If you have ever used a fountain pen, you know they write in a variety of fashions. Some have firm nibs, they write clean crisp lines while others have flexible nibs, their lines vary in width as the letter is laid down. This is normally attributed to the nib material (gold, steel, titanium, or some alloy), and the width of the tip (fine, medium, broad, etc). However, there are additional factors, time to grab a pen and your high school geometry books.
The nib’s essential functions:
- Transport of ink
- Regulate ink flow
- Start and stop ink flow
- Vary the line width/style based on the writing
The four essential functions are to control by these actions:
- Placing the tip of the nib on paper and lifting it
- Moving the nib across the paper at a varying speed
- Spreading the tines with varying writing pressure
The line-of-bending is at the back of the nib where the nib extends past the section, which means the tines would never separate when equal pressure is applied (the nib would bend at the section). To address these two things happen, 1) a slit is added to the nib (the breather hole merely allows air displacement and prevents the slit from well … continuing), 2) the nib is arched/bent along the line of the slit. As pressure from writing is applied, the slit widens.
Many contemporary nibs (Namiki or Lam for example) has an arched body around the feed which transitions to flat tines, so how do these nibs work?
As the nib angles inward to form the tines, the line-of-bending moves forward from the junction with the section to the breather hole where the slit ends (X-Y to b1). The bending line b2 will follow the shortest cross-section from the termination of the slit (at the air hole) to the outer edge of the tine.
The red lines illustrate where the bend line is achieved when pressure is applied to the nib. The bend lines b2 enclose an angle with the line of bending b1. As the angle between b1 and b2 increases, together with the flatness of the tines, the nib becomes more responsive to writing pressure and variations. Sounds like a flex-nib to me.
The degree of tine separation depends on several parameters:
- The angle of the longitudinal bend (along the axis) of the nib
- The angle between the lines of bending
- The length of the slit within the area where the tines are able to bend
- The profile of the tines (thickness and curvature)
A standard nib deflects under normal writing pressure for only a few tenths of a millimeter. In material physics, deflects is a “deformation within the range of elasticity.” After the pressure is taken off the nib, it will return to its original shape, unless too much pressure is applied resulting in the extension of the tines beyond the normal range of elasticity, resulting in a permanent distortion. The nib will not return to its original shape and in layman’s terms is “jacked up,” and rendered useless.
For an amazing dissertation on fountain pen engineering, I recommend the following links, without which this post would not be possible.
- Fountain Pen Design; Nib Mechanics
- Fountain Pen Design; Flex Nibs Technology
- Fountain Pen Design; Flex Nibs More Technology
6 thoughts on “Pen Nibs, More than Just A Type, its Geometry”
I stumbled across your incredible Chronicles blog while looking for information regarding a Chronicle Fountain pen, dated May 28, 1912, that my dad gave me years ago. I want to actually use it but need more information in how to proceed.
Would you be able to help? I am lost.
Bitsy, A Conklin Crescent pen with that patent date is made of hard rubber, DO NOT get it wet. I would recommend googling vintage pen repair services. There are lots of people who do this kind of stuff professionally – I am not one of them. It is not so difficult as to prevent a novice. I have a post during the summer of 2021 about restoration workflow. It covers the basics. Google and youtube will provide video guidance. Best of luck
Thank you so much! I have googled enough about fountain pen repair to know it’s way out of my purview! I appreciate your input.
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