Questions about flex nibs

September 9, 2006

I find I like flexible nibs.

I found that after I worked with my Palikan M800 and then with my Omas Paragon.They both have 18K nibs but the Omas is so much flexier and I truely enjoyed the feeling.So here are few questions:

1.What makes some nibs flexible and some rigid even though they are all made of the same material ? Is it their design ?

2.I read I think at R.Binders site that you can buy a flexible 14K nib and replace it with an original 18K nib on your Palikan pen.I thought that since gold is a soft metal an 18K nib will be flexier than a 14K one.How can you explain this ?

September 9, 2006

I will leave that explanation to one of our nib geniuses and just say that I enjoy writing with nibs with flex, I love that "spring," but I have yet to figure out how to get real variation out of my more flexy flexes. I think I'm just too chicken to really put pressure on it.

Someone should do a DVD showing how to get line variation from a flex. I would buy it.

September 9, 2006

Nib flexibility comes from (a) flexible material and (b ) a design that allows that material to flex without breaking. That design includes an outline shape that gives the right amount of support, and making the material thin enough in the appropriate places.

Flexible (in this sense) is not the same as soft metal. 24K gold is not usable at all for flexible nibs, because if you bend it it stays bent. It is just soft. When you add the right mix of other metals to it, however, you can create something springy that will work very well. The 18K alloy used currently by Pelikan doesn't spring very well, because it's too soft. The reason those nibs don't fail all the time is that they are relatively thick.

Their 14K nibs work much better for being made flexible. The people who modify them for more flex basically do strategic thinning of certain areas of the metal.

Edited September 9, 2006 by *david*

Some pen videos · September 9, 2006

Here is a list of relevant older threads/articles. I think it is about time to summarize them. Eventually...

https://www.fountainpennetwork.com/forum/in...wtopic=9617&hl=

https://www.fountainpennetwork.com/forum/in...st=0entry3791

https://www.fountainpennetwork.com/forum/in...t=0entry59256

https://www.fountainpennetwork.com/forum/in...ndpost&p=134610

http://www.pentrace.net/penbase/Data_Retur...icle.asp?id=418

September 9, 2006

Antonios,

What are the preferred alloys to mix with the gold for 'sping'? Reading the "how" on tempering the process is similar to Beryllium Copper tempering. I don't care about the exact ratios - just what metals as I am just plain curious and my manuals don't deal with gold alloys.

Ron

Some pen videos · September 11, 2006

Ron, the best references for gold alloys are:

E. Brepohl, "The Theory and Practice of Goldsmithing", German Edition in 1994 and Translation from BrynMorgen Press in 2001.

and

Allen S. McDonald and George H. Sistare, "The Metallurgy of Some Carat Gold Jewellery Alloys"

Part I: Coloured Gold Alloys, Gold Bulletin.Vol. 11, no. 3, pp. 66-73. July 1978

and

Part II: Nickel Containing White Gold Alloys, Gold Bulletin. Vol. 11, no. 4, pp. 128-131. Oct. 1978

Typically "best" 14K alloy have 58.5% Au (of course ), the rest is copper and silver. Brepohl's book has plenty of date for hardness, tensile strength, ductility and color for the ternary Au-Ag-Cu but I have not been able to find fatigue and fracture toughness data (that would require some expensive specimens). We can eyeball the effects of other elements, but I do not think that there has been an extensive and authoritative study of ultimate flex gold alloy. Nathan has been trying to do something like this but mostly based on his experience and intuition (i.e., as far as I know without using metallography and chemical analysis tools). My guess is that it is possible that the "best" alloys may be also a bit off 14K.

Finally, I have told many people, who asked me recently, that it is possible to develop an "optimum" gold alloy + nib shape, by applying "modern" metallurgy, mechanical testing, and finite element analysis, but such studies are expensive and out of reach from the most companies that make nibs (my rough estimate was about $300-400K). We also have to remember that even if a company would invest enough to find the "perfect" flex, I doubt that the typical consumer would be willing to pay a significant $ premium to get it The bulk of consumers want a "bullet-proof" nib which implies a stiff (or mildly soft) nib.

