How to Remove Nub Marks
The difference between a kit that looks assembled and a kit that looks built is about thirty seconds per part.
The short answer
Cut twice: leave the nub 1-2 mm proud when you free the part, then trim it flush once nothing is under tension. Shave the remainder flat with a fresh knife blade using light passes, then sand with 400 and 800 grit. White stress marks need sanding out or covering with paint — nothing else hides them.
The quick version
| # | Product | Best for | Score | Price |
|---|---|---|---|---|
| 1 |  Olfa Art Knife (AK-4)A slim aluminum handle with a genuinely sharp, cheap, replaceable blade. The blade supply is the real argument — a dull knife is what tears plastic. | Shaving the nub flat | 9.2 | Check price on Amazon |
| 2 |  Hobby sanding sticks (assorted grits)Foam-backed abrasive on a stick, in a grit range from coarse to polishing. The thing that turns a visible nub into no nub at all. | Taking out the knife marks | 8.7 | Check price on Amazon |
| 3 |  Tamiya Sharp Pointed Side CutterSlim, pointed jaws that get into a crowded runner, in a tool sturdy enough to survive years of ordinary use. The sensible first buy. | A cut that needs less cleanup | 9.0 | Check price on Amazon |
Scores are our own editorial read against the criteria stated below — not a lab measurement and not a user rating. Tap a row for the full write-up.
Why cutting twice is the whole technique
When a part is still attached, the gate is under tension. Cut it flush in one pass and the blade drags the plastic as it severs, which tears a small crater out of the part surface or compresses the plastic until it turns white.
Cut 1–2 mm away first and the part falls free with no stress. The leftover nub is now a free-standing stub you can trim at your leisure with nothing pulling on it. This single habit removes most nub damage, regardless of which nipper you own.
Knife technique
The knife does the precision work, and three details decide whether it helps or hurts.
The blade must be fresh. A sharp blade slices plastic; a blunt one pushes it and leaves a white dragged scar. Blades are cheap and this is the most common cause of a bad result.
Almost flat to the surface. Lay the blade nearly parallel to the part and shave, taking the nub down in several light passes. Holding the knife at an angle digs in and takes part surface with the nub.
Shave across, not into. Move the blade sideways across the nub. Pushing toward the part is how you gouge it.
On curved surfaces, follow the curve with short passes rather than trying to take the nub in one sweep, and expect to finish with sanding rather than the knife.
Sanding, and the mistake everyone makes
A shaved nub is flat but shiny in a different way to the molded surface around it, which is why it is still visible. Sanding equalizes the texture.
Use 400 grit to flatten, then 800 to remove the 400’s scratches. On a part you intend to leave unpainted, go further — 1000 then 1500 — and the area becomes genuinely invisible.
The mistake: rocking the sanding stick, which rounds off the crisp panel edge next to the nub. A rounded edge is more noticeable than the nub was. Keep the stick flat and work only the nub area.
Fixing white stress marks
Stress whitening is not surface dirt. The plastic itself has been deformed at a structural level, which scatters light. Nothing cleans it off.
Three real options:
- Sand it away, if the whitening is shallow. Often it is only in the top fraction of a millimeter.
- Cover it. Paint or a matching marker over the area is the usual fix on a visible panel.
- Prevent it next time. Cut twice, sharp blade, no twisting. That is the whole prevention list.
Clear and white parts show whitening worst and are the least forgiving. Cut those with extra margin.
Checking your work properly
A nub mark you cannot see looking straight down will often be obvious once the model is assembled and light rakes across the surface. Check each part at a shallow angle under a lamp — this is also where a magnifier earns its keep.
One shortcut worth knowing: if you are going to prime and paint the kit, prime early and inspect. A thin coat of primer makes every remaining nub, seam and scratch visible in a way bare plastic does not.
The picks in full
Olfa Art Knife (AK-4)
A slim aluminum handle with a genuinely sharp, cheap, replaceable blade. The blade supply is the real argument — a dull knife is what tears plastic.
What it gets right
- Blades are cheap enough that you will actually change them, which is the whole game
- The 30-degree point gets under a nub without gouging the part
- Slim handle is comfortable for the long, careful passes nub removal needs
Who it is wrong for
- The slim barrel rolls off a desk, and a rolling scalpel is a genuine hazard
- Blades are brittle at that angle; levering with one snaps the tip
- No cap on some versions, so budget for a safety cap or a blade block
Scored against this page’s criteria
We do not publish prices. Amazon shows the current one, which is the only one that is ever right. #ad · how this is funded
Hobby sanding sticks (assorted grits)
Foam-backed abrasive on a stick, in a grit range from coarse to polishing. The thing that turns a visible nub into no nub at all.
What it gets right
- Foam backing follows a curved surface instead of flattening it
- A progression of grits removes the nub AND the sanding marks it leaves
- Usable wet, which stops the clogging and the plastic dust
Who it is wrong for
- Coarse grits leave scratches that will show through paint unless you work up through the finer ones
- Sticks wear out and clog; they are consumables
- Sanding a painted or pre-colored part means repainting it, which beginners discover the hard way
Scored against this page’s criteria
We do not publish prices. Amazon shows the current one, which is the only one that is ever right. #ad · how this is funded
Tamiya Sharp Pointed Side Cutter
Slim, pointed jaws that get into a crowded runner, in a tool sturdy enough to survive years of ordinary use. The sensible first buy.
What it gets right
- The pointed jaw reaches gates that a fat double-blade cannot get near
- Tough enough to cut thicker sprue without worrying about the blade
- Roughly a third of a God Hand, and it will not be the thing limiting your build quality
Who it is wrong for
- A double blade pinches, so it leaves more of a stress mark than a single blade
- You will still want a knife or a sanding stick to finish the nub
- Not as satisfying to use, which matters more than it should
Scored against this page’s criteria
Specs from the manufacturer: Tamiya product page
We do not publish prices. Amazon shows the current one, which is the only one that is ever right. #ad · how this is funded
FAQ
Questions people actually ask
How do I remove nub marks without white marks?
Can you fix white stress marks on plastic?
What grit sandpaper for Gunpla nubs?
Should I use a file or a knife on nubs?
Why can I still see the nub after sanding?
More in Model Kit Tools for Gunpla and Scale Models, or start from the beginning with what to buy first.
Sources
- Tamiya — tools, cement and panel line accent colorchecked October 2026
- Bandai Spirits / Gundam official kit and grade informationchecked October 2026
- God Hand — Ultimate Nipper specificationschecked October 2026