Toolinsane,

I agree with Moby Duck in all points. I did try to design a dual Thein/cyclone system for a Jewelers blast cabinet. Basically placed a small Thein on top of the cyclone and came in at right angle with the low pressure side and the intake from the blast cabinet. The proto worked and made from acrylic but the design parameters were toooo constrictive as in using a 12VDC fan. With higher SP/DP (Static/Differential pressure) I could get particles down to 3-5 micron (typical for these type cabinets) separate them and manage dust with 1 micron filters on the fan to keep it out of the room. Basically one needs to have sufficient HP/SP/DP to achieve these kind of results and 12VDC fans don't have a lot of SP. The abrasives for these cabinets can be toxic, let alone the dust side of it so getting everything one can is important. Commercial systems with recovery/filter for Jewelers are incredibly expensive and now know why...however my system would work if I could find something off the shelf and overcome the 12VDC - HP/DP/SP issue. CFM is important but only as related to SP/DP and available HP.

The Thein for mine was ~4" and attached to a 3" translucent plastic jar with a conical funnel (Had to experiment with size and length) inside. The jar could be detached from the lid the Thein was attached to, to be emptied or recycled. Basically could see the additional speed of the vortex as particulates passed through the system.

You didn't specify if your HFT cabinet was a bench or free standing 40lb unit? Each will require its own design based on volume, Pressure, nozzle type and size. If your vacuum cleaner has enough HP/DP/SP for the cabinet size it should work with the right design. Two other things: First pick up a Flow meter, they are a lot cheaper now (Amazon) it's decent for this kind of work. Second is that it takes 7 Diameters to get straight air from the low pressure side (Vacuum side) which is preferred.

Had 12 years in Airflow Management & Control...Here are some links that may help.

Dust Collection Research - Dust Collection Basics
https://www.dwyer-inst.com/primer.cfm
J. Phil Thien's Cyclone Separator Lid w/ the Thien Cyclone Separator Baffle
This is about Jewelry but informative for design
http://azglassclasses.com/portal/com...rving-nozzles/

Hope this helps. Good Luck with your project.

PJ