No, the drive motor is mounted on a flange that slides in a slotted fit to tension the belt while keeping the pulleys in alignment. I just spent a few minutes playing with the grinder and the eccentric is definitely for adjusting the depth of cut/size. The aluminum knob has a collar that can be twisted to zero it out that is graduated in 0.01mm increments in diameter, so turning by 1 increment would change diameter by about 0.0004". They're pretty widely spaced so easy to hit sizes in between. I stuck an indicator on the front of the grinding wheel collar, and it turns out the numbers on the spindle itself are increments of 0.1mm in diameter. So every full turn of the aluminum knob rotates and changes the increment on the spindle by 0.1mm in diameter, or actual movement of a little under .002". Pretty cool setup. Definitely a keeper.
The large red screw is a cap that covers another screw in the spindle which from what I can tell with Google translation of the manual is for adding/checking oil. There are two smaller flat-bottom screws that clamp the spindle cartridge eccentric rotation (not the actual rotating while grinding part attached to the wheel), one of which is visible lower than and to the right of the red cap screw.
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