With my increasing interest in woodworking and the amount of dust created in the process I needed to find a solution for collecting the dust created in my garage without clogging up the filter of my shop vac. There are plenty of solutions posted in the web which vary from buying and assembling commercially available dust separator systems to making your own. Here I am presenting the solution I came up with, that is as usual based on all the good stuff I could find on the web and then some of my own ideas. I went for the simplest possible design which turned out to be able to handle a wide range of machines and dust/shaving volumes with 'Version2'.

In a nutshell, I: (i) Avoided the cone shapes design most separators use and used a simpler design. (ii) Used for the first version a small collection container, i.e. a standard bucket, which worked well for small dust volumes created by a table saw or a miter saw. This version wasn't that great for large volumes though as the bucket filled up way to quickly. (iii) Switched for the second version to a large collection container, i.e. a 55 gallon drum, which worked well for larger shaving volumes created by a router or a planer as well as for small dust volumes.

Credits: The main inspiration, design ideas and grasp of concept came from many weblocations such as this, this, this, this, or this one.

Specifically this instructable by Steliart - Stelios LA Stavrinides sparked my interest in building a low cost separator by using buckets. Once I dug a little deeper, I found this instructable by TabLeft which opened my eyes to the fact that I might be able to build a much simpler vortex type dust separator without actually using a cone. I even found a video, that proved the concept of the design I was going after.

And here you can see what I did.

Step 1: Materials & Tools

Materials:

List of materials and tools used for this build. I am giving home depot links as an example source of materials, but other hardware stores such as ACE or Lowes carry the items as well.

Version "tiny": 2 buckets with lids
Version "BIG": 2 buckets with lids & 55 gallon drum (craigslist $20)
Less than 2 feet of 2" PVC piping
PVC DWV 90 Degree Hub x Hub 2" Elbow
3x PVC DWV Hub x Hub 2" Coupling
1x DWV Flexible PVC 2"x2" Coupling
PVC cement
silicone based caulk
shop vacuum with 2 hoses ( I have this one)
some scrap wood
HVAC tape or other air tight tape that sticks well

Tools:

Sharpie or other marker
Carpet Knife
jig saw
reciprocating saw
hole saw
cordless drill & drill bits
screwdriver
caulk gun

Step 2: Interface Dust Collection/Dust Separator Bucket

We start with the interface between dust collection and dust separator buckets. The pictures of the building process are pretty much talking for themselves. I'll try to keep my explanations fairly brief:

With the carpet knife cut out the bottom of bucket #1.
Center the bottom of the bucket on a bucket lid and mark its circumference.
Just inside the markings, cut a hole into the lid with the carpet knife. The ideal hole size allows the bottom part of a bucket to sink ~1/2" into the hole.
Place the bucket lid with the hole on the bucket #2.
Stick bucket #1 into the hole.
Find a piece of wood that fits between bucket and the lip of the lid.
Cut the piece into eight 1.5" x 2.5" pieces.
Select a screw of the same length than the wood thickness.
Determine the core diameter of the screw.
Select a drill with slightly lower diameter.
Drill 2 holes into each wood piece.
Stand the bucket on a table, place one spare wood piece flat on the ground, stand another on top of it, and slide it against the bucket.
Drill through one of the holes and fasten a screw from the inside.
Repeat with the second hole.
Evenly space out the remaining wood pieces around the bucket and repeat the fastening process.
Turn the bucket upside down and place the lid with the hole onto it. If necessary, cut away plastic that prevents a good fit.
Fasten the lid with screws on the 8 wood sections, by drilling pilot holes again before fastening the screws.
Seal the crack between bucket and lid with HVAC tape.

Step 3: Reinforcing & Preparing the Top of the Dust Separation Bucket

In this step we are completing the top of the dust separation bucket, i.e. the top bucket. The idea is to reinforce the top to give it enough stability to hold up the weight of the PVC tubes and the vacuum hoses. The thickness of the wood I had around was about 3 mm (1/8"), so I build my top out of 2 pieces of wood. One that fit inside the rim of the top and one that sat on top of it.

Place the top of the bucket on a piece of wood.
Mark around it with a pen.
Cut it out with a jig saw or other saw.
Mark another piece of wood from the inside of the bucket.
Cut it out with a jig saw or other saw.
Select screws that fit to the thickness of both wood pieces combined.
Select drill according to screws.
Place smaller wood disk in top of bucket top.
Place and align larger wood disk on top.
Turn everything around.
Drill a few pilot holes into top & wood and fasten them to each other.
Determine center of assembly.
Drill hole with 2 1/2" hole saw through wood. Stop when you reach bucket top.
At the same location, cut a hole of the same size into bucket top using the carpet knife.
Measure distance from outside of lid/bucket to inside of lid/bucket. This was 1 cm in my case.
Add 5 mm and mark the distance from the outside of the wood disk.
Drill a second hole with the 2 1/2" hole saw so that that outside of the hole is on the mark.
At the same location, cut a hole of same size into bucket top using the carpet knife.

Step 4: Complete the Dust Separator Top With PVC Tubing

In this step we are mounting the PVC pipes onto the top of the dust separator bucket. Note this 2" piping has an inner diameter of 2".

