An Engineer Looks At Nibs And Flexibility

[Precise]

We read a lot about gold nibs being more flexible, but a steel nib can be just as

flexible as a gold nib, if it's thin.

 

Flex:

 

It's true that 18k gold metal is about half as stiff as steel. So for identical

dimensions an 18k gold nib is about twice as flexible as steel. But dimensions

are very important too.

 

For a given metal, the nib stiffness is proportional to width multiplied times the

cube of thickness. The cube here means than reducing thickness by only twenty percent will double the flexibility of the nib. In other words, a steel nib can have

the same flex as a gold nib, if it's 20% thinner.

 

Line width:

 

Furthermore, why do you want flexibility in a nib? If your answer is to increase the line width when you press, we need to consider the arch of the nib. The amount of spread is influenced by the amount of arch. You can approximate the arch with angles as indicated by the dashed lines in this sketch. The greater the arch, the greater the angle and thus the greater the separation as the nib flexes.

 

So, variable line width is determined by more than nib metal. Thickness and arch play a big role.

 

Durability:

 

Of course you want the nib to spring back to its original shape after you press

down. In this regard thinner steel is a better choice than thicker gold. There is

less danger of it taking a permanent bend.

 

So while we associate gold with quality and value, it's not always the best metal

for the job. Steel is obviously a better metal than gold for your car's springs. It

can be better for your nibs too, when properly designed.

Edited September 9, 2015 by Precise

[ac12]

I recall a few other factors:

• tempering of the gold
• different thickness of the nib from tip to back end

But yes, some of the best flex nibs are the steel dip pen nibs.

 

The issue then becomes corrosion. A FP nib is in constant contact with ink/water. A dip pen nib is wiped dry after each use.

Can they make a GOOD flexible stainless steel nib?

 

A car spring is a bad comparison. Simply from perspective of cost they would NEVER make a gold car spring, as the cost of the car would go up at least $20,000, more likely a LOT more.

Edited September 10, 2015 by ac12

[Algester]

Actually gold for a car suspension is... Very impractical gold is not sturdy enough to be used the way its not meant to be used not to mention economical value, maybe MB would one day make it out of glitz and glamour but I dont think companies like ferrari, lambourghini, Aston martin would be able to do it

If and ever if MB does go into luxury automobile

Edited September 10, 2015 by Algester

[Precise]

Incidentally, titanium is about the same stiffness as 18k gold. It also has superb corrosion resistance. Hence it's use in artificial knees, etc.

 

And of course, stainless steel can be gold plated for very little cost. It's not impervious to corrosion, but it does "stain less". With gold plating (or even titanium plating), it's essentially impervious to corrosion.

 

At any rate, my point was that a steel nib can be flexible.

 

Alan

[beanbag]

Which alloy and tempering of stainless steel, then?

[Precise]

Which alloy and tempering of stainless steel, then?

Sorry, but I don't understand your question?

Alan

[Precise]

Which alloy and tempering of stainless steel, then?

I don't understand the question, but I'd like to mention an interesting fact about heat treating and hardness.

 

The surprising thing about steel is that it has the same stiffness regardless of temper and hardness. But harder tempers will flex farther before taking a permanent set.

 

Alan

[beanbag]

Give an example of a stainless alloy that will do what you say and "flex more than gold".

[Andreas Weber]

Which alloy and tempering of stainless steel, then?

 

There's significantly less than 10% difference between stainless alloys and temper has next to no influence.

[Algester]

Incidentally, titanium is about the same stiffness as 18k gold. It also has superb corrosion resistance. Hence it's use in artificial knees, etc.

 

And of course, stainless steel can be gold plated for very little cost. It's not impervious to corrosion, but it does "stain less". With gold plating (or even titanium plating), it's essentially impervious to corrosion.

 

At any rate, my point was that a steel nib can be flexible.

 

Alan

well yeah Pilot did it through their Shiro nibs... but that was way a few months before and during WW2 (depending on when you count WW2 began)

[beanbag]

 

There's significantly less than 10% difference between stainless alloys and temper has next to no influence.

 

If you're referring to modulus of elasticity, that's one of the less important metrics for a flex nib.

[Andreas Weber]

 

If you're referring to modulus of elasticity, that's one of the less important metrics for a flex nib.

 

Exactly.

[Canopus]

With titanium there is also the issue that it apparently doesn't lend itself well to capillary constructions, but that is only anecdotal. I yet have to find a useful paper about wetting angles on metal surfaces and polymers; that would allow for an interesting comparison of potential materials.