PS> As for tempering, it is similar to other metals, after hardening you heat the metal to a temperature so that you sacrifice a bit of strength for better ductility.

The cooking recipe (time and temperature) depends on the exact alloy, as it is solid diffusion and microstructural size related.

Edited September 11, 2006 by antoniosz

September 11, 2006

This was of interest to me:

http://www.hooverandstrong.com/mill/flatsheet_specs.htm

Look for spring gold.

Ron

September 11, 2006

I have little knowledge of gold alloys, but I can speak a bit on steels. Strange-but-true, all steels have the same Young's Modulus, that is, the ratio of applied stress to the resultant strain in the material's elastic range. What separates a "spring" steel from a soft steel or plain iron is its yield strength, the stress at which it permanently deforms and doesn't spring back to original shape. The yield strength can be increased by alloying, heat treating, and work hardening. As far as a nib, it probably matters little what the metal is as far as flex (tipping material aside). It mainly depends on what the yield strength is, how far it may flex before being permanently bent (or, for a very brittle metal, broken). The higher the yield strength, the thinner the nib can be made to give more flex without permament deformation. I would guess the best material for a flex nib in terms of cost-effective function would be a properly heat treated Martensitic stainless (for corrosion resistance) steel, or perhaps even a Bainitic stainless steel (trickier heat treatment, but lends itself to thin pieces such as nibs, and compared to tempered Martensite, a fine grain Bainite offers equivalent yield strength with much greater fracture toughness). However, phase transformations in steels offer a large customization palette, and I don't think that gold alloys offer that type of latitude. I would guess that simple work hardening is used quite a bit for gold alloy nibs, but I'm just guessing here. I certainly can't see how a gold nib can have any advantage over a well done and less costly stainless steel nib, except perhaps for sales hype.

Some pen videos · September 11, 2006

I have little knowledge of gold alloys, but I can speak a bit on steels. Strange-but-true, all steels have the same Young's Modulus, that is, the ratio of applied stress to the resultant strain in the material's elastic range. What separates a "spring" steel from a soft steel or plain iron is its yield strength, the stress at which it permanently deforms and doesn't spring back to original shape. The yield strength can be increased by alloying, heat treating, and work hardening. As far as a nib, it probably matters little what the metal is as far as flex (tipping material aside). It mainly depends on what the yield strength is, how far it may flex before being permanently bent (or, for a very brittle metal, broken). The higher the yield strength, the thinner the nib can be made to give more flex without permament deformation. I would guess the best material for a flex nib in terms of cost-effective function would be a properly heat treated Martensitic stainless (for corrosion resistance) steel, or perhaps even a Bainitic stainless steel (trickier heat treatment, but lends itself to thin pieces such as nibs, and compared to tempered Martensite, a fine grain Bainite offers equivalent yield strength with much greater fracture toughness). However, phase transformations in steels offer a large customization palette, and I don't think that gold alloys offer that type of latitude. I would guess that simple work hardening is used quite a bit for gold alloy nibs, but I'm just guessing here. I certainly can't see how a gold nib can have any advantage over a well done and less costly stainless steel nib, except perhaps for sales hype.

Before the discussion takes (as usual) a philosophical turn, let me preface it by saying that you can make a flex nib from any material...

Turkey feathers have been used for centuries Inexpensive flex dip nibs are still made of steel but they corrode easily...

Anyway, more to the point of your reply. Gold is not worse than steel. It is structurally competitative because,

yes steel has a higher strength but its modulus is about 2.2-2.5 times that of gold (~200GPa versus 80-90GPa).

Actually you can bring gold to quite high strengths (500-700MPa). So taking into account the lower modulus,

it is makes it even with the upper echelon of modern steels. Gold also has good ductility which implies toughness.

Moreover, the workability of the gold alloys is better (i.e. lower strength in the annealed condition)

than the corresponding stainless. Although this is not a major issue, it helps.

