Shop Notes #13 Dust collector, has anyone had any experience with it?

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Forum topic by Straightlines posted 08-30-2014 01:23 PM 1607 views 0 times favorited 4 replies Add to Favorites Watch
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70 posts in 2098 days

08-30-2014 01:23 PM

Topic tags/keywords: dust collector shop notes 13

The title says most all of my question. I’m waffling between the Shop Notes design and modifying it to be a Thien collector instead of a cyclone, but the rest of the design would be pretty much the same. I am hot-rodding my HF 2hp DC.


-- Cut twice, measure once ... DOH!

4 replies so far

View timbertailor's profile


1594 posts in 1628 days

#1 posted 08-30-2014 02:17 PM

I am building my cart now. I have finished the Thien Cyclone portion of the project. I will post some photos hopefully be the end of the holiday weekend. Hope to incorporate a place for vacuum hoses, air hoses, fittings, pipe clamps, bar clamps, more clamps, shop vac and its hoses, adapters, etc.

My feelings are, if it going to take up space, I am going to make the most of it. Usually means going vertical. I am eliminating the plastic catch bag, running the motor directly into the filter inlet, and running 5” hose directly into the Thien Cyclone. I am running 4” out of the trash can. I bought the 0.5 micron filter from Wynn Envirnomental. The 80\20 filter weave blend.

-- Brad, Texas,

View crank49's profile


4032 posts in 3175 days

#2 posted 08-30-2014 05:08 PM

Other than the Thein (or any cyclone) cutting the available static pressure in half I’d say you have done about all you can to that unit. The filter cartridge and the direct connection to the filter module will help offset a portion of that loss.

A simple drop out container near the dust source , table saw or jointer for instance, would get you about 90% of the collection ability of the Thein or the cyclone with much less penalty in terms of static drag.

Bottom line is this. The HF collector does a pretty good job as it comes off the boat, but it only collects particles down to about 5 microns. The really dangerous dust particles are less than 1 micron, so the filter media does need to be improved. You did this with the 0.5 micron cartridge. That cartridge has 10 times the filtering ability and also has about 10 times the surface area so in terms of static resistance it is almost a wash. The big difference is that fabric bags get blinded; dust particles get embedded in the fabric and increase the resistance to air flow fairly quickly. The dust particles tend to collect on the surface of cartridges so it is easier to knock them off.

The other problems with the HF collector are that it is a pain to dump the plastic bag and the fan is before the filter. Everything that gets sucked up goes right through the fan. These problems are pretty much common to all the single stage bag type filters.

To address these other problems, many people add a cyclone, or a Thein separator, in line before the fan. This works to catch about 97% of the dust before it gets to the fan or filter and drops it into an easily emptied container. But, cylones and Thein separators have their own problem. They are static pressure hogs. For the devices to work they have to generate very high centrifigal forces. They do this by forcing air flow into a vortex at very high velocity and then extract the air flow from the center. It absolutely works, but it uses up a lot of available pressure, up to 5 to 7 inches, to do so.

A better solution for the HF collector, which is a little short in the pressure department anyway, is to use the above mentioned drop out. This is just a container, 30 gallon metal trash can will work, with two connections on the lid. Dirty air enters one side and the velocity drops because it is a large area and then the other connector is where the clean air exits and goes on to the fan on the collector. The only static pressure loss is to re-accelerate the flow inside the container and that is only about 1 to 2 inches of static.

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1594 posts in 1628 days

#3 posted 08-30-2014 06:58 PM

I looked at both solutions and weighed the good and the bad, as well. It seems adding the better filter makes up for the pressure drop created by the Thien. I get better life from the motor\fan because more of the waste is being removed prior to entering the motor\fan than a drop out solution.

I did not use the plastic bag on the bottom of the filter either. It is a waste of space, and as you mentioned, a pain to service. I just added a drawer to collect what little actually accumulates. I now store the shop vac under the Wynn filter where the bag once sat.

-- Brad, Texas,

View Straightlines's profile


70 posts in 2098 days

#4 posted 09-03-2014 04:54 AM

Hey Brad and Michael, thx I appreciate your replies. Since Martin & Ms.Debbie have left the bldg, my account has been in suspense for months and I have been able to post things of my own. This OP was sent in many weeks ago, and since then I have completed my Thien separator build. It works well, although I’m not using any filter media since I work in my driveway for the next few months. Once I get into a structure, I’ll be revisiting the filter media, and with that in mind, I’m adding some thoughts I had after my initial build which I posted over at SMC for some folks who were on “spin cycle” WRT DIY DC setups:

“1) The bare impeller/motor combo moves a certain amount of air.
2) Every little thing that gets added to the inlet or outlet side of the fan is going to reduce its performance, and each of those additions has its own value that is literally subtracted from the original performance value—these reductions are basic physics.
3) Filter media restricts airflow and therefore #2 above applies to it; greater levels of filtration subtract more and more airflow, which represents lost performance. That is why the cheapo setups include 5 & 30 micron filter bags—they flow better than the filters that trap the really harmful particulates.
4) There is an optimum area of any filter media for a given air flow: Too much air coupled with inadequate airways out, and the particulates get forced into the media itself, which clogs, and ultimately gets blown to pieces and fails; too little air flow and the system just won’t suck adequately. This is why the better levels of filtration need to be bigger so that there are more smaller airways (which are more restrictive) to adequately pass/exit the given volume incoming air from that fan unit.
5) Pleated/canister filters exist because they take up less space than shaker bag filters. They cost quite a bit more too. Before buying that canister filter, you’ll have to decide just how important that reduced size actually is to you.
6) Canister filters clog far faster and easier than shaker bags, because those pleats concentrate and trap the dust laden air in very tight little pleated corners.
7) Canister filters are not easy to clean.
8) If you have enough room for it, the best value for performance is a 1 micron (.5 micron appears to be available now) shaker felt bag. These take up a lot more space than the canister, but as the name indicates, only require that the bag be shaken in order to clean it. They are 1/2 the cost of the canisters, and can be custom configured at little to no additional cost so they will work with ducting that places them in more convenient locations.

As numerous others have stated, a separator is essential. If I were doing it all over again, I would buy a HF 1hp – 2hp DC (~650 cfm and as low as $99) + 1micron (.5m) bag from Rockler ($25 on sale now) + a Dust Deputy (on a big can) and use a hose no longer than 6’ – 7’. This would all be cart mounted and moved from machine-machine and should be able to keep a TS or planer clear. The cost of this healthy setup would be about $200. Ducting is the real hidden expense in DC systems, and my approach 100% eliminates it; plus if and when you tire of moving the dust cart around a big shop (jeez I wish I had that problem), then just add another one to the other side of your shop to ease the carting about and you will still be more than $1K – $2K richer.”

Well, that’s the theory I’m hoping will work. Michael, the “shaker” felt bags/sleeves should work without “blinding” and the fact is that when they are sized correctly, the air velocity is sufficiently reduced to work w/ the singeing to create the dust “cake” that ultimately delivers the final level of filtration (.5m). Further, the “shakers” are designed to be simply shaken for cleaning, hence the name. Unless there are really significant space restrictions, industrial applications use “shaker” felt because of the ease of cleaning and maintenance over cartridge filters, hence the building of bag houses. Don’t get me wrong, I don’t have a problem w/ cartridge filters, but I will do everything to avoid using them because of the 200% cost penalty + the onerous cleaning regimen associated therein (yes I have cleaned cartridge filters many times (HEPA on shop vac, K&N on motorcycle)).

-- Cut twice, measure once ... DOH!

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