Gunpla Basic: Nub Marks Removal

Credit to Landel ::::: 

"""Hi guys, here is my tutorial for removing nub marks for unpainted builds. I don't believe many people actually do unpainted builds but for those beginners that actually don't have airbrush or who want to use minimal spray cans (only topcoat needed) but still want to achieve a nice looking kit, then I hope you will find this tutorial useful. This is just my own method of removing the nub marks but feel free to experiment and come up with your own.

Because the build is unpainted and all you do after assembling is spray topcoat, the quality of the nub marks becomes more obvious if the plastic turns white due to "yielding". The idea is not to have any white marks on the plastic, which will make your kit look ugly.

The whitening of the plastic happens when the plastic is bent beyond its yield point. Normally this happens during the cutting of the sprue. Hence, this tutorial will show how to cut the plastic part out from the sprue without leaving white marks.

On white colour plastic, even if the plastic yields, since it's already white, the white marks aren't really obvious and you won't have to spend so much time trimming the plastic"""" - Landel 

The part in question we want to remove is circled in red.

The other parts of the plastic sprue tree are also indicated.
We want to cut the gate as far away from the plastic part as possible. That way, when the plastic yields, it will yield away from the precious component. If the gate is too small, just cut away the whole runner.

Cut away from the part!

Notice how after the part is cut, the cut area turns white?

This is because the nippers start to squeeze and bend the part before the part is actually cut.

After cutting the other two gates, you can see how white the gate becomes.

Next, use a pair of very very sharp (new) flush cutters, and start slicing away the offending nub mark starting as near to the top as possible. It's very important to use super sharp cutters, and to make your slices as thin as you possibly can. That way, instead of squeezing and bending the plastic, you slice the plastic instead. You need to make many cuts before you reach the base. 

Note: On RG kits, they have a self-aligning gate which guides the nipper flush onto the base of the component. Do not use the self-aligning guide!

After removing the very first layer. Notice how the bottom is still white? That's because part of it turned white in the very first step when removing the part from the gate. Continue to make thin slices with your nippers.

After making many slices. We have reached as far down to the plastic as possible with nippers. The nippers are unable to remove anymore plastic. Notice it's not white anymore.

For the next step, we use a super sharp modelling knife with brand new blades. I only use Olfa AK-3 with a brand new blade. Slowly rest the knife flat on the edge of the workpiece, then slice thinly across the remaining nub mark. Once again, don't get greedy here and slice as thinly as possible.

Slice thinly!

After first layer is sliced.

After slicing until the plastic is almost flush. Notice how thin the shavings are?

Next, we sand down the surface. I personally use 800 grit sandpaper for this.

After 800 grit sandpaper, the surface of the plastic looks cloudy and different colour from the rest.

In order to remove the cloudy, scratched and matte surface, I use a 3 step fingernail buffer (or nail polisher) to shine it back to its original gloss.

After first step of buffing.

After second step of buffing. It's almost back to its original shine but some fine scratches remain.

After final step of buffing. The nub mark has disappeared and it's ready for assembling (and topcoat if desired)!