Also, without doubt, the long term corrosion resistance of the high karat gold alloys is superior to that of stainless.

Of course, does it really matter to the consumer if a stainless corrodes after, say, 50-100-200 years versus gold which might last for several milenia?

Incidentally, titanium because of its realtively low modulus might be even more interesting than steel. But the bottom line is that you are right the "sale hype"

or as I prefer to call it, the "cosmetic value" of gold gives it a major advantage in the market. The recent push to 18K

is nothing else but a justification to higher premiums. The market is small - so it needs the premiums in order for them to remain profitable.

Actually, we forget many times that maximum flex is relatively "useless" .

The "wow factor" is high but properly controlling a high flex nib requires very large letters and long strokes.

For most practically writing, a decent bouncy semiflex nib is more useful .

Regards,

az

PS> I am not familiar with bainitic stainless steels. Which alloy you have in mind?...

September 11, 2006

Yes, it's all a trade off between the Young's modulus, the yield strength (and/or fracture toughness), and corrosion resistance, and the easiest (cheapest) way to get there. Steels do have an advantage of hardening by heat treatment, whereas most other alternatives must rely on work hardening that is limited in its effect. I don't know that there are any standardized Bainitic steels, stainless or otherwise. A few custom swordmakers produce fine grain Bainitic blades by quenching the austenized steel in a heated salt bath to just above the Martensite transition temperature. The result is a hardness similar to a tempered Martensite, but with much greater fracture toughness. It's a tricky process that does not easily lend itself to mass production.

Edit:

Howard Clark is the swordsmith making the Baininte Japanese sword replicas. He uses L-6. He does have a Martensitic cutting edge over the Bainitic body. Here's a link if interested:

http://swordforum.com/summer99/howardclark.html

Edited September 11, 2006 by Nihontochicken

Some pen videos · September 12, 2006

Yes but L-6 is not stainless.

The reason I asked about "bainitic stainless" is that I don't think it exists.

My understanding is that with significant addition of chromium (needed to make the material stainless) the bainitic transformation temperature becomes lower than the martensitic transformatin temperature and bainite formation is not possible.

Disclaimer: I am only a mechanical engineer that pretends that understands metallurgy

Edited September 12, 2006 by antoniosz

September 12, 2006

Some have asserted that "nib creep" is worse with steel than gold? Is there any consensus on that point?

John

September 12, 2006

Yes but L-6 is not stainless. The reason I asked about "bainitic stainless" is that I don't think it exists. My understanding is that with significant addition of chromium (needed to make the material stainless) the bainitic transformation temperature becomes lower than the martensitic transformatin temperature and bainite formation is not possible.

You may be right, but please check your references. My understanding is the the bainitic transformation is possible, but since the TTT curve (or CCT curve if you prefer) is pushed so far to the right that many tens (perhaps hundreds?) of hours of soak time above Ms may be required to allow the bainite transformation to take place. I cannot find my old printed reference of TTT curves for various alloys. A Google search has been the usual exercise in frustration, whereas I imagine Paris Hilton's bra size or favorite snack would have proved immediate gratification, were I so inclined. After much too long a slog through the extraneous garbage, I finally found one single crappy TTT diagram for a martensitic stainless steel, namely 410. Here's the link, see page 133:

mse.iastate.edu/files/verhoeven/7-5.pdf

The plot is ambiguous as to the products at just above Ms, however. Since it is the standard curve, not a "wierdo", my GUESS would be bainite, if one could wait long enough! Additionally, I found a reference to austempering a 52100 steel (medium chromium steel, not "stainless" per se). Again, you may well be right, I haven't really delved that deeply into austempering stainless steels, and my old college notes are, alas, apparently somewhat astray and incomplete after thirty years of neglect.

September 12, 2006

Some have asserted that "nib creep" is worse with steel than gold? Is there any consensus on that point?

John

Well, that's different. I suspect that nib creep has more to do with how finely finished the surface is. I have a steel nib that has had some work done on it. Nib creep on the part that has been worked on, not on the rest of the nib.