Reaming Out An Inner Cap?

[takkun]

Hi all,

 

A while back I was having an issue with my pen leaking all over the cap. After much frustration, numerous disassemblies and cleanings, and changing inks, I figured out that my nib was contacting the inside of the sprung inner cap. (It's a MB 121, for the record)

I've since removed the offending piece, and no more leaks. But perhaps a more dire issue has come up: The cap isn't totally snug, and now the section is free to rub against the inside should there be any pressure on the cap.

 

Any ideas how I should go about fixing this? These particular Mont Blanc parts are hard to come by.

[kirchh]

Hi all,

 

A while back I was having an issue with my pen leaking all over the cap. After much frustration, numerous disassemblies and cleanings, and changing inks, I figured out that my nib was contacting the inside of the sprung inner cap. (It's a MB 121, for the record)

I've since removed the offending piece, and no more leaks. But perhaps a more dire issue has come up: The cap isn't totally snug, and now the section is free to rub against the inside should there be any pressure on the cap.

 

Any ideas how I should go about fixing this? These particular Mont Blanc parts are hard to come by.

 

If there was a problem with the fit of the inner cap -- an essential component of the pen, presumably included for good reason by the designers -- it would not seem sensible to simply remove it and expect that there would be no consequences from the omission of such a part.

 

Was something actually wrong with the inner cap (or with another part of the pen) that was causing an improper fit (if it was actually improper)?

 

--Daniel

[Ron Z]

You do find that the ID of the inner cap is a bit small on occasion, and the shoulders of the nib hit the inner wall. Not all that common, but it happens. I bore out the inner cap on the lathe to increase the ID just a tad so that the nib clears the inside walls of the inner cap. Drilling can be done, but it's risky because there are only two cutting points, and they can grab and crack the inner cap. Especially a possibility with a hard rubber inner cap. A reamer would be safer if you can find one of the right size. Even boring it out with a drill or a reamer is better done on the lathe. High speed, very light cuts are best.

[kirchh]

You do find that the ID of the inner cap is a bit small on occasion, and the shoulders of the nib hit the inner wall. Not all that common, but it happens. I bore out the inner cap on the lathe to increase the ID just a tad so that the nib clears the inside walls of the inner cap. Drilling can be done, but it's risky because there are only two cutting points, and they can grab and crack the inner cap. Especially a possibility with a hard rubber inner cap. A reamer would be safer if you can find one of the right size. Even boring it out with a drill or a reamer is better done on the lathe. High speed, very light cuts are best.

 

I'm not sure that applies here; I think the inner cap is plastic, and the nib on a MB 121 is streamlined and really has no shoulders, being narrower than the forepart of the section from which it emerges. The OP didn't specify what part of the nib was contacting the sprung inner cap -- side or tip. Perhaps he will add some details.

 

--Daniel

[takkun]

Thanks for the responses. I did know it was an essential part, and didn't mean for it to be a permanent fix--just trying to isolate the cause (other guesses: a cracked reservoir, weak piston seal, improper piston alignment).

 

It is a narrow semi-hooded nib (the earlier one, seated inside the section and not push-fit from the front), and as such, doesn't have any protrusions to rub against the side the way an open nib might, but when its seated, it does contact the sides of the nib, where the nib and feed meet the hood. Hence the thought to perhaps ream it out. We're talking a good half-capful leaking out, and not a drop without the inner cap.

 

My guess is it's some sort of vinyl, perhaps PVC, and definitely not hard rubber. I have access to a lathe, so perhaps I'll attempt making a new piece when I get some spare time.

[kirchh]

It is a narrow semi-hooded nib (the earlier one, seated inside the section and not push-fit from the front), and as such, doesn't have any protrusions to rub against the side the way an open nib might, but when its seated, it does contact the sides of the nib, where the nib and feed meet the hood.

 

Are you sure the nib was contacting the inner cap? The nib is slightly narrower than the section shell, so I would think the shell would contact the inner cap before the nib would.

 

--Daniel

[takkun]

Best I can tell, something's contacting something.

I popped the inner cap on the inked pen and left it for a few minutes. Came back to this.

Any thoughts?

http://i.imgur.com/N1O96pC.jpg

Apologies for the less-than-stellar iPhone photo; I no longer have a DSLR. It's hard to tell, but there's an even ring of ink reaching about halfway from the nib to my finger and around the edges of the nib.

Edited February 3, 2015 by takkun

[kirchh]

Best I can tell, something's contacting something.

 

Well, the inner cap is supposed to contact the section, and I believe it's spring-loaded to maintain a seal when the pen is capped, as the cap is secured with a positive stop; a fixed inner cap might not be perfectly positioned, so the floating arrangement makes sense.

 

I wonder if there is excess ink in the feed (perhaps due to a slight breach in a seal at the rear), and when the pen is uncapped, the momentary suction draws a drop or two of ink out of the feed. Most pens are designed with some sort of vacuum breaker (vent hole/slot/groove) so this phenomenon is minimized (and pens should really be uncapped when held point-up), so I'm not sure why it would be happening here.

 

--Daniel