Sure, there are prebuilt dust separators out there; like the Dust Deputy, the Dustopper, and many, many knock-offs. And many are reasonably priced. But, where is the fun in that? With just two 5-gallon buckets, 2-inch PVC pipe and connectors, and scrap plywood, you can make your own.
Home-made dust separators often suffer from the same deficiency. Dust makes it through the separator proportional to the dust collected by the separator. As dust fills the container, the airflow agitates the settled dust as it is in nearer proximity. While the separator may operate at 99% efficiency when empty, as it fills, efficiency may drop to 70% or lower.
This project solves this problem with the addition of a baffle (which has been done many times before), along with an extended outflow pipe with many smaller holes drilled in its side to disperse the outflow pressure. As you will see, this allows for high efficiency, even when near-full.
We will modify one 5-gallon bucket with all the dust-separating functionality. All of the work below concerns this separator bucket. A second 5-gallon bucket will collect the sawdust. This collector bucket is unmodified.
Prepare the Separator Bucket
Trim the first inch off the top of the separator bucket using a utility knife. Ensure that about 1/2-inch remains between the cut and the first lip on the bucket. Then, using the utility knife, chamfer the outside of the new edge to facilitate mating up with the collector bucket. Once complete, you should be able to seat the separator bucket inside the collector bucket with a friction fit.
Drill out a hole – large enough to receive one end of a 2-inch 90-degree elbow PVC connector. Use a 2-3/8 inch hole saw and file it to a perfect fit.
Baffle & Outflow Support
Next, we need 2 plywood circles: one to seat at the bottom of the separator bucket (outflow support), and one to seat at the open end (baffle). Trace the top and bottom of the separator bucket onto the plywood and use a jigsaw to cut out the outflow support and baffle. I used a hastily made circle-cutting jig on my table saw to refine their sizes. If you do not have access to a table saw, hand file to fit with a half-round hand file. The baffle should fit precisely. The outflow support has greater tolerances.
Note: do not trust the traced top of the bucket to be a circle. Because you are tracing the outside circumference of the bucket and reducing it to match the inside circumference, you have room to correct any error. After finding the center of the baffle circle, use a compass to make a true circle.
Once sized correctly, the outflow support should seat entirely against the inside-bottom surface of the separator bucket, and the baffle should seat inside the mouth of the separator bucket. Double-check that the separator bucket still seats inside the collector bucket with the baffle in place. If it does not, continue to size-down the baffle.
With the outflow support seated in the bottom of the separator bucket, cut out a hole that matches the hole in the bottom of the bucket. Test the hole to ensure it will receive the PVC elbow connector. Refine the hole (as necessary) with a half-round hand file. Because the hole in the bottom of the bucket may not be perfectly centered, it may be useful to add an alignment mark on the outflow support and the bucket for future reference.
Next, draw 3 radii from the center of the baffle with 120-degree separation. Use a jigsaw to cut out 3 sections from the perimeter of the baffle, about 2 inches deep. Leave 2 inch wide feet at the full width where we marked the 3 radii. Glue a scrap of plywood on the inside face of each of the feet to double the surface contact with the inside of the bucket. This will give us the needed area to attach the toggle clamps. Attach the PVC plug to the inside-center of the baffle with a screw and seat the PVC coupling on the plug.
Cut a length of PVC pipe to length so that it fits between the dry-fit PVC elbow connector and PVC plug. This is our outflow pipe. Drill holes evenly distributed along the pipe, starting about 3 inches below the PVC elbow connector to 1 inch from the PVC plug. The area of the drilled holes should exceed the area of a cross-section of the pipe. If you are drilling 1/2-inch holes, 32 holes are recommended. This will double the cross-section area of the pipe, and halve the negative pressure of the outflow.
Next, we will construct the inflow box that attaches to the separator bucket. Build a box from plywood that accommodates the full cross-section of the PVC pipe. This box should have an inside width of at least 2-3/8 inches and a length of about 6 inches. Trim the box to match the side curve of the separator bucket. It is easier to mark the curves on the box sides before assembly. Cap the square end of the box with a piece of plywood. Cut a hole (with a diameter of the pipe width) in the plywood cap. Push a section of pipe through the box and trim the pipe to match the curve on the inflow box. Attach the box in place on the separator bucket with screws (but no adhesive). Shine a light through the pipe and trace the lit-up section on the inside of the bucket. Remove the inflow box. Cut out the traced section from the separator bucket.
All we have left is to put all the parts together. Attach the inflow box first with screws. Caulk as appropriate to create an airtight seal. Next attach the small plywood circle on the inside of the separator bucket, being careful to align the outflow holes. Caulk between the plywood circle and the bucket at the hole, and attach with screws from the outside. Place the PVC elbow connector in the outflow hole from the outside. Dry-fit the outflow pipe in the PVC elbow connector. Install the plywood baffle at the separator bucket opening. Optionally, install small toggle clamps on the outside of the bucket where each of the baffle feet meet. Otherwise, add screws from the outside of the separator bucket to secure the baffle. Place the assembled separator bucket onto the collector bucket, and set the toggle clamps to secure the connection.