# Dust Collection Question



## twoblacklabs (Jan 12, 2011)

Maybe this is a stupid question that has been answered over and over but I can't find a logical answer. If one adds a chip separator (typical hf 2hp dust collector setup), why in the world do you STILL need a collection bag? It seems to me that it already HAS a chip separator as the chips fall into the plastic bag.

Would someone please explain the advantage of adding a separator up stream of the collector itself and then having a bag?

Thanks for the enlightenment.

John


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## JoeLyddon (Apr 22, 2007)

Good question…

In my case, I have a filter in my Shop Vac that is absolutely USELESS because of the Dust Deputy in front of it… besides being there in case the DD filled up & the stuff had to go somewhere… (??) I will never have to buy another Filter bag for it!


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## Holbs (Nov 4, 2012)

Using a separator does the job upon chips and large dust particles. Depending on the item (Thein baffle or dust deputy or such), you could get 80-90%, as it was designed to do. But what it's not designed to do is capture 100% fine dust that does get thru to your bag/filters. I have a top hat thein baffle and dual wynn filters on my grizzly 3hp for that reason.


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## wapakfred (Jul 29, 2011)

What Holbs said: thinking it will get everything will simply fill your shop with the finest dust particles. But what it does allow is to vent outside (if other conditions, like heat loss permit) in which case the fine particles will be scattered by the slightest breeze to parts unknown (or your neighbors black Mercedes).


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## twoblacklabs (Jan 12, 2011)

That all makes sense but my confusion remains. Maybe I need to say it a different way.

In a single stage dust collection system, the chips and dust come into intake and then begin to spin in a conical fashion, dropping the chips into the collection bag while the filter bag grabs the dust (in my case, up to 5 microns) which build up on the upper filter bags walls, creating a "thicker" filter. When the system is shut off, the loose dust ALSO falls into the lower collection bag. Turn it on and the cycle begins again. Thus, the chips and a large amount of dust collect in the lower collection bag. You then must change out the bag as needed.

In my mind, I see the add on cyclone, chip separator (or whatever one chooses to use) doing essentially the same thing. The rotating air flow with the aid of gravity, drops the heavier particles in the add on chip collector. The lighter, fine dust continues to the upper filter bag/cartridge. Once the unit is turned off, the floating fine dust would in turn, drop down into the existing collecting bag. Thus, essentially , the exact same process has happened.

What I can't grasp, is why we would want to go to the trouble of adding the cyclone/separator/dust deputy (etc). Clearly, others have understood the benefit but I am missing it. There has to be a simple explanation. Obviously I'm thick headed because I can't figure it out. Other than a convenience of not having to unlatch the metal band that holds the original collection bag, pulling the plastic bag away, what is the benefit?

It's not a matter of "if you don't want it, don't do it". I'm seriously trying to understand this as it's been bugging me for awhile.

Thanks for helping.
John


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## dodahman (Jun 12, 2012)

>>>>What I can't grasp, is why we would want to go to the trouble of adding the cyclone/separator/dust deputy (etc). Clearly, others have understood the benefit but I am missing it. There has to be a simple explanation.<<<<<

I think in this situation, the chip separator is used because it's MUCH easier to empty and set back up than the bag attached to the HF dust collector. The bag then would be left for back-up and may only need to be emptied monthly or yearly or never (depending on usage).

It also keeps large pieces and nails and nuts and bolts from going thru the impeller.

peace, T


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## wapakfred (Jul 29, 2011)

^^^^^^^^ there ya' go. In the case of a cyclone, a well designed one will actually separate out much of the fine dust so it never gets to the filter, insuring you have maximum air flow for a much longer time. A less well designed one still drops some of the fines into the bag, but not all. Also, if you have a cyclone, the impeller doesn't have to be built to withstand impacts of chunks, so they can be of a lighter, more aerodynamic design.


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## Holbs (Nov 4, 2012)

A separator does 3 main purposes: saves the dust collector impeller from damage (as heard in my test run video below), saves wear & tear on my $300 air filters, and easier to unload 55gallon plastic bin than the dust collector bags themselves.





