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Dust Collection Confusion

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Forum topic by rsdowdy posted 07-11-2011 10:10 PM 1358 views 0 times favorited 7 replies Add to Favorites Watch
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rsdowdy

105 posts in 2659 days


07-11-2011 10:10 PM

About to bite the bullet layout dust collection pipe instead of moving a hose from machine to machine. I understand it is best to have the largest volume pipe your collector will pull air through to, and set up as close to your dust making machine as posible. If you are going to have only one machine operating at a time that will use a 4” pull at the machine, what good would a 6 inch pull from the collector do for you, if you can only pull 4”s of air? So wouldn’t it be better to set up with 4” pipe vs 6” for a home setup with the understanding you are only going to have one machine operating at a time? And if all you are pulling is 4”s of air into a 6” pipe, wouldn’t that actually slow up the air stream as your 4”s being pulled from the machine gets pulled into 6”s of air in the pipe? And if all of that is the case, if you use 6” pipe, then wouldn’t it be best to have another gate partially opened at another machine so you will get close to 6”s of air pulling through the pipe?

Thanks for your help!

Royal


7 replies so far

View David Grimes's profile

David Grimes

2078 posts in 2103 days


#1 posted 07-11-2011 10:15 PM

What DC do you have ? What machines ? Are you inferring that you use a shop vac hose from machine to machine now ? or are you using Rockler Dust Right ? or other ?

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

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rsdowdy

105 posts in 2659 days


#2 posted 07-11-2011 11:04 PM

I have one of them Harbor Freight “2HP” Dust Collectors currently and use the Durt Right Hose to move from Machine to machine. I have a Grizzly G0691 3HP 220v Table Saw, Grizzly G0490 8” Jointer, Grizzly G1035 1 1/2HP Shaper, Dewalt DW735 13” Planer, PC 7518 Router about to go into a dedicated Router Table (once I build it), and a Chop Saw.

The hand held power items I will just use a shop vac for.

Suggestions?

Royal

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Manitario

2399 posts in 2346 days


#3 posted 07-11-2011 11:27 PM

Dust collection can be broken down into two components; chip collection and fine dust collection. Most home DC’s achieve good chip collection and mediocre fine dust collection. Chip collection is mostly a function of having high air speed; fine dust collection is more a function of air volume ie. the “CFM” number you’ll see thrown around. Minimal CFM for fine dust collection is 700-800. Now, here’s how it breaks down with regard to your questions. CFM is drastically affected by the static pressure of the system ie. the “friction”. Using a larger diameter pipe will reduce the overall static pressure of your system, and keep your CFM up; yes, you’ll take a hit with having only 4” ports on your machine, but less so than if you used 4” for the entire system. The other issue though is that airspeed, and therefore chip collection is increased by using a smaller diameter pipe (to a certain extent, similar to putting your thumb over the end of a garden hose to spray water). By having a 4” port connected to a 6” pipe, you’ll lose airspeed and may end up with chip clogs if your DC is not powerful enough, or if you have long vertical runs (eg. your ducting at the ceiling).Your best solution would be to swap out your 4” ducts on your machines for 6” ports; however, if that is not an option, I’d just use 6” pipe for your mains and transition down to 4” right at your machines.

-- Sometimes the creative process requires foul language. -- Charles Neil

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Alan S

178 posts in 2780 days


#4 posted 07-11-2011 11:30 PM

I have yet to setup my permanent dust collection ducting, but I have been planning. I believe you are right. It is not a good idea to use 6” ducting then narrow it down to 4” going to one machine because the air will slow down when it hits the 6” tubing. My plan is to run 6” around my shop and everywhere I have a drop, use a 6”-4”-4” Y connection. My blast gates will be 6” and only one 6” port will be open at once. This way, the two open 4” ducts will allow enough airflow to sustain speed in the 6” pipe. I will try to use both connections for each machine: the tablesaw will have an underneath connection and an overhead connection.

Alan

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rsdowdy

105 posts in 2659 days


#5 posted 07-18-2011 08:54 PM

Thanks for the info everyone. I have been over at Bill’s site and am planning to go with the 6” pipe in the next few weeks when I can get around to it.

Royal

View crank49's profile

crank49

3981 posts in 2434 days


#6 posted 07-18-2011 09:56 PM

The HF 2 hp is designed for a 5” inlet. Your 6” plan will result in slightly lower FPM velocity in the big pipe. The HF will handle a 5” best, but a combined 4” and 2-1/2” works very well too. That is the arrangement I have used for several months.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

View David Grimes's profile

David Grimes

2078 posts in 2103 days


#7 posted 07-19-2011 02:00 AM

Ditto 4” and 2 1/2” with HF 2 hp… very good results.

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

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