a Thien seperator plate

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Project by Mainiac Matt posted 08-19-2012 08:37 PM 5423 views 1 time favorited 12 comments Add to Favorites Watch

I’ve been fixin’ to put a Thien style plate into my single stage Grizzly canister DC…. but it hasn’t risen very high on the priority list…. untill I emptied the bag and took a look up inside the filter the other day….

Yikes! what a mess.

So after spending the better part of an hour outside wit an air hose cleaning the filter, I decided now was the time.

One measurement (inside diameter) was all I needed… and I drafted up the “standard” thein plate geometry. and cut it out of a piece of 1/2” salvage particle board.

I drilled three holes in the side wall and then applied some foam gasket tape to the short (120 degree) section of the seperator plate and attached it to the wall with three pan head sheet metal screws.

Then I scrounged up a couple long 1/4-20 binder style bolts to support the other side.

And in keeping with tradition, I decorated it with a Killroy charicature.

Now to fill up the bag and inspect it to see how well it helped to keep the filter canister clean.

Happy Trails….

-- I yam what I yam and that's all what I yam

12 comments so far

View BigDaddio's profile


19 posts in 3636 days

#1 posted 08-19-2012 11:33 PM

I don’t really understand the point of the plate, Looks like a good idea and as I have a similar collector I’d be interested.


View Mainiac Matt 's profile

Mainiac Matt

8557 posts in 2530 days

#2 posted 08-20-2012 12:25 AM

Normally these plates are used on cyclone seperators which are placed in the main branch b4 the blower…

But they can also be placed in the discharge to aide in separating the debris in the bag from the filter …

As the chips and dust are spun around the cylindrical chamber they fall out of the stream into the bag, and the slower air in the center can no longer entrain material as it goes up the larger diameter hole into the filter.

Or that’s the idea at a least!

-- I yam what I yam and that's all what I yam

View thedude50's profile


3603 posts in 2679 days

#3 posted 08-20-2012 03:40 AM

I am curious how this effects the suction on the system.

-- Please check out my new stores and

View Mainiac Matt 's profile

Mainiac Matt

8557 posts in 2530 days

#4 posted 08-20-2012 01:20 PM

Hey ‘Dude’...

I don’t really have any way to measure whether or not there’s a change to the air flow…. other than to stick my hand up to the pipe…

I fired it up last night to make some cuts on my miter saw and the air flow to my “hood” felt strong.

But since I just cleaned the filter thoroughly, that’s to be expected with or without the plate…

There’re several write ups on these plates out there…. here's one

-- I yam what I yam and that's all what I yam

View GregD's profile


788 posts in 3337 days

#5 posted 08-20-2012 01:33 PM

I did this same thing to my DC.

I waited too long to empty the bag and still got a bunch of stuff inside the filter. Further, just before I emptied the bag, I was doing raised panels on my router table that generated a lot of fluffy shavings that clumped inside the router table, and I stupidly sent those clumps into the DC.

I’m not very far along on my second bag so I can’t yet tell how much this helps.

But I still expect to need to clean the filter, probably each time I empty the bag. But maybe the airflow won’t drop off as much as it did between cleanings.

-- Greg D.

View Mainiac Matt 's profile

Mainiac Matt

8557 posts in 2530 days

#6 posted 08-20-2012 02:00 PM

I’m re-using the clear (~6 mil) poly bags that came with the DC….

I should mark a line at about half full with a sharpie as a reminder.

I’m not at all interested in cleaning the filter with every bag change…

I’ll build a trash can top hat pre-seperator b4 I go there.

-- I yam what I yam and that's all what I yam

View Milo's profile


869 posts in 3520 days

#7 posted 08-20-2012 05:43 PM

Huh. Haven’t seen it set up like that before… Interesting. I use a separate canister for my separator. So the point is to keep stuff out of the filter is it? Huh. Learn something new every day! Thanks for sharing!

-- Beer, Beer, Thank God for Beer. It's my way of keeping my mind fresh and clear...

View Mainiac Matt 's profile

Mainiac Matt

8557 posts in 2530 days

#8 posted 08-20-2012 06:09 PM

Well….. that’s the idea… we’ll soon see whether or not it works.

-- I yam what I yam and that's all what I yam

View crank49's profile


4032 posts in 3172 days

#9 posted 08-20-2012 06:14 PM

In a true cyclone, the walls are tapered into a cone with a dust outlet at the bottom.
Air enters the top of the cone and accelerates as it is forced into smaller and smaller circles as it moves down the cone.
At some point the dust and particles are separated from the air stream by centrifugal force and flung out to the cone wall while the lighter, clean air spins back up the center of the vortex to exit out the center of the top.
The Thein seperator mimics this action with a baffle and avoids the necessity of making a cone shape. The dirty air is spinning down and through the open slot side of the baffle and it depends on the closed part of the baffle to replace the cone function of letting the particles drop out of suspension before the lighter clean air goes back up the center.

In either system, the more pressure drop you create in the system, the cleaner the exit air. I don’t know if it’s possible in a Thein system, but in a cyclone with 16 to 20 inches of pressure drop it’s possible to capture smoke particles, below .1 microns. But it’s cheaper to capture smoke in a cartridge or bag filter with less pressure drop. The energy to create pressure increases as the cube of the pressure difference. In other words, to double the pressure will take 8 times the horsepower.

View Mainiac Matt 's profile

Mainiac Matt

8557 posts in 2530 days

#10 posted 08-20-2012 07:39 PM

I wish I had got involved with woodworking boards and learned more about DC systems a long time ago….

I had salvaged an industrial cyclone with a 3 HP 3 ph motor and always intended to set up a rotary phase invertor to run it. This unit was stuffed into the corner of my shed for years. But when I abandoned the phase invertor project (for fear I would burn my house down and then have the insurance co. deny my claim) I carted the entire rig off to the recycled metal bin at the town dump.

I wish I still had that cyclone and could plumb it to my current Grizzly DC….

Oh well…. live and learn.

-- I yam what I yam and that's all what I yam

View Newbiewoodworker43's profile


151 posts in 2644 days

#11 posted 03-14-2014 09:20 AM

I am working on putting a Thein plate in my Delta 50-850. How far below the conical part of the DC did you put the plate?

Also I was wondering how it has been working for you? Did you keep it in place or switch to a Thein seperator?

-- ---Howard, Amesbury MA

View Mainiac Matt 's profile

Mainiac Matt

8557 posts in 2530 days

#12 posted 03-14-2014 02:04 PM

Hi Howard….

Yes I’m still using the plate and it is doing a good job of keeping debris out of the pleated filter.

The picture you see above is taken from the bottom side, as the plate goes below the inlet.

As best as I understand, this is how the plate works. When the air is moving fast, centrifugal force keep the entrained wood waste around the outside perimeter. As the air slows, it drops this material and cycles in and up.

The plate helps keep the material in the bag, so it doesn’t get stirred up into the pleats.

A Thein separator in the intake line will protect the impellor by removing the material before it goes into the impellor and it should be easier to empty the can than the bag. It should also keep your filter clean, as less material makes it into the DC.

BUT…. it does take up a lot of space, which I don’t really have. And the impellor on my Griz is fabricated with quite thick steel plate, and I don’t typically suck up a lot of chunks. So for now, the plate is the solution for me.

With this style DC, mounting the motor to the wall, so you can put the pre-separator below it is the best way to get a compact solution with a pre-filter. But that’s a lot of work and my existing set up is meeting my needs just fine.

-- I yam what I yam and that's all what I yam

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