View on YouTube


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## twoblacklabs (Jan 12, 2011)

Thanks for all of the replies.

Preventing impeller damage seems to be the biggest advantage with the additional ability to empty into something other than the collection bag.


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## Rentvent (Jan 28, 2016)

If you have a decent separator in front, you don't need the lower clear plastic bag anymore.

http://lumberjocks.com/projects/106615

There's also youtube videos showing the bottom bag replaced with a round piece of plywood.


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## JoeLyddon (Apr 22, 2007)

It's EASIER to empty a Dust Deputy bucket than a Shop Vac and it's Filter… BY FAR!

My Filter bag doesn't look like it has caught much dust at all!
... it still SUCKS BIG TIME!

SUCKS GOOD and STRONG, it seems forever… NEVER dropping because of a clogged Filter, etc. etc.


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## MJCD (Nov 28, 2011)

twoblacklabs:

There are several advantages to the pre-impeller separator… and damage to the impeller, though a possibility, is not the most important - IMO.

1) Cyclones provide for a more efficient air stream - which is why a Thein separator has a lower separation efficiency than say a Super Dust Deputy (SDD) or a full cyclone system.
2) Removing the chips earlier within the air stream means that the impeller has less debris to move, overall - think of it in terms of debris-feet (how many feet are you moving an amount of debris - something like 100 people on an airplane flying 100 miles is 10,000 passenger miles); and there is less air turbulence (technically, less 'static pressure loss') going through the impeller - at this point, it's probably some fraction of 5 micron dust.
3) Some element of the really small stuff still gets through; and if there's a clear plastic bag to collect it, well, that's good; otherwise, the extra stuff ends-up in your filters - Clearvue designs-in a 'catch-box' at the bottom of the Wynn Filters stack - mine accumulates stuff when I forget to change my primary dust bid.

I've owned the SDD, and it's excellent - it does limit you to a 4" or 5" main run, which in-turn limits you to drawing from one machine at a time. That said, they are worth the money.

MJCD


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## Puzzleman (May 4, 2010)

Joe said it best of all. The reason for adding a dust separator is that the suction does not decrease as the dust builds up. Having it easier to empty the dust bin is a plus, but the main thing is that you have maximum air flow through the suction tube. This is what catches all of the dust.

As far as a filter afterwards, the filter catches the 5% to 10% of fines that are not caught by the separator.


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## Rob_s (Sep 12, 2016)

For me, the benefits on a shop vac seem silly, while the benefits on a true dust collector are pretty tangible.

Adding a cyclone to a shop vac results in me emptying a bucket-type vessel, which I would do with a shop vac anyway, at the cost (time, money, or both) of all the hardware required and the added bulk. I'd rather just keep a supply of filters on hand, personally. Just doesn't pan out IMO.

On a larger true dust collector, you're talking about emptying a bucket vs a bag (bucket is easier) as well as reducing clogs and extending life on a much more expensive filter, or not having to deal with a filter bag. Not to mention protecting the blades as already noted.

It occurs to me, as I write this, that a shop vac already operates as somewhat of a cyclone as the dust is sucked into the vessel, not through the fan.


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## JoeLyddon (Apr 22, 2007)

> For me, the benefits on a shop vac seem silly, while the benefits on a true dust collector are pretty tangible.
> 
> Adding a cyclone to a shop vac results in me emptying a bucket-type vessel, which I would do with a shop vac anyway, at the cost (time, money, or both) of all the hardware required and the added bulk. I d rather just keep a supply of filters on hand, personally. Just doesn t pan out IMO.
> 
> ...


Robs… You obviously have NOT tried it… Try it, you will LOVE the FULL SUCTION mode ALL of the time… and NOT have it get weaker & weaker as the filter gets clogged up…


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## bkseitz (Oct 24, 2014)

John,
The simple answer is that while almost all / all the chips get collected by the separator the finer dust will manage to get through. Thus a fine filter and bag/box are there for that. I've a mobile 1hp Rigid I'm working on to replace with a HF 2HP with a Wynn Filter and Super Dust Deputy.

