The permanent magnet ring is 5 mm high and (as AdaSch observed) the shaft length does not allow this ring to match the height of the stator. This assures that the thrust bearing will feel thrust from the shaft. The motor was clearly designed for this. The end of the shaft is spherically polished and greased.
AdaSch's idea to simply eliminate the thrust bearing makes some sense after examining and measuring the motor. The distance from the center of the metal plates to the circuit board is 2.5 mm. Therefore if magnetic levitation takes place and keeps the rotor exactly centered heightwise on the stator the rotor will just graze the circuitboard. ... So AdaSch's modification amounts to replacing Toshiba's shaft end thrust bearing with the circuit board as thrust bearing. The modification might reduce the net axial thrust, but it will be born by an unlubricated plastic-to-plastic contact. This might be quiet. It might cause trouble later, as some have reported. It is a dicey cute solution.
Great post (nice photo's too). It's rather interesting some people perform the mod and it works great, some such as myself, hear more
noise. After doing the mod and seeing the results I came to the same conclusion as you, i.e. the thrust bearing is supposed
to be there. This leads me to conclude what is really needed is, oil for the bearings.
Also, I've wondered if the 'cage' surrounding the fan can be easily removed or if doing so will break the the little metal tabs holding it to the copper plate? Your pictures show these disassembled. Do you know?
If the cage can be removed and easily replaced, I think the way to go is to remove the cage, remove the fan (pull up gently, may want to use bent paperclips hooked close to the hub then gently
pull - don't want to break the fan) then OIL using a good light weight motor oil (SAE 5 or 10) mixed with graphite powder. Apply oil solution into the bronze bearing hole and to the axil. This oil/graphite solution is a very good lubricant and a long lasting solution. If you can get a couple of drops into the bronze bearing to create an oil-bath for the axil/thrust bearing, the better (that would be my
BTW, I've also used the oil/graphite solution to re-lub expensive
irreplaceable cooling fans on expensive
computerized machine tools ... works great! For those in the USA, your local Walmart should carry tubes of graphite powder.