Venting DC outside - Thien separator or cyclone?

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Forum topic by mcg1990 posted 10-18-2016 03:02 PM 5069 views 1 time favorited 53 replies Add to Favorites Watch
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159 posts in 2099 days

10-18-2016 03:02 PM

I’m planning to upgrade my DC, like everyone else in this forum!

My original plans had me having to choose between a) build a thien separator, afford a good Wynn filter, or b) buy a dust deputy cyclone, not afford a good filter.

But then I realized I can skip the bags and vent outside! Perfect.

So, while I do have the budget for a cyclone, but is it that much of an upgrade over a thien separator? Anything else I ought to consider?

I plan to collect my chips in a can. So from top to bottom it’ll be the blower from my HF 2hp collector → cyclone/separator → can.


53 replies so far

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Fred Hargis

6321 posts in 3300 days

#1 posted 10-18-2016 03:23 PM

If you intend to vent out, I’d stick with the Thein. Anything it misses will just be discharged out in the air stream.

-- Our village hasn't lost it's idiot, he was elected to congress.

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159 posts in 2099 days

#2 posted 10-18-2016 03:49 PM

True! Last question would be: Is the Thein separator significantly better/different to the bucket can lids you can buy? Example:

I only ask as my shop time is already so constrained, and I suck at making mods and adjustments to my tools. I suppose I ought to see that as an area to improve upon rather than an area to avoid, but…

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Fred Hargis

6321 posts in 3300 days

#3 posted 10-18-2016 03:53 PM

Others with first hand experience comparing the 2 will reply, but to me it goes back to venting outside…in that case, I think either one will do an adequate job. If one separates a little better than the other…so what? It’s all going into the air stream out (and this stuff is biodegradable).

-- Our village hasn't lost it's idiot, he was elected to congress.

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159 posts in 2099 days

#4 posted 10-18-2016 04:11 PM

Thank you for both of your responses.

View scott0317's profile


58 posts in 2262 days

#5 posted 10-18-2016 04:36 PM

I have done what I think you want to do…..i think.

I have a two HP motor from an old harbor freight DC mounted on top of the cyclone. I have a 55 gallon barrel on a harbor freight lift (makes it so easy to empty the container, squeeze the handle and the bin lowers) and this works fantastic. I vent outside and not sure why you would need a filter? If I can help in any way, feel free to pm me.

-- I've almost got all the tools I need, almost.

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13441 posts in 3187 days

#6 posted 10-18-2016 04:51 PM

Build an outdoor chip collector with a chimney for the fines and that’s it. Efficiency of the collector on indoor designs is to prolong filter life. You wont have a filter so efficiency is irrelevant.

-- Rick M,

View mcg1990's profile


159 posts in 2099 days

#7 posted 10-18-2016 08:13 PM

Scott – From what I’ve learned, my new plan is to mount the motor/impeller to my wall, have a 30 gallon can with woodriver trash can cyclone lid, and then vent straight outside.

My shop backs up about 1ft away from my fence, and beyond that is 30ft of trees followed by a car lot. In other words, they can eat my dust!

I’ll update with some pics. All in all I’m pretty excited about this, and wished I had educated myself/requested others to educate me sooner. My suction has been sucking for some time now, leading to frequent blockages at both my jointer and planer. I expect I’ll learn that the problem was a cheap filter bag with an inch thick crust of dust.

I’m ashamed to say I’ve only suspected a gummed up filter bag since last night; about 30 minutes into jointing a pile of 8/4 Oak I look toward my collector to see a ruptured plastic bag and approximately, oh, 30 minute’s worth of Oak shavings spewing into the air like Ol’ Faithful.

View Bill7255's profile


428 posts in 3092 days

#8 posted 11-03-2016 12:33 PM

To answer your question, yes. A cyclone is much improved over the Thien. I have ran both. My estimate is a Thien will capture most of the chips, not all, and little of the dust. A cyclone will capture most of dust and all chips. I was running a Thien with my Jet 1100 and didn’t think it would be good enough for venting outside. I ended up buying the Escarda(sp?) cyclone off eBay and converted a Jet 3hp 1900. Very happy with the results. Here is a link to my setup.

I would recommend a cyclone, but you can try the Thien to see if it meets your needs. One thing for sure is venting outside was one of the best things I did. No filters to clog and reduce air flow.

-- Bill R

View HorizontalMike's profile


7874 posts in 3721 days

#9 posted 11-03-2016 01:22 PM

I use a Thien on a 30gal can with a Wynn filter on the HF dust collector. I am very happy with that. I am in south central Texas and tend to nearly always work in the shop with my 8’x16’ door wide open. Outside venting would create more problems than it would solve, IMO. Best that I can tell, the OP is in the Memphis area and would most likely have many months of mild weather where he too may also work with doors open. That being said, filtering would still be the best option IMO.

