How Do Pen Inserts Stay In Place?

[mingus]

Hi

 

I am designing a pen and was wondering if anyone has insight into how the cap liner/insert stays in place. Is it friction? Or is there an adhesive applied?

Also, if anyone knows where you can buy plastic cap liners/inserts, that would be great!

 

Thanks!

[Ron Z]

It depends on the pen and the manufacturer. In many cases, the inner cap is simply a friction fit, especially on vintage pens. Adhesive is rarely if ever used since it would make it difficult to get the inner cap out when needed. Some pens however have the inner cap that is held in by a screw. Many Italian pens like my Aurea and the Omas Tokyo use a pin on the top of the inner cap to hold the clip in place, with threads on the outside of the inner cap so it screws into the cap. Pelikans have the ring above the clip that holds it in, Parker 51, 61, 71, VP and others have a clip screw that screws into the inner cap from the outside, which also holds the clip on.

 

Inner caps can often be made quite easily. They should seal well against the shoulder of the section, should be long enough that the nib does not hit the inside end, and wide enough that the shoulders of the nib do not come in contact with the inner wall of the inner cap. If the pen is a lever pen, the length should be adjusted as necessary so that the clip lines up with the lever when the cap is closed.

 

Many lower end pens are simply a tube with a flat on one side to make room for the clip. Better inner caps have a closed end, which does a better job of sealing the cap to keep the nib from drying out.

[mingus]

It depends on the pen and the manufacturer. In many cases, the inner cap is simply a friction fit, especially on vintage pens. Adhesive is rarely if ever used since it would make it difficult to get the inner cap out when needed. Some pens however have the inner cap that is held in by a screw. Many Italian pens like my Aurea and the Omas Tokyo use a pin on the top of the inner cap to hold the clip in place, with threads on the outside of the inner cap so it screws into the cap. Pelikans have the ring above the clip that holds it in, Parker 51, 61, 71, VP and others have a clip screw that screws into the inner cap from the outside, which also holds the clip on.

 

Inner caps can often be made quite easily. They should seal well against the shoulder of the section, should be long enough that the nib does not hit the inside end, and wide enough that the shoulders of the nib do not come in contact with the inner wall of the inner cap. If the pen is a lever pen, the length should be adjusted as necessary so that the clip lines up with the lever when the cap is closed.

 

Many lower end pens are simply a tube with a flat on one side to make room for the clip. Better inner caps have a closed end, which does a better job of sealing the cap to keep the nib from drying out.

 

Thanks so much for the thorough response!

 

A few more questions:

 

1. When using a pressure fit, do you know if there has to be a hole on the end of the cap for air to escape when inserting the inner cap?

2. When the inner cap is threaded, do you know if there is a socket (phillips, hex, flathead, etc.) on the interior of the insert to aid in inserting it?

[Ron Z]

Most of the time the cap itself is not that air tight, which is the primary reason for an inner cap. When the clip is mounted on the side of the cap they file a flat spot on one side so that the inner cap can slide past the clip as you push it in.

 

How the threaded inner cap was screwed in depends on the manufacturer. The Omas Tokyo for instance has a slot molded in the end for a screw driver. Others to not. The thread (as with the Aurea and Tokyo in particular) is a coarse left hand thread so that the inner cap tightens rather than unscrewing and coming loose, as the cap is removed from the pen.

 

Some manufacturers have an integrated inner cap. i.e. it is machined as a step in the cap against which the section tightens instead of having a separate piece. Parker did this with the Vacumatic line of pens. Look at the Parker Duofolds, both vintage and modern. The top of the cap is part of the inner cap, and screws into the cap from the outside.

 

I should add that some pens used a rivet to hold the clip on and the inner cap in. Parker did this with the 45 and Falcon pens, which makes it impossible to replace the clip. Waterman machined the inner cap in the cap, but then used a rivet to secure the clip on their Hundred Year later pens. Its a joy to try to replace a clip on these pens. I end up making a new "rivet" out of brass, gold plating it, and securing it from the inside with a screw.

 

The design of the inner cap is as varied as is the number of pen manufacturers