This is a remix of SteveC's nice pinwheel (ThingID: 121959) - traced into SketchUp, cleaned up, made symmetric, and added a handle and bolt. The SketchUp file has been uploaded for anyone wanting to work with the design.

Required: print 1 each of the following pieces: pinwheel, bolt, and handle. Add a 626zz bearing.

Optional: instead of printing the handle, you could print the alternative_handle and add a 3/8" dowel for the handle

Printer settings: solid infill for strength and 0.3mm layers. Also printed successfully in 4 layers at 0.2mm.

1. Insert a 626zz bearing into the handle (add glue if needed - be careful to keep the bearing able to rotate).
2. Please note that there is a small lip protruding from the center hole on the pinwheel, and it is meant to be located on the backside of the pinwheel to reduce the amount of pinwheel contacting the bearing. Using a hair dryer on the high setting, heat the plastic of the pinwheel to make it easier to bend the 4 corners up and back onto the center (be careful not to overheat, especially with PLA). Bend it in such a way as to leave about an inch gap over the pinwheel's center hole and below the four corners being folded inward (this allows for more air to be caught into the fins).
3. Insert bolt into the four corners that have been bent to the center and finally through the center hole on the pinwheel. Then insert the shaft of the bolt into the bearing on the handle. It should be a snug fit but use glue if needed (again, please be careful when applying glue to make sure the bearing still functions).