Measure the depth of the protruding part of the 90 degree bend, for example d = 2 cm.
Measure the thickness of your wood/lid top assembly, for example t = 1 cm.
Cut a piece of 2" PVC pipe with the length l = (2 x d) + (1 x t) - 0.5 cm = 4.5 cm using the reciprocating saw.
Use a knife to deburr the edges of the pipe inside and outside.
Put PVC cement on the inside of the 90 degree bend and the outside end of the pipe.
Quickly press the pipe into the bend.
Let it dry according to the instructions for the glue.
Stick the short tubing piece through the hole at the outside of the top.
Glue the tube to a second bend, arranging the bends as shown in the pictures so that:
1. the bend that will end up inside the bucket would blow air in a circle around the bucket.
2. the bend that will end up on top of the bucket will point away from the center of the bucket.
Cut another 4.5 cm, two 6 cm, and one 25cm piece of 2" pipe and deburr them.
Glue the 25 cm piece to the coupling and let it dry.
Glue the 4.5 cm piece to the other side of the coupling and let it dry.
Stick the short pipe end through the center hole from the inside of the top/bucket to the outside.
Glue the third bend onto the pipe and let it dry. Note that I used an extra coupling and pipe length in my pictures. These are not necessary. You can go straight to the bend. Also make sure you are pointing the bend in a direction that is convenient for placing your shop vac. I used a 90 degree angle between bends.
Glue a 6 cm piece of 2" pipe to each of the bends. These are for the hose attachments.
Last not least, put some beads of silicone around the pipes at both the outside and the inside of the bucket. Let them dry overnight.

Step 5: Hose Assembly

In this step we finalize the small version of the dust collector.

I bought a new/second vacuum hose for this separator. It came with three hose termination options. Attach the smooth termination option to the hose.
Attach one flexible 2" coupling to the hose and the PVC pipe that comes out of the center pipe / outlet of the dust separator. This hose attaches to the shop vac inlet.
Attach the second flexible 2" coupling to the hose and the PVC pipe that comes out of the other pipe / inlet of the dust separator. This hose attaches to your saw, router, planer, whatever. In the picture this hose is the new shiny black one.

Step 6: Test of "tiny" Version

It works.

For once, clean up your workshop and sweep up a pile.
Turn on the vacuum and suck the dirt through your assembled dust separator to the vacuum.
Once the pile is gone. Check where it went.
In my case it ended up in the lower "dust collection" bucket and nothing in the shop vacuum. Yeah.

However, I realized quickly that the "tiny" Version is great for the table saw and the miter saw. But for the router and the planer the volume in the bucket was too small. So I moved on to the "BIG" version.

Step 7: Upgrading to the "BIG" Version

To upgrade you need (i) another bucket (or use the dust collection bucket of the "tiny" version), (ii) a 55 gallon drum that has plastic top (craigslist), (iii) silicone glue.

Mark the bucket 1 -2 " below the widest rim.
Cut the bucket along the marking.
Take the cut off top part and center it on the drum's top.
Mark the circumference.
Cut a hole at the inside of the marking.
Fit the bucket into the hole. Carefully shave more material off until the bucket top fits tightly.
Put silicone beads on the inside and the outside of the bucket/drum top connection and let dry overnight.
Done. Woodwork away.

Note that since I finished this separator I have routed, planed, cut, ripped, cleaned and sanded for hours. The drum still isn't full, but the shop vac is still empty. The "BIG" device is maybe a little spacious but otherwise an awesome addition to my shop. Pick your own size and let me know when you build one.

Step 8: Update Step: Adding Wheels

After some time of successfully using the drum as a dust separator I followed some friendly advice and added wheels to the setup. Though the drum never really got as heavy as I thought it would, the wheels sure make it much easier to move the setup around.

Materials & Tools:

4 casters: $3.49 (on sale), Harbor Freight. Note that the brakes of these casters have a poor design. From 12 casters, a total of 4 had dysfunctional brakes. Otherwise the casters were fine.

Screws: #12 x 3/4, Home Depot or Lowes

Washers for #12 screws, Home Depot or Lowes

Wood screws: 2" long, Home Depot or Lowes

Plywood: 600 mm x 600 mm, 3/4" thickness, Home Depot or Lowes

Leftover wood pieces, e.g. 2x4 pieces

Saw

Drill

Drill bits

Step-by-Step:

Measure the diameter of your drum. Mine was just smaller than 600 mm.
Cut plywood to size using any available saw appropriate for the job.
Sand the edges.
Place casters on corners and mark hole locations for screws.
Determine core diameter of screw and select drill bit of slightly smaller size.
Drill 16x pilot holes.
Fasten casters with 4x screws and washers.
Turn setup around and place drum on it. Note: You could stop here. The drum was stable and not slipping, but I did a few more steps to prevent the drum from sliding.
Cut four pieces of wood to a length of about 6".
Sand the edges.
Lay one piece next to the foot of the drum and mark the size of the lip on the board. Width and height of the lip of my drum were 7 mm and 10 mm respectively.
Set your table saw (or router) to the same height, i.e. 10 mm.
Remove the measured amount of material from the edge of your wood pieces, i.e. 7 mm x 10 mm.
Place the wood pieces (i) with the groove down, and (ii) the groove toward the drum on the four corners of the plywood.
Slide the wood over the groove and fasten it with the wood screws. Drill pilot holes as needed.
Ensure that the drum is safely secured to the plywood.
Done.

Now if you feel brave, put on a helmet, hold on to your drum, jump on the plywood and roll down a hill... all on your own volition and responsibility of course. If you don't feel brave, you may now go crazy with your vacuum in your shop and clean up for once. In any case, enjoy the setup.