By Martin Harris.

Dust Deputy vs Thien Baffle

A cyclone like the Super Dust Deputy holds back more fine dust. A Thien baffle costs less and takes up less height. In the numbers on my best dust separator page, the Super Dust Deputy caught 98.0% of fine dust and a DIY Thien baffle caught 94.5%, at close to the same airflow: 410 CFM for the cyclone and 395 CFM for the baffle.

If protecting your filter and your lungs comes first, the cyclone earns its price. If money or ceiling height is tight and your work makes mostly chips, the baffle is a strong build. Below I compare the two on fine dust, cost, space, airflow, and build effort, for collector setups and for shop vacs.

Side by side

Cost, capture, airflow, and static pressure figures come from my best dust separator page. Dimensions and HP rating: Oneida Air Systems. Scaling: Phil Thien, jpthien.com, and Hector's Thien separator design sheet on woodgears.ca.

How each one separates dust

Both use spinning air, in different shapes. A cyclone is a cone. Air enters along the wall at the top and spirals down inside the cone. The spin throws dust against the wall, where it slides down and out the bottom into the bin. The cleaner air turns and leaves up through the center. The spin puts steady force on the small, light particles, which is the fraction that is hardest to pull out of the air.

A Thien baffle is flat. Air spins in a short space between the lid and a disc, and dust drops through a 240 degree slot along the wall into the can below. Phil Thien shaped the disc to keep the spinning air away from the dust already in the can, so it doesn't get picked back up and carried to the filter. My guide on how to build a Thien baffle has his dimensions and a full materials list.

Speed of spin matters for both. Matthias Wandel wrote on woodgears.ca, after building his own separator, that slower circulation means less force on the dust and weaker separation. That is also why both types need an airtight lid: a leak lets air in that never joins the spin.

Fine dust separation

Fine dust means the tiny particles that float in the air and settle slowly. Sanding makes a lot of it. It is the part that clogs filters, and it is the part that matters most for your lungs.

The gap in the table, 98.0% against 94.5%, is dust that goes on to your filter. A separator and a filter do different jobs. The separator removes bulk dust so the filter stays clean longer. The filter decides what ends up in the air you breathe. More dust reaching the filter means more frequent cleaning and faster loss of airflow between cleanings. My guide to the best dust collector filters covers that second job.

Phil Thien wrote that his baffle approaches true cyclones in separation efficiency, and the numbers agree: close, with the cyclone ahead. On the shop vac side, The Wood Whisperer's cyclone separator shootout compared the Oneida Dust Deputy Deluxe with the ClearVue Mini CV06 and the Rockler Dust Right Vortex. He rated the Dust Deputy the overall winner, and the other two lost on fine dust getting through to the vac.

Cost

The Super Dust Deputy runs about $265 at street price on my separator page. The Thien baffle build comes in around $60 in materials. Both need a container. Oneida's Deluxe kits include a drum, and its DIY kits leave the container to you. A baffle build uses whatever can or drum you choose, so a good steel can you already own brings the cost down further.

On a shop vac, the pattern holds. A Dust Deputy costs more than a plywood baffle lid, and both need a bucket thick enough to hold its shape. Oneida says a 5 gallon bucket needs at least a 90 mil wall (0.09 in.) under shop vac suction.

Space and height

Height is where the baffle wins in a garage. The Super Dust Deputy 4/5 cyclone body is 23 in. tall on its own. Oneida lists the Deluxe kit at 43-5/8 in. tall with its 15 gallon drum, with the inlet centered at 39-3/16 in. That has to fit under a bench, a shelf, or a garage door track, with room to lift the cyclone off when you empty the drum.

A Thien baffle hangs inside the can, so the only added height is the lid and the fittings on top. The tradeoff is that the baffle uses the top few inches of the can. In Thien's shop vac build the baffle sits about 3 in. below the rim, and he says you can fill the can right up to the bottom of the baffle without hurting separation. He also found that the plain cyclone lids he tested got worse once the can was about a quarter full.

Floor space is close to a tie. Both sit on top of a container, so the footprint is mostly the drum or can you pick.

Airflow cost

Every separator adds resistance, and resistance costs airflow at the tool. Resistance is measured as static pressure, in inches of water column (in. w.c.). On my separator page the two read close: 5.2 in. w.c. for the Super Dust Deputy and 4.8 in. w.c. for the Thien baffle. That difference is about what 1.5 ft of 4 in. flex hose costs, based on Oneida's published loss of .280 in. w.c. per foot of 4 in. flex.

Oneida's static pressure guidance suggests budgeting roughly 2 in. w.c. for a cyclone as a starting point, and notes that the real drop depends on the model and the airflow. The data behind my Harbor Freight review shows about the same for a baffle: roughly 2 in. w.c. of added system loss on a 2 HP collector with a Thien baffle mod.

Pick either one and plan your duct for that extra loss. A small collector has less pressure to spare, so keep runs short and flex hose to a minimum. My guide to dust collector static pressure explains how to add up losses across a whole system.

Build effort

The Super Dust Deputy bolts to a lid with the included gasket and hardware. The 4/5 Deluxe kit comes with a pre-cut drum lid and a lid clamp, so setup is mostly connecting hoses.

The Thien baffle takes an afternoon. You measure the can, cut a lid disc and a baffle, lay out a 120 degree solid section and a 240 degree slot, mount the ports, hang the baffle on spacers, and seal everything airtight. None of the steps are hard. The result depends on how carefully you seal it, since a leaky lid pulls in outside air that skips the spin.

Which one fits your shop

• Buy the Super Dust Deputy if you sand a lot, run a cartridge filter you want to keep clean, or someone in the house has breathing problems. The higher fine dust capture is worth the money there.
• Build a Thien baffle if the budget is tight, your ceiling or bench height is low, or your work is mostly sawing and planing that makes chips.
• On a shop vac, the same logic holds at a smaller size: a Dust Deputy for more fine dust capture, a baffle lid for the cheapest build. My Dust Deputy vs Super Dust Deputy guide explains which cyclone size matches a vac or a collector.
• Either way, keep the lid sealed and empty the bin before it gets too full.

For every separator I recommend, see my best dust separator roundup. For where a separator sits in the full system, start with my complete guide to small shop dust collection.

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