The Rigid was connected to one of those trashcan lid separators. It worked o.k. considering. However, the bag still collected fine dust that also bled out of the bag-[5 micron?] This is why I'm working to replace it. In the meantime I've doubled up on protection using a 3m 7500 Dust Mask also


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## Rob_s (Sep 12, 2016)

> Rob_s… You obviously have NOT tried it… Try it, you will LOVE the FULL SUCTION mode ALL of the time… and NOT have it get weaker & weaker as the filter gets clogged up…
> - Joe Lyddon


Correct, I have not. I started to assemble the parts to do it and then realized I was trying to fix something that isn't broken with a solution that costs more money and shop time with no appreciable benefit. Right now in my shop vac I have a filter bag and a filter and never notice a loss of suction when it's full nor a big boost in suction immediately after emptying.

Everyone has their priorities. Making my shop vac bulkier, more complex, and more expensive while consuming scarce shop time to do so just isn't very high ton my list of priorities. Especially when I expect to have a larger dust collector by the end of the year. I'd rather sinc my shop-vac-upgrade budget into getting a better dust collector and the time spent into assembling said collector.


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## JoeLyddon (Apr 22, 2007)

Rob_s… To me, a Shop Vac working alone with it's filter, *is a broken system…*
... once you Try it… guaranteed, you will LIKE it… and it doesn't cost That much more… I got a Dust Deputy on sale a few years ago… IIRC, maybe $50 or so… Worth every penny…

How many filters can you buy for $50? I have NOT bought ONE filter since I have been using this Dust Deputy.
... cleaning those filters, to me, is a real pain in the a$$...

Have fun…


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## brtech (May 26, 2010)

I still think we haven't answered the question.

If you start with a DC that is designed with a simple ramp separator and a bag, and you put a different, hopefully better separator in front of it, then you don't NEED another separator, but it's close to impossible to get it out of the airstream. You would have to modify the sheet metal to push the air from the impeller directly into the filter. If you just block it off, the ramp will probably screw up the airflow pattern (haven't tried it).

But, then you create another problem - you need to be able to clean the filter. It's mighty convenient to be able to drop the dust down from the filter to the bag.


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## JoeLyddon (Apr 22, 2007)

Wouldn't you just have to design (buy) something, on a larger scale, like a Dust Deputy?

I can't see it being any simpler than that… (???)


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## ToolCaddy (Dec 10, 2015)

I am most interested in controlling the fine dust that is a product of nearly all milling activities in my wood shop. I can sweep up chips but my cyclone separates and catches most. When I inhale the fine particles, I am not able to exhale them. When I clean my filter, it is absolutely full of the fine dust that can cause disease. The cyclone just makes my final filter more efficient.


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## sawdustdad (Dec 23, 2015)

I have a 30 gal trash can separator at my 20 inch planer, which, of course, makes 90% of the chips/sawdust in the shop. This can is easy to grab, carry outside and dump. The rest of the system drops go directly to the DC and into the bag/filter. Jointer, shaper, TS, drum sander, disk/belt sander, band saws, etc.

If I didn't have the separator at the planer, I'd be removing and reinstalling the DC bag constantly. With the separator, I can go weeks or months, depending on my projects, before I have to dump the DC bag.


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## kelvancra (May 4, 2010)

Because I have a Oneida cyclone in front of my four bag collector, I could get away with a six inch deep bag, rather than one three feet or so deep.

The cyclone makes such a HUGE difference, I put wheels on both my cyclone and my collector and use it to vacuum the pine cones and leaves in the yard. As already pointed out, the mean stuff gets spun out before it can damage the impeller.

I even used the contraption to vacuum all the paint chips painters left on the gravel at my wife's store. I picked up about a gallon of gravel, but none of it went through the collector.

Add to all the foregoing, the cyclone spins out so much of the fines I only have to empty the bags on my big collector every few years.

http://lumberjocks.com/topics/125546


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