer hood I'm working on is a little more complicated, but I'm taking a couple pics along the way to show what I'm doing.

Cheers,

Allan

[Rob Blaustein]

I guess I'd say if your friend is going to go to the trouble of getting a reasonably good DC and setting up ductwork, he might as well make the extra effort and follow the advice given above. For what it's worth, I just converted a Jet 1200 standard DC to a cannister using a Wynn cartridge and plan to follow the advice of the previous replies, going with 6" smooth-walled conduit (PVC) for mains and drops, and even going with 6" flex right to machines when possible. Terry Hatfield and others have advocated (and I know Terry's done this) modifying when possible the dust ports of tools like table saws to accommodate 6" ports--which generally have to be home-made. This is in line with Allan's results above (thanks Allan!)--you take a big hit with reduction.

A general observation: from all my reading on this topic over the past year I get the sense that woodworkers essentially fall into two camps--those who are pretty compulsive about dust collection and those who think others are making too big a deal of it. My impression is that some of the reasons opinions vary so much are: 1. much of the effort is going into collecting dust which we can't actually see and people are not convinced that the invisible dust is harmful; 2. people differ in their sensitivities to dust and some figure if it doesn't bother them, it won't hurt them; 3. dust collection is costly, with costs often far exceeding that of the actual DC (e.g. ductwork, fittings, etc) and many are on a budget and would rather spend money on tools or wood; 4. the topic can get quite complicated and many find woodworking itself is complicated enough; 5. people argue that woodworkers have been doing this for years and they don't see all of their friends keeling over from dust exposure. Yes, some have, but we don't read about epidemics. I'm sure there are many other reasons, and this has all been discussed in recent posts, so I'll stop now.

[Boyd Gathwright]

Hi Jim,

....Here is what I did for my Griz jointer, from 4” to 6”.

http://www.sawmillcreek.org/showthread.php?t=7794

.... and whole system http://www.sawmillcreek.org/showthread.php?t=8070


.... I hope for his sake your friend takes the hint .



Boyd

.

I am about to make some recommedations to my friend about the design and layout of the piping for his dust collector. Now the stumbling point His position is that a 1200cfm dust collector is more than twice the cfm necessary to handle the dust from a Grizz 1023 saw, a X5 Unisaw would perform about the same. He intends to run 20-30' of 4" flex hose to his cabinet saw and branch off to his 8" jointer. He's only talking about using 1 blast gate as the jointer "can't use as many cfm's as the cabinet saw" and that leaves about 550cfm to handle the jointer even with the cabinet saw connected.

I think he is missreading the Grizz information and relying on it to design the piping. Try as I might to change his mind I am having no luck. I think he is making a grave mistake. To further compound his misinformation he is used to using Craftm-ans wet dry vacs up to this point. While they make work effectively up to a point they are not dedicated dust collection sytems. Nor do they move the same cfm' as a dust collector.

I am suggesting that he use 6" metal pipe and fittings to a terminating point at the cieling. Then making his drops, with independent blast gates, in 4" flex or metal pipe.

Any information you have on the subject would be helpful as I am going to probably blamed for not enforcing my suggestions if they are found to be true. It will end up being my fault if his original system fails. Go figure

[Ken Garlock]

Alan,
Excellent info, I'm most interested in your further results. The trick is fabricating bigger diam. ports...

Really Not a Problem (RNAP). I bought 6" starter collars from Air Handling Systems . They are about $5.50 each and are much nicer than the sheet metal stuff you find at the borg. Take a look....

I used the collar to mark the size I needed by placing it over the original 4" outlet on my cabinet saw. I then used a marker pen to draw what need to be cut away. A bi-metal blade in my jigsaw cut out the new hole in no time. The people at Wynn Environmental have some good quality flex hose to make the connection between your ductwork and the collar.

[Debbie Battaglia]

Hi. I'm resurrecting a 2-year old post here, but i have a question i haven't seen addressed. I'd like to install 6" pipe from my cabinet saw and jointer to the DC I haven't yet bought. The problem is that my table saw (Powermatic 2000) has a 4" internal hose running from under the blade down to the 4" dust port. I can enlarge the port to 6", but does that make sense with the 4" hose inside? Powermatic says a) the saw shouldn't run without it, and b) I can't replace it with a 6" hose.

i've spoken with Bill Pentz about this and gotten his feedback, and would like to check here to see if anyone has any experience with this, or any other ideas about the best way to maintain airflow given this situation.

Thanks,
Debbie

[glenn bradley]

Sometimes it's better to just walk away. If your freind is convinced he's working from good data at least 30 feet of 4" flex won't set him back too far. If he's like some folks we all bump into in this world, he'll insist it works fabulous even if it doesn't. I'll hope for a cheap learning experience. Could he move the DC closer to the tools and shorten the runs at least?

[Chris McDowell]

Jim could you convince your friend to get online and do some research on his own? If he is like most of us, he will probably consider changing his own mind quicker than anything you might ever say or do.
When I decided to go with Oneida, it was after a lot of research. I quickly came to the conclusion dust collection is far more complex than it appears on the surface. Unfortunately most of us end up with some type of compromise because we don't have unlimited funds to work with. It shows what a good friend you are to be concerned about his health, but I think Glen may be right. If he's convinced in his own idea, there may be little you can do.

[Ken Deckelman]

Hi. I'm resurrecting a 2-year old post here, but i have a question i haven't seen addressed. I'd like to install 6" pipe from my cabinet saw and jointer to the DC I haven't yet bought. The problem is that my table saw (Powermatic 2000) has a 4" internal hose running from under the blade down to the 4" dust port. I can enlarge the port to 6", but does that make sense with the 4" hose inside? Powermatic says a) the saw shouldn't run without it, and b) I can't replace it with a 6" hose.

i've spoken with Bill Pentz about this and gotten his feedback, and would like to check here to see if anyone has any experience with this, or any other ideas about the best way to maintain airflow given this situation.

Thanks,
Debbie

Debbie,
Welcome to SMC!
You will be better served to start a new thread than to resurrect a 2 year old one that address's a different question, as you can see by the last two replies, people do not look at the dates of the previous post's.

That said, I think I would split a 6" pipe to two 4"ers, one the to cabinet and one to an overhead guard.

[Boyd Gathwright]

Hello Debbie,
.... Welcome to SMC, here's a Ref. for a PM66 saw converted from a 4" to 6" DC. Perhaps this may be of some help http://www.sawmillcreek.org/showthread.php?t=8135

Hi. I'm resurrecting a 2-year old post here, but i have a question i haven't seen addressed. I'd like to install 6" pipe from my cabinet saw and jointer to the DC I haven't yet bought. The problem is that my table saw (Powermatic 2000) has a 4" internal hose running from under the blade down to the 4" dust port. I can enlarge the port to 6", but does that make sense with the 4" hose inside? Powermatic says a) the saw shouldn't run without it, and b) I can't replace it with a 6" hose.

i've spoken with Bill Pentz about this and gotten his feedback, and would like to check here to see if anyone has any experience with this, or any other ideas about the best way to maintain airflow given this situation.

Thanks,
Debbie