Since CNC jobs can run for quite some time and I don't want to listen to a vacuum for that whole time, I will be enclosing the vacuum in some sort of sound-deadening cabinet. I did not want to dedicate an expensive shop vac to my CNC table, all locked up in a sound-deadening cabinet so I purchased one of these cheapies;
My design is based on the Thien Baffle Separator, a variation of a cyclone separator that adds a baffle to reduce the possibility of reintroducing captured material back into the airflow that goes to the vacuum. I needed a smaller, cheaper version.
Let's start with the lid. With a hole saw, cut two holes just large enough to accept the PVC fittings. The first is spot on in the middle, this will be the straight fitting that will create a return duct to the vacuum. The second will be as close to the edge as possible and will accept the 45 degree fitting, this will connect to the vacuum hose that will be run to the CNC machine.
Fit the two 45 degree PVC fittings in an "S" formation through the outer hole. The "S" is an attempt to maintain as much velocity as possible with the solids, this is important. The inside fitting should be angled so that items coming out will be flung along the outside of the bucket in a spiral pattern creating our cyclone action.
Next, to create the body of our separator, cut the top off of one of the buckets just longer than the depth the lower 45 degree PVC fitting will hang down.