 

A lot of people complain that titanium nibs do have feedback, frankly I think that is more due to the final work done, or better said being neglected, on the nib because of the intended role as a flex nib. Maybe it doesn't dampen vibrations as well as gold, I certainly notice a bit of difference from steel when comparing two rigid nails.

 

I know that PEI would make a wonderful feed because it's strong, chemically stable, hydrophilic and easy to process. The downside is that it has the glass transition temperature in the ballpark of the 200 degrees celsius... so heat-setting without a special rig would be unfeasible.

 

I would perhaps consider maraging steel for a steel nib. And if we want to go fancy maybe some sort of amorphous metal alloy, they supposedly make really good springs, but then manufacturing and fatigue-cycles may be an issue.

[Precise]

Give an example of a stainless alloy that will do what you say and "flex more than gold".

Please note that I did not say what you quote above.

 

I said that "18k gold metal is about half as stiff as steel"

 

But I also said that flex is proportional to the thickness cubed. So if a steel nib is 20% thinner than a gold nib (which is similar in other dimensions) it will have about the same flex.

 

Best,

Alan

Edited September 10, 2015 by Precise

[Precise]

 

If you're referring to modulus of elasticity, that's one of the less important metrics for a flex nib.

 

I think that modulus of elasticity is the most important property of a material. It should really be called modulus of inelasticity, because the higher the number the stiffer the material. Here is the modulus of elasticity of some materials.

 

Ordinary steel 30 million PSI

Stainless steel 28 million

18k gold, about 16 million

Titanium about 16 million

Aluminum 10.7 million

Typical thermoplastics about 0.4 million

Wood (parallel to grain) about 1.5 to 2 million

 

What does this mean?

Imagine a rod of steel which has a cross-sectional area of one square inch. If you apply one pound of tension or compression, its length will change by one part in 30 million.

 

And, as I've already mentioned, the temper or hardness of steel does not change its stiffness. It only changes the level at which it will take a permanent bend and not spring all the way back. Harder tempers can be flexed farther before they take a permanent bend.

Edited September 10, 2015 by Precise

[beanbag]

Modulus of elasticity is NOT important because you can compensate by thickness.

A large elastic region and fatigue resistance are important.

 

Still waiting for an example of a stainless alloy to be used in a "flex nib".

[Precise]

Modulus of elasticity is NOT important because you can compensate by thickness.

A large elastic region and fatigue resistance are important.

 

Still waiting for an example of a stainless alloy to be used in a "flex nib".

"Modulus of elasticity is NOT important because you can compensate by thickness."

This was the exact point of my original post. As I wrote, people think gold (which has a lower modulus) is necessary for flex, but you can achieve flex with a thin steel nib.

 

Still waiting for an example of a stainless alloy to be used in a "flex nib".

Do you want me to identify a specific alloy? I've not engineered pen nibs, but others have. However I would expect that any of the 300 series stainless steels (such as 316) would suffice. Although if I delved into it further, I'd probably prefer some alloys over others. Here are a few links to steel flex nibs:

http://www.gouletpens.com/noodlers-ahab-konrad-flex-nib/p/N18094

http://www.fountainpenrevolution.com/nibs.html

 

Best,

 

Alan

Edited September 10, 2015 by Precise

[ethernautrix]

I don't know from science, but I have a vintage Hardtmuth Studio with a vintage steel Artus nib that flexes nicely.

[Algester]

and the Shiro nibs does it too... but since flexies lost its fancy through the years Pilot no longer makes them as well...

http://estilofilos.blogspot.com/2014/12/war-time.html

I have yet to see one yet alone write with one

Edited September 11, 2015 by Algester

[Christopher Godfrey]

I fail to understand why this sort of conversation continues to be of interest: is the point that someone would like to manufacture a modern flexible nib -- or are we simply showing off our knowledge of metallurgy (apologies, Precise: not meant to offend or belittle you!)? The most obvious answer to <most> people's needs is a good vintage Waterman's nib -- or a nice Wahl, Conklin, some Pelikans, etcetera, etcetera...those were the days of <flex>.

 

Now, that video attached of the Esterbrook 356 doesn't move me in the slightest: can you <hear> the scratchiness of the steel on the paper? And see the splashes of red ink down near the capital letter L? Sorry; but no interest at all: I can write just like that with several of my 1930s Pelikans or Waterman's...

 

This conversation seems very repetitive to me: it comes up all the time, in one guise or another...

 

(I'm running for the door, with flak-proof helmet on my head!)

Edited September 11, 2015 by Christopher Godfrey