Fixing Loose Threaded Caps

[Russ]

Numerous pens have earned a NOGO designation inasmuch as they uncapped in my pocket at work, leaving a stain to occupy my off-duty hours: Waterman Commando, Conklin Endura, Pelikan 140, Pelikan 400 (new style), Stipula Ventidue, and others.

 

I don't like the idea of putting adhesive tape on the section or threads. The adhesive becomes icky in hot weather. Tape will peel loose and need to be replaced. Teflon tape will look cheap and fall off. I am thinking of placing a small dot of clear silicone RTV sealant where the cap lip arrives at the end of its arrival upon the barrel in order to snug it up. I remember using this when sealing aquariums. Question: Will this silicone damage the barrel? Its strong vinegar smell leads me to respect its qualities ... maybe too strong for pen use.

 

Ideas?

[BamaPen]

I don't have an answer to your silicone question, but I have had some success with a loose cap using tape. I put the tape INSIDE the cap on the threads there and it has worked just fine. It does not show and so far has not gotten sticky. I used a type of tape that is used in mounting pictures for framing. It is not extremely sticky, white in color, Ph neutral, and fairly thin. Seems like an ideal, totally reversible solution to me. In the case of my cap, the threads had worn, or plastic has shrunk, so that there was no engagement at all. But, if yours is just loose, you may find that less than a full turn of tape would be sufficient - just a small patch, for example.

[fountainbel]

In my opinion the only proper way to restore a loose thread fit is heat expanding the section and/ or heat shrinking the cap .

At least if the thread profiles are still deep enough and in relatively good shape.

I've done this on several pens with excellent results.

When there is still some threadfit , and the threads just disengages when the section front hits in inner cap collar, one could shorten the inner cap for 1- to 1.5mm so fresh cap threads will engage.

However first check if the nib point would not hit before doing this !

Shortening the section collar at the threadside is an " in last instance" possibility, personally I'm not however not in favour doing so.

Francis

[Russ]

I don't have an answer to your silicone question, but I have had some success with a loose cap using tape. I put the tape INSIDE the cap on the threads there and it has worked just fine. It does not show and so far has not gotten sticky. I used a type of tape that is used in mounting pictures for framing. It is not extremely sticky, white in color, Ph neutral, and fairly thin. Seems like an ideal, totally reversible solution to me. In the case of my cap, the threads had worn, or plastic has shrunk, so that there was no engagement at all. But, if yours is just loose, you may find that less than a full turn of tape would be sufficient - just a small patch, for example.

 

I like this suggestion. It is invisible from without, inexpensive, and effective. At least until new tape is needed (!).

[Russ]

In my opinion the only proper way to restore a loose thread fit is heat expanding the section and/ or heat shrinking the cap .

At least if the thread profiles are still deep enough and in relatively good shape.

I've done this on several pens with excellent results.

When there is still some threadfit , and the threads just disengages when the section front hits in inner cap collar, one could shorten the inner cap for 1- to 1.5mm so fresh cap threads will engage.

However first check if the nib point would not hit before doing this !

Shortening the section collar at the threadside is an " in last instance" possibility, personally I'm not however not in favour doing so.

Francis

 

A pertinent question is whether heating a given section will expand it or cause it to contract still further upon cooling. I wouldn't want to make a modesst problem worse. I think experimenting with the cap would be the best approach at first; it likely won't expand and stay expanded upon cooling. Is this correct reasoning?

 

Thanks for this and the other two suggestions. I'll have to think carefully!

[fountainbel]

In my opinion the only proper way to restore a loose thread fit is heat expanding the section and/ or heat shrinking the cap .

At least if the thread profiles are still deep enough and in relatively good shape.

I've done this on several pens with excellent results.

When there is still some threadfit , and the threads just disengages when the section front hits in inner cap collar, one could shorten the inner cap for 1- to 1.5mm so fresh cap threads will engage.

However first check if the nib point would not hit before doing this !

Shortening the section collar at the threadside is an " in last instance" possibility, personally I'm not however not in favour doing so.

Francis

 

A pertinent question is whether heating a given section will expand it or cause it to contract still further upon cooling. I wouldn't want to make a modesst problem worse. I think experimenting with the cap would be the best approach at first; it likely won't expand and stay expanded upon cooling. Is this correct reasoning?

 

Thanks for this and the other two suggestions. I'll have to think carefully!

 

Logically you have to expand the barrel gradually during the heat-up process in a mechanical manner.

I use the inner cap puller sold by Woodbin for doing so.

Given the inner barrel threads, I make/use a small nylon bushing which just fits in the barrel threads, with a bore fitting over one of the smaller collets.

The nylon bushing features a length wise slit, so it expands easily.

I first measure actual diameter of the threaded barrel end so I know were I started before expansion.

After installing the bushing and the collet in the bore, I heat-up the threaded circumferene of the barrel and gradually expand the barrel end screwing the inner cap puller thighter.

Measure regularly how expansion evolves

An expansion of 0.2 mm is mostly enough , otherwise one risks the inner section thread becomes to sloppy.

Let cool down before loosing the innner cap puller tension, so the material is set.

When the cap /barrel threads are still to sloppy, you have to shrink the cap threads also

I use a miller tool holder with exchangeable collets to do so, the same tool I use for swaging loose cap rings.

I posted before on my swaging method, just search under "swaging" on this board.( see link below)

Also in this case I make/use a slit bushing having a length slightly longer as the length of the inner cap threads.

Simular procedure : heat- up, install cap/bushing in the tool collet and gradually thigten the collet by screwing the tool nut on.

Francis

 

My "swaging"link

https://www.fountainpennetwork.com/forum/index.php?/topic/68596-shearing-my-method-for-capring-swaging/page__pid__949558#entry949558

 

Edited for completion and adding "swaging" link

Edited March 25, 2011 by fountainbel

[framebaer]

It should be noted here that different plastics expand, compress to different degrees.

 

Vintage celluloid works best (imho) more modern acrylics much less so and Hard Rubber works but can be tricky.

[fountainbel]

It should be noted here that different plastics expand, compress to different degrees.

 

Vintage celluloid works best (imho) more modern acrylics much less so and Hard Rubber works but can be tricky.

 

Thanks framebear !

I completely agree, celluloid is the easiest, HR is more risky for cracking, never done it on modern acrylic's.

Important is to expand slowly and gradually with intermediate heat-up.

Francis

[Russ]

Okay. Now I can see it in my mind.

 

Fountainbel, you give great advice.

 

A few months ago I sold my '48 John Deere two-cylinder, and have been trying to downsize my garage. We moved to a new home, and went from a three-bay garage to a much smaller setting. If I begin buying tools again . . . I'm going to feel motivated to go in the direction of pen repair for good. Maybe I should. I'm a perfectionist who likes to create order out of chaos.

 

I guess I'll begin by reading the penmaking forum and learn more.

[viclip]

FYI as a general observation, instead of using regular silicone sealer & being concerned with the vinegary output, use Silicone II instead which doesn't emit acetic acid as it sets (aka vinegar).

 

Table vinegar won't hurt plastic pens however I'm unsure as to the concentration of the acetic acid contained in regular silicone sealers. Back in my motorhead days we avoided using regular silicone sealer anywhere there could be moisture since the acidic content could form a corrosive solution that would devour metal.

 

These are just a few observations about using the acidic vs. non-acidic versions of silicone sealer/caulk...I recommend following the advice of Fountainbel et al. as to proper repair methods for pen thread issues.