Before I get too far into this I want to state that I am still in the begging stages of testing this and it is by no means complete. I was actually hoping for some input ideas as my testing of it progresses. I took the idea listed here: http://www.jpthien.com/cy.htm and scaled it down to fit 1.25" hoses because that is what I have on my shopvac and on the hose to my CNC. Also I will include the exact parts I used instead of general names. I spent about 2.5 hours walking around the hardware store looking, comparing, measuring and testing before I settled on the part for my build.
I plan on trying several types of cyclone fixtures on the base of the lid, but I saw the funnel in the picture as I was leaving and it was .69 so I figured that I would give it a shot before cutting and building a base plate out of wood as the other DIY cyclone does. The design idea is that the material entering the bucket will be forced in a circle towards the bucket edge, then gravity will pull the debris down while the funnel lid will re-direct all fine dust back into the cyclone stream acting as a barrier to exiting into the shop vac. Also the funnel serves the purpose of preventing turbulence from upsetting settled dust in the basin.
My goal here is to be able to run my machine for an entire job without a loss in performance from my shopvac. As it stands right now I take it apart and clean out the filter at every tool change or about hourly for most jobs and the bin is only about 1/3 full at most. It just plugs up the filter and as I get closer to a filter cleaning, more dust starts flying around the room.
Here is the parts list:
1 x Elbow 90 degree 1.25 FPT $1.99
4 x 1.25" Rubber Gasket $.99 Each (found in the sink plumbing section)
1 x Bushing 1.5 to 1.25 40PVC FPT $2.99
2 x Male adapter 1.25" x 1" $1.39 Each ( Street, threaded on the male end)
1 x 5 gal bucket and lid (I had one in the garage)
1 x Large 8" funnel $.69
Total - bucket: $13.40


