I just bought a 8" bench grinder from Harbor Freight to clean up some automotive parts with a wire wheel. On the left side of the grinder has a left hand threaded nut on it, while the other side has a right hand threaded nut. If I use two wrenches and try to tighten one side the other side will loosen. No matter how much I try this loosing/tightening thing keeps going back and forth. There is no special tool included and there doesn't seem to be a good place to hold the shaft in-place. Is there some special trick to get these wheels attached and secured?