This adapts the 5-inch intake on a Harbor Freight dust collector to allow it to accept a more standard 6-inch hose. It replaces the Y fitting on the impeller intake, using the factory bolt to lock it into place.
It's designed to be a tight fit. You'll need to work it into place carefully, and try to keep the bolt hole in the adapter aligned with the bolt hole in the impeller intake. It won't turn easily once you've pressed it on. I used a little paste wax to help get everything in place.
The Test Collars.stl are a couple of test pieces to ensure your scale is correct. The small ring has an inside-diameter which matches the ID of the small adapter end. That should fit snuggly on the dust collector. The large ring has an outside-diameter to match the OD of the large adapter end, for fitting in a 6-inch dust hose. I used them as a quick print to ensure sizing was OK.
Printed with 3 shells, 40% infill for strength. Not sure how the PLA will hold up, but it's not a very dynamic load. Don't crank down too hard with a hose clamp on the large end. The small end is well supported by the impeller intake.
Print settings on the Test Collars.stl shouldn't matter too much, as they're just to test sizing.