Slowly, not suitable for long duration, no replacement stones with other grains

Neutral:
° price

Disadvantages:
- Too slow, thereby uneven wear of the grindstone
- Not suitable for long missions (max. 10 min, and who can grind more than a knife properly, cooling-down must appeal again and again)
- There is no substitute stones with finer grits and the available grain is for kitchen knife / cutlery too coarse
- Grindstone wobbles considerably

Conclusion: For offer this price there are much more professional devices, which are used more flexibly.