To preserve suction and reduce the cleaning of filters and containers of dust removal systems, you can add a pre-vacuum separator. It removes large and (when done right) even small visible particles before they get to the shop vacuum.
Note that it is generally agreed that no separator removes the finest of invisible particles and a hepa quality filter and/or proper dust mask is still recommended if breathing the exhausted air from the vacuum, especially if fine particles may be present from sanding, drywall, or hazardous materials.
In a recent test, my own version of a Semi-Thein-Clone performed as well as the manufactured Oneida Dust Deputy, and out-performed it in suction tests. (see more here)
And since it is so easy to build in comparison to the more complicated Thein Baffle, I thought I would give a quick step-by-step on how to build it.
My Semi-Thein-Clone is so named because it isn't quite a Thein Baffle (so named for the guy who first made it), and it isn't quite a Cyclone, but it uses parts of both.
It isn't a Thein because the baffle is not high up to the in/out and has more than one single slot, however the bottom of the bucket with slots acts similarly to a Thein by dropping the debris out of the turbulent air flow through slots and keeping the turbulence mostly out of the lower container. This prevents debris from getting churned up and returning to the air-flow.
It isn't a true Cyclone because it lacks the conical shape that the cyclones use to drop the debris through a central hole, however, it does use the longer spinning force and a extended center out-flow to create a cyclone like effect that forces the particles out of the airflow against the sides of the bucket and drop down through the slots.
Estimated cost of Collection Container: $27 to $30
Estimated cost of Semi-Thein-Clone: $10
- Collection container of some sort (20 gallon is a great size)
- Plywood or other flat board wide enough for the top of your collection container (I used well sanded OSB)
- Thick foam weather stripping to seal between the wood and the container
- 3.5 gallon bucket (I found a transparent one at Lowes even if it is slightly offensive by being pink)
- Bucket lid
- PVC... 90 degree elbow, three straight connectors, 8 to 10 inches of PVC pipe
- PVC pipe and/or connections that can be made to connect to your shop vac hoses (they may need sanded to reduce or wrapped with tape to increase)
First, prepare your collection container...
Many people use plastic barrels or metal trash-cans for this, however, with the potential of collapse from suction, it seems that re-enforcement is often needed. You can use whatever you want, but I chose to go with a sump-pump basin. It is surprisingly strong and equally surprising that it cost the same as a metal trash can of the same size. It will need no additional support to prevent collapse, however, it is heavier than a standard trash can.
Cut a lid to fit or overlap as needed. Sand smooth and add thick foam weatherstrip to create a seal between the lid and container. You want this lid to seal well, but be easily removed to dump the collection container. To get a good seal at the end point of the weatherstrip, cut the ends with a bottom half and a top half that will overlap.
Make the Semi-Thein-Clone...
Trace the bottom of your 3.5 gallon bucket onto the lid (it doesn't really need to be centered, but looks nice that way). Cut out the circle and sand if needed to fit the bucket base tightly into the hole.
Cut 3 slots into the bottom of the bucket right at the edge. My slots are around 3/4 to 1 inch wide and take up about 2/3 of the bucket bottom edge... anywhere close seems like it would work equally well. While these slots obviously don't need to be perfectly spaced, having them even would look nicer and provide even support for the bottom of the bucket. Mine are a bit random but work fine. To make these slots, I used my palm router, but you could use pretty much any cutting tool. Use a little sanding paper to smooth the cut if needed.
NOTE: It is very important to cut the slots right against the edge of the bucket side. The debris needs to fall straight down the sides into the collection and will kick back up if it hits a ledge.
Then use some type of glue to seal the bucket base into the wooden lid. Caulking may give the best seal, but I used hot-glue. It could be heated if needed to be removed or something later. (I would use caulk if I did it again)
Now Prepare the Lid...
Cut one hole in the center of the lid that is just barely larger than the PVC pipe. I used a hole saw, but you could use a jigsaw or other cutting device. Then cut another hole about a half inch inside the bucket edge. Cut two 1 inch rings of PVC to bridge the gap between your fittings
I then cut a little foam gasket to work as a seal while testing the system, but you can skip this step and move to gluing things into place.
Put a PVC ring you cut through the center hole and attach straight connections on the top and bottom with PVC glue or some other type of glue to seal the piece into place. You want a hammer on hand to smack the fittings tight before whatever glue sets.
Then do the same to the side hole but use the 90 degree fitting on the bottom. The best orientation I have found for it puts the fitting at a 90 degree angle from the inlet to outer edge, though anywhere from 75 to 90 degrees would probably work fine.
Cut a PVC piece between 4 and 6 inches (they both worked equally well so I would go with 5). And install it on the center bottom.
What transition pieces you need for the top will depend on your particular shop vac hose size. The outlet of mine fit by nature of the inner ring on the PVC straight connector. However, the inlet needed a section of PVC sanded down to almost nothing to fit my shop vac hose.
Quick notes and questions:
The center pipe goes to the shop vac and the outer goes to your suck-it-up hose or ducting to tools.
My hose can reach pretty much all areas of my tiny shop, so I am using a shop vac that attaches to the wall above the collector. However, if you needed yours to roll around, a stable cart to put the vac and the collector on together would be a good idea.
Could you use a 5 gallon bucket instead of the 3.5?
Yes. However, the suction would be more likely to cause bucket collapse. The shorter 3.5 has better structural integrity.
Could you use a solid color bucket instead of the transparent?
Of course... but who doesn't want to see that sawdust go spinning around like a tornado? Also, it makes seeing if anything is getting stuck on your slot edges or if the container has gotten too full obvious at a glance.
When do I need to empty the collection container?
I have not even come close to needing to empty mine since I am only a hobby wood-worker. I have read reports online that similar systems only need emptied when completely full and starting to fill into the top Semi-Thein-Clone bucket. However, I would really recommend emptying the collection when it is no more than 3/4 full. Letting it completely fill and then start sucking into your shop vacuum would clog your filter and defeat the purpose of the collector.
Would I sell this item pre-made for you?
No. It is simple enough to build and if you really would rather throw money at it instead, you could check out the Dust Deputy (but you will need the kit, not the DIY version or you still have to build stuff).
Thanks for reading and hope this helps someone make an easy dust collector.