The pen cap mystery

[Bottom Line]

Does anybody know how a pen manufacturer gets the cap band on a cap? This has always been a total mystery to me. I've tried to remove a few - never successfully. Brute force just doesn't work. I know the answer must be simple.

 

Ray

[antoniosz]

I am not 100% but one possibility is the swaging process that can be done either like this:

 

http://www.torrington-machinery.com/images/pic_rotary_swaging1.gifhttp://www.torrington-machinery.com/images/pic_rotary_swaging2.gif

 

or like this:

 

http://www.torrington-machinery.com/images/pic_stationary.gif

 

Pictures "stolen" from http://www.torrington-machinery.com/process/swaging.html

[Bottom Line]

Is this a machine that puts even pressure on all the way around while it pushes the ring onto the cap? That is what I'm getting from the picture.

 

My problem is how do you get a ring to pass over a part of the cap that is larger than the ring without fracturing the cap? I'm not sure how this machine can overcome the stresses to the plastic without distorting the plastic.

 

I always thought that you might heat the metal ring so it expands and then drop it over the cap and then cool the ring? But, what if the ring is too hot? Won't it melt the cap?

 

I figured it must be something that is pretty simple because everybody uses cap rings. There can't be a super mystery because all the manufacturers could do it. It wouldn't exactly be a trade secret.

 

Ray

[Dillo]

Hi,

 

It is done be stretching the band, then shrinking it with rollers. Pelikan bands are different, they are placed by an injection moulding process.

 

Dillon

[Richard]

Several modern manufacturers make the cap in two parts. On a Parker Duofold, the lip piece screws up inside the body of the cap after the assembler slips the band onto the lip piece. On a Filcao Columbia or Atlantica, the lip end of the cap body is smaller than the outside diameter. The assembler slips the band onto the cap body and then glues another band, of body material, in place to hold it.

[Vintagepens]

As far as I know, most older cap rings were crimped in place ("segmented swaging", in the parlance of the site referenced above).

 

The notion of expanding and shrinking by heating and cooling is mistaken.

The coefficients of expansion for both the plastics and metals used are far, far too small.

[Greg]

...and also if you place hot metal on plastic it will melt it!

 

Thanks to all for the comments on this little conundrum.

 

I have just received a little Croxley from the dreaded *b*y, which is very nice, for £3, but has a loose cap band. Not having a swageing roller milling machine I shall be applying a little super-glue.

 

 

Greg

[twdpens]

I wouldn't recommend generic super-glue as it can leave a nasty "bloom" trace. There are some grades of cyanoacylate that are low-bloom but these are probably not available in normal hardware shops.

 

Martin

[tryphon]

...and also if you place hot metal on plastic it will melt it!

 

Thanks to all for the comments on this little conundrum.

 

I have just received a little Croxley from the dreaded *b*y, which is very nice, for £3, but has a loose cap band. Not having a swageing roller milling machine I shall be applying a little super-glue.

 

 

Greg

The best adhesive for loose cap bands is shellac.

Apply with a toothpick, let dry and remove any excess with ethyl alcohol.