Come back to a cut you made a season or two ago and sometimes you'll find the wound healed into a raised knob rather than lying flush — even when you used a concave cutter the first time around. It happens on thicker branch unions and old jin sites more often than growers expect, and there's a specific tool built to correct it.
A second pass, not a first cut
A knob cutter's rounded jaw is shaped to cleanly scoop out a raised or healed-over knuckle of wood, taking the wound back down to flush without gouging into healthy surrounding bark. It's not the tool you reach for on a fresh cut — that's a concave cutter's job — it's the tool for correcting a union that healed proud, or for finishing an old jin scar that never quite closed level. Growers working with mature material, collected yamadori, or trees they've owned for many seasons, tend to reach for this one more than beginners do, simply because more of their trees have old wounds worth revisiting.
Built to take the load
Removing a healed knuckle means cutting through denser, often partially calloused wood — tougher material than a routine branch removal. A stainless steel jaw alloyed with manganese is what lets a knob cutter's rounded edge hold up to that repeatedly without rolling or losing its scoop shape, and the stainless base keeps it corrosion-free between the occasional sessions it actually gets used for, since this isn't a tool most growers reach for every week.
Who actually needs one
If your collection is young or you're working mostly from nursery stock, you may go a long time before a knob cutter earns its keep. If you're working mature or collected material with a history of old cuts, it closes a gap that a concave cutter and a pair of scissors genuinely can't cover on their own.
Knob Cutter at Bonsai Den
We're adding the Core Series Knob Cutter to the shop shortly — check back here for the direct link once it's live. In the meantime, our Core Series Concave Cutter, 180mm handles the first cut cleanly, so fewer of your wounds need a knob cutter's correction down the line.