Dangers of connecting Neutral to case of blower?
The fact of the matter is that 99.9% of all electric clothes dryers and electric cook stoves in USA operated under these very conditions from the time of the WWII until the very late 20th century. At that point America was ready for another layer of safety.  Does the 4th wire make it safer? YES. As long as the neutral wire never comes loose from the neutral bus bar and all other connections remain clean, tight and dry you are relatively safe. Would I do this in my own shop? Probably.  Would I do it around children or family conditions? NEVER!