Concave Cutter vs. Knob Cutter: Which Bonsai Tool Does What?

Concave cutters and knob cutters often sit next to each other in bonsai catalogs. Both remove wood, and both can leave a hollowed area. The distinction is mainly about the shape of the cut and the kind of material being removed.

Concave branch cutters: removing a branch near the trunk

A concave branch cutter is designed to remove a branch close to the trunk while leaving a shallow recessed wound. The cutting profile helps avoid a raised stub that would remain visible as the tree develops. It is intended for structural pruning, not routine trimming of shoots and leaves.

Niwaki’s US-facing listing for the Kaneshin No.3 branch cutter describes a carbon-steel, Japanese-made tool with one-inch blades. The retailer gives a recommended capacity of up to 12 mm for concave cuts. That figure belongs to this specific listing; it should not be treated as a general capacity for all branch cutters. The earlier research snapshot showed $110, but current price and stock should be checked directly.

Knob cutters: working back raised wood

A knob cutter has rounded, bulb-like jaws. It is commonly used to remove protruding stubs, old knobs and raised areas, or to take wood back further when refining an existing cut. Its rounded head can make a deeper, more rounded hollow than a conventional branch cutter.

The jobs are not completely separate. A practitioner may use a knob cutter for some branch-removal work, and manufacturers do not always use the same English name for similar-looking tools. That is why the jaw profile and the maker’s description matter more than a translated catalog label.

Which one belongs on your bench?

If you are removing a branch close to the trunk as part of structural development, a concave branch cutter is the more direct tool to consider. If you are dealing with raised stubs or shaping a protruding area, a knob cutter may be more useful. A beginner maintaining young trees may not need either one yet.

Before ordering, compare the head shape in clear product photographs, confirm the model number, and read the manufacturer’s intended use. Terms such as “knob”, “knuckle”, “spherical” and “concave” are sometimes translated inconsistently. Two tools with similar names may not have the same jaw geometry.