-- HorizontalMike -- "Woodpeckers understand..."

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21114 posts in 2663 days

#10 posted 11-03-2016 01:38 PM

I’m glad you asked this question. I’ve intended to do this since I got my DC. Just yesterday I was out there looking at how I would do it. I’d prefer to collect chips outside. I’ve got some 55 gal plastic drums to use. I live in the middle of nowhere so it’ll just be the squirrels eating my dust. If I collect outside, I think I’ll get one of the big trash can top separators you mention. I’ll be following this thread.

-- Bill M. "People change, walnut doesn't" by Gene.

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Gene Howe

12218 posts in 4235 days

#11 posted 11-03-2016 03:17 PM

My separator is a 35 gal. Trash can with a cheap plastic cyclone lid. It does a good job of catching the chips before they can damage the DC impeller vanes.

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

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21114 posts in 2663 days

#12 posted 11-03-2016 03:27 PM

That’s a good point Gene, but I’d sure like to save the space by having the can outside.

-- Bill M. "People change, walnut doesn't" by Gene.

View Woodknack's profile


13441 posts in 3187 days

#13 posted 11-03-2016 03:45 PM

Or buy a new impeller every decade or so.

-- Rick M,

View brtech's profile


1068 posts in 3729 days

#14 posted 11-03-2016 05:28 PM

Hmmmm, lots of thoughts here.

First of all, a “trash can cyclone lid” is not a cyclone, it’s a trash can separator, and it’s probably worse than a Thein in separating chips. Neither do much for dust. A Cyclone is tall, with a tapered cone. They are much better at separation.

The issue with dust collection is suction, which is really airspeed. You want 800+ CFM at the tool to get the “fines” (small dust particles that are the health hazard) out of the tool and into whatever you are sending them. Sending it outside is fine, as long as you understand that your heater or air conditioner will be working overtime. But unless you get 800 CFM or so at the tool, then you aren’t clearing the dust, and you need to use a respirator while you work. The DC is then really just helping things look clean, not be clean.

Venting outside is good for airspeed because you don’t need a filter and filters cause back pressure and thus drop CFM. Any DC without a filter is going to work better than the same DC with any filter.

But you have to start with enough CFM, and then not lose it somewhere. The usual calculations say that with a good quality cyclone and a good quality filter, you need 5 HP and a 15” impeller to get 800 CFM with a typical 6 inch main line and well engineered drops. Without the filter and without the cyclone, you could maybe get it with 3HP, but there are a lot of variables, so maybe, maybe not.

But if you start at 1.5 HP or even a honest 2, then you can’t get there. If you start with 2.5 or 3 HP, and add a poorly designed separator, you probably can’t get there. Have to say “probably” because there are a heck of a lot of variables.

You can measure CFM, so don’t guess.

Separators are a nice to have. If you are venting outside, you will get a pile of chips and dust near the vent that you probably want to clean up. A separator will cut down how often you need to do it, and how much work it takes to clean up. That’s all they do, make it easier to clean up. This comes at a cost: they introduce loss of suction. A better separator gets more stuff out of the airstream at a lower insertion loss of CFM. The very best still have loss, and still allow some dust to get through.

Generally, a well designed cyclone is the best, but a well designed cyclone is big, and needs a big motor. A trash can separator is usually the worst. The Thein baffle and less well designed cyclones tend to be about the same, but there are some fair to middln smaller cyclones that can out perform a Thein baffle. The Thein beats the really cheapo cyclones.

So, if you have 3HP or so, and 14 or 15” impeller, then adding a decent cyclone will make it easier to clean up the mess where you vent outside and you still will be able to clear the fines. Not much else can do that; if you drop below 2.5 or 3HP, even with no separator, you probably can’t get to 800 CFM at the tool. 2HP with a Thein or cheap cyclone won’t do it, and it’s worse with a trash can separator.

If you are okay wearing the respirator all the time when you generate dust, then these issues are much less of a problem, and then you back to ease of cleaning up. The Thein is the best bang for the buck, but a cheapo cyclone will be okay. I’d avoid the trash can separator if you really are trying to be efficient.

And we have not even started talking about ducting!

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10859 posts in 2293 days

#15 posted 11-03-2016 08:40 PM

I have a HF top hat on a 55 drum with top closed off and a 4” pvc 90 in the middle. The lid of the drum is a thein baffle. Works like a champ.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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