Loose cap is a pretty common issue on Montblanc Noblesse, as for many other pens with a plastic snap inner cap.
Plastic inner caps usually have a shorter life than the ones with metal mechanism, as they become loose over years of use by the friction of capping and uncapping.
Fixing this issue can be not so easy.
A fast search in the web gave back a range of proposed solutions:
- a single layer of electrical tape around the bottom of the inner cap, as it could pull back the inner cap in shape;
- a layer of Teflon tape on the clutch ring on the section (with an high risk of inner cap cracking);
- a little piece of cellophane tape inside the cap (with or without silicon grease to increase the adhesion);
- a thin layer of superglue or epoxy inside the bottom of the inner cap (a dangerous no-return method, in my opinion) in order to increase the grip coupling;
- a drop of boiling water into the cap, in order to soften and re-shaping the inner cap.
Discarding the #4 because irreversible, and the #5 because too uncertain, I applied all the first three methods, but without success.
So I planned to experiment a personal appoach, which brings together some of the theoretical assumptions of the methods #1 to #3.
After unscrewing the topper with the MB star, I released the inner cap and clip (figure #1).
Then I put a ring of a thermo-shrinkable tube (5 mm in height, 9.7 mm in diameter) around the bottom of the inner cap (figure #2).
Using a lighter, I quickly heated the inner cap together with the thermo-shrinkable ring. The heat softened the inner cap plastic and at the same time shrank the ring (figure #3), reshaping the inner cap.
Then I gently removed the shrunk ring (figure #4) and finally put the reshaped inner cap into the cap, screwing on the MB star cap top.
The cap clicks nicely and firmly, now.
Sincerely, I cannot predict how long the reshaping will last, but surely I will report the long term outcome of this matter.