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Casein GF piston filler MB139 style


Hello fountain pen friends !
Below 2 pictures of a new GF piston filler in MB139 style that I've just finished.
My integrated compact "single stage "piston mechanism design features a piston stroke of 31mm, without a telescopic filler. 
( telescopic MB139 =32mm)
The fountain pen is made of casein, which is actually milk ! (with color dyes).
Already in the 20s and 30s of the last century - and maybe earlier - fountain pens were made from casein.
I've found the material at an Italian company that used /use it to make buttons for luxury clothing, and I thought it was wonderful.
However, the  casein sheet was only 13 mm thick, and I needed at least 18 mm square.
So I sawed 27 mm strips off the sheet and boiled the strips for 5 minutes.
Then I pressed them directly between my workbench clamp screw into square strips.( using a lot of elbow grease!)
They were drilled with center bores and turned to 17 mm diameter
However, when I turned the bars to a larger inside diameter, they became completely oval due to the remaining internal deformation stresses!
Logical looking at it afterwards , but frustrating!
After some consideration, I decided to install the 17 mm rods radially and axially fixed in an aluminum bushing.
So I made new square rods and turned them back to 17 mm.
And to make the casein stress-free from the inside as well, I drilled 5 mm through the rods, which fortunately didn't cause any oval deformation.
The bore of the aluminum bushing is 17.1mm, the length of the bushing is 0.2mm longer than the turned rod.
In the lengthwise bore I installed a brass rod of 5mm - perfect heat conductor at the inside - and the whole assembly was sealed with 2 brass washers and nuts.
Then boiled the assembly for an hour, let it cool down, removed the bushing & rod and went back to the the lathe...
Perfect, not a bit of deformation occurred!
This is the hardest plastic I have ever worked with, very hard and probably brittle, hence not very resistant when dropping....
Since casein supposedly absorbs water easily, I polished a disc, put it in boiling water and let it sit for 5 days.
 I was happy to see he surface remained as hard and shiny as before.
Then into an inkwell for 3 days, very slight darkening but smooth and hard as before.
I suspect the manufacturer has made a special casein composition, clothes also need to be washed!
All's well that ends well, such a challenge keeps me vital and…young!
Please note that this pen remains in my personal collection, hence not for sale...
Greetings from sunny Flanders !

Giuseppe Tubi:
Bel lavoro. Complimenti vivissimi.


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