Building a Thien Baffle for Dust Collection & Chip Separation

Building a Thien Baffle

A Thien baffle separates chips, preventing them from hitting the dust collection impeller and also collects a lot of dust, keeping your filter clean and maintaining air flow.

I researched both a Thien baffle and a cyclone before deciding on the Thien.

I started with a basic plan in Sketchup. I knew the size of the trash can I was using. I wanted to match that width as close as I could since this is going in a corner.
The interior of the baffle has a slot for sawdust to drop into the trash can, while the impeller is mounted on top of the baffle to reduce bends in the line.

Purchase List:

(1) 4'x8' sheet of plywood
(4) 6" lengths of 5/16" threaded rod
(16) 5/16" fender washers
(16) 5/16" nuts
6"x38" vinyl, plastic or other flexible panel. I used an LVT tile
(1) trash can
caulk to seal joints, gaps, etc.
Total Cost: $120

Tool List:

• table saw
• router
• jig saw/band saw
• drill 
• 5/16" drill bit
• 1/4" router cutting bit
• 1/8" router cutting bit
• router cutting jig (my how to)

Cut List:

(2) 18"x19" blanks for the top and bottom
(1) 4.75"x2"
(1) 4.75"x5.75"
(1) 4.75"x9.25"
(1) 37" long x 6" hardboard panel for the sides

Introduction
With adding dust collection, I wanted to maximize efficiency. The Thien Baffle protects the impeller from being hit by wood chips and also collects a lot of dust, keeping the filter clean. The cleaner the filter, the better the air flow.

I considered making a cyclone style filter but I couldn't find anything confirming the effectiveness.
The Thien baffle's use is widespread, and it also allows the trash can to get rather full before pulling the excess into the filter.

I created a few iterations in Sketchup before finalizing a design.

Procedure
I started with a galvanized trash can, this dictates the size of the baffle. This trash can has a 17" inner clear diameter. I chose this trash can as I'm putting my dust collection in a corner, and I have to maintain a certain width.

While you can buy trash can tops that mimic the design and some designs have the baffle completely inside the trash can, I wanted the PVC pipe to run straight into the baffle with no 90* turns.

The baffle will sit on top of the trash can with a plywood lip to ensure good fitment.

I rough cut 18"x19" blanks for the top and bottom of the baffle. Both have a 2"x5.75"x10" extension for the pipe inlet. I made the rough cuts a bit wider than necessary to leave room for the router to trim.

The top has a 5" hole for the dust collector motor. The motor will feed directly into the filter bag.

The interior bottom of the baffle has a 240* 1.5" wide slot. Both top and bottom have a 1/8" wide x 1/4" channel for the rubber sides.
That channel runs right into the bottom slot. You don't want a ledge for dust to sit/collect.

The circle cutting jig (check out the how to) made cutting the curves very easy while ensuring the top and bottom were exactly the same size.

I cut each slot with two passes as trying to cut through .75" in one pass was too much strain on the router. The jig ensures each pass is aligned.

A 4.25" diameter hole was cut out of the 4.75"x5.75" cut. This is for the inlet.

While I used (4) threaded rods to space the top and bottom, doing this again I might have just used wood posts around the perimeter.
I was reusing rods, so I had to re-thread them to clean them.

The top and bottom are sandwiched with washers and nuts.
I sketched up a few iterations and while the first few didn't have space around the perimeter, the final version did as I needed a ledge for the baffle to sit on a trash can.
The LVT floor plank sides are 6" deep along the slot, but 5.25" everywhere else. A quarter of an inch is inside the channel on the top and bottom plate. I didn't want to create any kind of ledge to catch dust so the sides extend the depth of the slot. Originally I was going to use hardboard, but it just doesn't flex enough to fit the diameter. It snapped trying to fit it to a 17" diameter.

A ring with a 17" outer diameter was glued to the bottom. It's 1" wide and the face is flush with the slot. This ring helps mount the baffle to the trash can.

I glued the inlet together and to the bottom first. I glued it to the top at the same time I caulked the channels for the side and tightened the nuts down for a tight fit.

I measured the nut/washer height to exactly 4.75". I tightened the bottom nuts down and then prepped to caulk the sidewall in place on the top and bottom. I wanted to be sure it was air tight. With the sides being in a channel, caulk fills any potential air gaps.

I added weather stripping to the trash can. I want a air tight fit between the baffle and can.

I added a tab on one of the back corners to prevent the baffle from wanting to turn. The bottom plate needed to be about an inch wider to sit on the trash can properly.

 

I considered attaching springs from my scrap to hold the baffle to the trash can, hooking to the can's handles and drilling a hole into the bottom plate. With the motor mounted to the wall and the way my trash can is mounted, I didn't need the springs. The trash can sits on a plywood sheet bolted to a scissor jack. The scissor jack lifts the trash can tight against the baffle which is hung from the motor. The motor is mounted to the wall. Lowering the scissor jack lowers the trash can and allows for removal.

Conclusion
A chip separator of any sort is mandatory for a dust collection system. It protects your impeller and filter. While there are certainly expensive out of the box separators, this is much more affordable and a quick project. Plus I like making stuff.
I painted the outside white to match the PVC pipe and the walls.