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Concave cutter vs knob cutter

Updated: 22 October 2026

Two short, heavy cutters sit side by side in a set photo on amazon.co.uk. One is a concave cutter, also called a branch cutter. The other is a knob cutter, sometimes sold as a spherical cutter. They look close enough that the knob cutter comes out first. This concave cutter vs knob cutter page keeps the jobs apart: the branch cutter takes the branch off, and the knob cutter only reshapes what is still proud of the wound. The listings are in the [bonsai tools comparison](/hub/garden-tree-and-hedge-shears/bonsai-tools). Peter F. checked the contents lines. A qualifying purchase can earn a commission at no extra cost to you.

Two short, heavy cutters sit side by side in a set photo on amazon.co.uk. One is a concave cutter, also called a branch cutter. The other is a knob cutter, sometimes sold as a spherical cutter.

Our top picks

Penitue Penitue 3-piece stainless cutter set

Best overall

Penitue Penitue 3-piece stainless cutter set
6.4/10about £28.99
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VOUIU VOUIU 6-piece set with trunk splitter

Rank 2

VOUIU VOUIU 6-piece set with trunk splitter
9.2/10about £69.97
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VOUIU VOUIU 5-piece bonsai cutter set

Alternative

VOUIU VOUIU 5-piece bonsai cutter set
8.4/10about £60
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On this page
  1. 1.They are not two names for one tool
  2. 2.Remove the branch, then look, then refine
  3. 3.If you buy only one of this pair
  4. 4.What a millimetre figure on the title measures

They are not two names for one tool

A concave cutter is the branch cutter in Suwada's split. The jaw is curved, it takes the branch off, and the bite leaves a shallow hollow where the branch met the trunk or a larger limb. A knob cutter has the rounder jaw. You use it afterwards, when a stub or a lump still stands proud of that wound. Some shop pages treat the two names as one tool. Bonsai Club Tokyo's guide keeps the jobs separate, and these amazon.co.uk listings name two tools when both are in the box. Penitue's page uses ball-joint pliers and diagonal pliers as well as knob cutter and concave cutter. Match the jaw in the photo to the job. The jaw that severs the branch is the concave cutter.

Remove the branch, then look, then refine

Suwada's sequence is remove, inspect, and refine only if something still needs it. On an established branch you start with the concave cutter. Set the curved jaw so the cut sits close to the trunk or to the parent limb, and take the branch off in that bite. If a stub, a ridge, or a lump still stands above the surrounding bark, the knob cutter is the tool for that remainder. Bonsai Club Tokyo's guide is particular about that second bite. Shorten a long stub first, take small bites, and keep the jaw from twisting in the wood. When the concave cut is already a clean hollow, the knob cutter stays in the pouch. A swelling that is the tree sealing the wound is healing wood, and that guide warns against cutting every raised callus as if it were a knob.
Penitue Penitue 3-piece stainless cutter set

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Penitue Penitue 3-piece stainless cutter set
6.4/10about £28.99
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If you buy only one of this pair

Suwada's beginner order is scissors, then a branch cutter, then a knob cutter. When the budget covers one of this pair, buy the concave cutter, because it is the tool that removes the branch. A knob cutter on its own leaves the branch on the tree. If you already own a branch cutter and the cuts keep leaving lumps, the missing tool is the knob cutter. Four listings here name both cutters: the VOUIU five-piece, B088DV5244, the VOUIU six-piece with a trunk splitter, B07YCMTWRV, the VOUIU six-piece with a root hook, B0C697LXSK, and the Penitue three-piece, B0GVH1CDQ3. Wazakura, YZNlife, Wobodan, Omticova, and both HJHJLA listings do not, so a large piece count still leaves this pair unsolved. What else sits in the pouch is the bonsai tools buying guide.

What a millimetre figure on the title measures

A 210 mm line on a VOUIU listing is the length of the tool. Miyagi Bonsai's beginner guide treats 180 mm as their beginner size. Their guides also carry a 15 mm figure for their own cutters, and the same pages disagree on a 200 mm cutter's branch limit: one line says about 12 mm, and another says about 20 mm. Neither line is a test of the VOUIU or Penitue ASINs above. When a listing here prints a length and stays silent on branch thickness, the thickness stays unstated. These cutters were not laboratory-tested.

Common questions

Can a knob cutter remove a whole branch?
The knob cutter reshapes a stub or a lump after the branch has gone. On wood that is still attached, use the concave cutter. That swap is the usual mistake when the two jaws look alike in a set photo. Take the small bites Bonsai Club Tokyo describes, without twisting the jaw.
If the hollow is already clean, do I still use the knob cutter?
Leave the knob cutter in the pouch when the concave cut is already a clean hollow and nothing stands above the bark around it. A second bite on a flush wound makes a deeper scar for the callus to cover. Save the rounder jaw for a remaining bump. A raised healing callus is the tree closing the cut, and Bonsai Club Tokyo warns against treating every swelling as a knob.
Do I need both a concave cutter and a knob cutter?
You need the concave cutter once you remove woody branches. You need the knob cutter when those cuts keep leaving stubs or lumps that still stand proud. If the budget is one tool, follow Suwada's beginner order and buy the branch cutter first, then add the knob cutter when you are refining wounds.
Which of these sets include both cutters?
The VOUIU five-piece (B088DV5244), the VOUIU six-piece with a trunk splitter (B07YCMTWRV), the VOUIU six-piece with a root hook (B0C697LXSK), and Penitue (B0GVH1CDQ3) name both. Wazakura, YZNlife, Wobodan, Omticova, and both HJHJLA listings do not. On Penitue, match the jaw in the photo, because ball-joint pliers and diagonal pliers appear beside the cutter names.
Is 210 mm the thickness of branch the cutter can take?
On the VOUIU listings here, 210 mm is the length of the tool. Miyagi's 180 mm beginner size, the 15 mm figure, and the split of about 12 mm and about 20 mm on a 200 mm cutter are that seller's own guides. They were never a test of these ASINs. When the listing gives a tool length and no branch limit, the branch limit stays unstated.
What happens if every wound is cut deeper?
Each extra bite takes wood the callus then has to grow across. Bonsai Club Tokyo's guide asks you to shorten a long stub first, to take small bites, and to leave a raised healing callus alone. A routine second hollow on a flush cut is the risk you can skip.

Related pages

How to use bonsai tools

Best bonsai tools

Bonsai tools

Bonsai tool set for beginners: what the bag must cut

Bonsai tools buying guide before you open the pouch

Sources

Public UK sources used for this comparison. Listing prices, stars, and review counts are from amazon.co.uk on 21 October 2026.

  1. Miyagi Bonsai — beginners' guide to branch cutters (retrieved 21.10.2026)
  2. Suwada — essential bonsai tools (retrieved 21.10.2026)
  3. Suwada — branch cutter vs knob cutter (retrieved 21.10.2026)
  4. RHS — bonsai (retrieved 21.10.2026)
  5. RHS — sharpening tools (retrieved 21.10.2026)
  6. General Product Safety Regulations 2005 (retrieved 21.10.2026)
  7. Consumer Rights Act 2015, section 9 (retrieved 21.10.2026)
  8. Bonsai Direct — how long to leave bonsai wire on (retrieved 21.10.2026)