A 1000-grit whetstone can be sufficient for basic sharpening and maintenance of a katana. A 1000-grit stone falls into the medium grit range and can effectively remove minor nicks, restore the edge, and refine the bevel.

Using a 1000-grit whetstone allows for a good balance between speed and sharpening performance. It is suitable for regular maintenance and touch-ups to maintain the katana's edge sharpness. However, if the blade has significant damage, chips, or dullness, starting with a coarser grit stone may be necessary to address those issues first.

Keep in mind that the choice of whetstone grit depends on the condition of the blade and personal preference. If you desire a finer and more polished edge, you may consider using a higher grit stone, such as a 3000 or 6000 grit, after the 1000-grit stone to further refine the edge and achieve a smoother finish.

Ultimately, achieving the desired sharpness and edge quality depends on proper technique, patience, and consistency during the sharpening process. Experimenting with different grits and finding the right combination that suits your needs and the condition of your katana is key.