I took apart my in-wall furnace and found that the fan blades are loose with the fan hub so when the motor starts or stops, the blades don't receive any torque and they make a lot of noise.
The pieces of the fan look kind of like this: http://airdrive.com/products/hubs/
I'm just trying to understand how I can mechanically or chemically attach the two pieces as I'm assuming they should be attached. I tried soldering and that obviously didn't work (didn't really expect it to either). Maybe there is some loctite glue I can use that will chemically bond them?
Here are some photos: http://imgur.com/a/pc5X9
Best Answer
These blades typically have a boss that has a set-screw and also might be "keyed" (i.e. has a round hole with a flat spot, to mate with a shaft equipped with a flat area, to provide a landing surface for the set-screw).
Your problem sometimes occurs when the set-screw has come loose due to vibration; check it and tighten if necessary. It is also possible that the boss in the fan blade/propeller was damaged by the spinning shaft, because the set-screw was loose; this normally requires fan blade replacement.