To sharpen the blades of the tools.
There are also the diamond stones, but I wouldn't recommend that, they're more proper for harsh tools, the bonsai tools are more delicate. A320 is recommended for blunt tools. Use a 1200 to refine the edges. The 4000 is for polishing. Pay attention to your tools' material to choose the proper sharpening stone. For cheaper materials, use the 1500. Summing up: 300-800 to move a lot of material, 800-2000 to refining, 2000-6000 to polishing (this for whetstones, diamond stones are harsher, remember that). Put the wheatstone on the water until al the bubbles come out. When sharpening, concentrate on the angled side. On the flat side you're only taking the burr off that you'll create.
I'm Josh - creator of the Bonsai-En YouTube Channel and Podcast, and on this list, I share with you my recommendations of all the essential tools to get started with bonsai.
I've categorized the items in Pruning, Modelling, Root Care, Repotting, and Cleaning. And I've also rated them based on the value for money and whether or not the item is essential to get started.
You can see the full video review of items here, or specific snippets within the list: https://www.youtube.com/watch?v=w6Z0s4ay5-g&t=74s
If you are just getting started with Bonsai, or are an enthusiast of this art, join us at the Bonsai En podcast and follow our YouTube channel for tips and updates.
You can also visit our Website www.Bonsai-En.com.au or our Online Bonsai Shop www.Bonsai-En.Shop or follow the links below.