First, you need to identify where the scratch is coming from, whether it is the outer visible tipping or the inner tines. Normally the outer parts are quite well smoothened by manufacturers, except some Japanese brands where, i cannot confirm if it is intentional or otherwise, they leave some angled cuts. I have seen this with Pilot Custom, Sailor gold nibs.
Normally the scratch, for me, comes from the inner tines. At writing angle, 2 tines do not always meet the paper completely, especially at loops or in bigger and faster writing. The pressure at the 2 tines will almost always be different. This exposes the inner tines to the paper.
Some manufacturers round the inner tines pretty well, e.g. my Pelikan m800. Whereas some manufacturers leave the inner tines rather unfinished, e.g. my Sailor gold nibs. No problem with the Sailors as long as the tines do not have too big a gap.
Jinhao nibs are actually quite smooth. If you get them to practise smoothing, you will be unsmoothing them, possibly creating sharper inner tines as a result. (A new problem created) Then trying to smooth them again.
It depends also on how big a gap you want the tines to separate at the tip. A big gap demands real smooth and rounded inner tines. A small gap is usually more forgiving of the inner tines because the 2 tines work as one, not as 2 or 3 or 4.
Therefore, closing the gap between tines can sometimes make a pen write smoother. (But this does not solve the actual problem because if you write with slightly more pressure, the inner tines are exposed to paper again)
These are points I did not see on the attached notes by both Binder and Ludwig Tan. But Binder addresses the issue of inner tines.
Practice is a good thing only when it is done in the correct direction. The essence is to identify the problem, not trying things out and 'practising' haphazardly.
It certainly helps to have high powered magnification with ample lighting so that you can observe and take notes of what you have done to the nib(s).
And sometimes, fingernails are your best friend, not always abrasive films.
No mountain is too micro because it will be felt, especially when you want glass smooth writing.
Edited by minddance, 18 January 2019 - 01:37.