The concave cutter, or Mataeda Hasami, is used to cut of whole branches of a bonsai tree. The slightly curved cutting area leaves a clean cut that will heal over itself nicely. This cutter is designed to prune entire branches and comes in a variety of sizes and quality classes. You can consider the concave cutter as one of the “heavy” tools in bonsai. You won’t need this bad boy during smaller pruning sessions.
When to use it?
Use it if you want to cut off bigger and/or entire branches. The concave cutter is especially useful when you want to prune a branch close to the trunk and don’t want scar tissue to form on the place of the cut. Of course there are no guarantees, but using the concave cutter will leave a clean cut that can heal easily, leaving little to no scar.
When not to use it?
Do not use the concave cutter if you are looking to create scar tissue on branches or the trunk of your bonsai tree. Also, don’t attack the smaller twigs and branches with this tool. You are more likely to hurt the tree or yourself than when you use a smaller branch cutter or scissors.
For a comprehensive overview of all bonsai tools and their application, check out the Daily Bonsai Tools Wiki page.