Hi,
After reading thro the various post decide to build a seperator. System is 100 mm plastic duct. The seperator is outside and Vac in a lean to on the shed.
Woks very well, I tried the test with chalk dust mentioned in one of the post. Was colored blue. Which was found both in the seperator and on the filter in the vac. Would seem that only really fine dust gets past the seperator.
Have attached some pictures
Nice job! My next one will be a 5" with fectangle inlet for my delta 750-60