I tried to laser cut hubs to fit the props to motor shafts as described in the assembly notes, but was not happy with the results. So I used some 5/16 alum. shaft and drilled a #32 hole (0.116 inch) hole thru the center of the shaft. I put the shaft in the lathe so it was easy to find the center of the shaft. I used a center drill to start the hole. I made the shafts 1.125 inches long and later cut them down to the width of the props. The props from HobbyKing were #OR001-01503/4847 replacement fan for 3inch/76.2mm EDF (7blade) and had a 5/16 dia. mounting hole. The motor shafts are around 0.1155 inches. So you need a hub to lock the two pieces together. I used a vise to push the alum. shaft into the prop hole and made it flush. I drilled a hole in the side of the prop and through the alum. hub, I just made, for a 4-40 set screw. I tapped the hole and finished the hole with a bottom tap. The screw is to lock the prop/hub to the motor shaft. I drilled the threaded hole to line up with the motor shaft hole.
I made add a hole in the prop guards to make it easier to get the props on/off the motor shafts. You have to angle a screw driver to get to the set screw.1974-propandhub.jpg (143 KB) 1975-propandtaps.jpg (148 KB)