Attempt At A Piston Filler

[jalbert]

Greetings all!

I am new to the kitless pen making game, as I switched from making kit pens a couple months ago. I had been turning kit pens for nearly a decade, but wanted a new challenge. Anyway, I have been fascinated for several weeks with the idea of making my own piston fill mechanism, so I finally bit the bullet and over the past few days I worked off and on to come up with some sort of homemade mechanism.

The pen itself is made from a Craft Supplies USA acrylic blank, which I don't really like that much, as it turned out to be more violet-pink than I would have liked. For that reason I used it for this pen, since it was more or less an experimental endeavor. The nib is a #5 Jowo fine.

The piston mechanism is machined out of aluminum, and is a pretty straightforward and simple design, consisting of the piston itself and a housing, which is bored and tapped to accept the threads of the piston. The finial on the back of the barrel screws off to provide access to the knob that moves the piston.

I am reasonably happy with the end result, as it functions thus far without any problems. A few things in retrospect that I would change are:

-Larger or more grippy knob

-Use a lower thread count for the piston, as it takes a LOT of turns to move the piston completely up or down

-Use aluminum for the threaded piece that connects the body and finial to the piston mechanism

- The overall shape of the pen and effort put into finishing

 

Since this was largely an exercise in engineering the mechanism, I didn't pay a lot of attention to design (shame on me!), so please don't judge me too harshly!

 

[fountainpagan]

Congratulations!!!!

 

Let me tell you: I love the design of the pen. Its the acrylic I don't like. But I am sure others will, don't worry.

It seems to me you have a great did done here.

Let us know when you will ne ready to sell you piston filler pens.

 

Again, well done.

[jalbert]

Thank you for the kind words!

I am glad we are in agreement on the color of the acrylic. It's always a gamble when ordering a color you haven't seen in person. I suppose the upside is that when you get a less than satisfactory color, you can use it to experiment with and not use the good stuff!

[fountainpagan]

I agree. It is better if you don't like the colour: less attachment to the pen, less pain if something goes wrong with the experiment

[PANDM]

That's great, even if the blank is not your favourite. I have been stumped to make a thread that won't be so fine for the piston thread, do they make small taps and dies with about 8-10tpi or does it need to be done on the lathe.

[jalbert]

That has stumped me as well...The thread on this piston is 1/4"x 20tpi which is too fine for my liking. My next step is to try something more coarse, like maybe an 8 tpi as you mentioned. So far I haven't been able to locate anything coarser than a 1/4 x 16 tpi die. Unfortunately I know nothing about threading on the lathe without using dies, so I'd need to do a substantial amount of reading before I attempt that.

[PANDM]

My lathe needs new half nuts so I suppose I will have to get them if that is the only way to get the thread I want and then have a few practice runs. If I can get an external thread then I can then use that to cut the internal thread, hopefully.

[Buster99]

Hello Jalbert,

 

I like the way you are proceeding, nice to see it is a piston filler.

I do however question whether aluminum will hold up to some of the more acidic inks, using plastic parts may be safer and more durable but I am not certain of this.

 

You may want to read up on making threads on a lathe.

That is for metal lathes with threading capability, not for wood lathes! It will enable you to make your own threads quite simply and should solve any problems you may have of the need for overturning the knobs.

You should be able to choose a lower pitch or make a multi-thread, that will also greatly improve the way you screw on the pen's cap.

 

There are many articles on how to do all this, here on FPN and also on many external sites.

Using a metal lathe with threading capability also gives you the option to grind your own threading bits in a relatively easy way.

 

I don't know which type of lathe you are using so I hope this info is of some help.

 

HTH,

Marc

Edited July 23, 2015 by Buster99

[jalbert]

Thanks Marc! I didn't even think about ink acidity and aluminum. I don't know a lot about the finer points of fountain pens. I used aluminum mostly because I was worried about durability and didn't want to use plastic and risk breaking the small parts. I'm planning on trying out plastic though.

As far as lathes go, I have a benchtop Grizzly metal lathe. I definitely need to read up on using it for thread cutting. Thanks for the advice!

-John

[jj9ball]

That is awesome!!! I've been thinking a little myself about trying such an animal. I would be interested to see how the housing connects to the threaded nut that screws into the plastic part of the pen. I see you have an oring near the nut. Does it just slide in and stop on the oring? Also how did you come up with the proper size oring vs the size of the plunger? or to put it another way... How did you decide how hard to stretch the oring? Very cool pen. I can't wait to see the 2.0 version.

[jalbert]

Thanks for the kind words!

 

That is awesome!!! I've been thinking a little myself about trying such an animal. I would be interested to see how the housing connects to the threaded nut that screws into the plastic part of the pen.

 

Basically the housing that connects the mechanism and the removable end cap to the body is just screwed in tightly. I used pliers with tape wrapped around the jaws to tighten the housing down into the barrel. Yea, I know, not very professional That is one of the design aspects I am working on with version 2.0, which is in the works currently.

 

 

I see you have an oring near the nut. Does it just slide in and stop on the oring? Also how did you come up with the proper size oring vs the size of the plunger? or to put it another way... How did you decide how hard to stretch the oring? Very cool pen. I can't wait to see the 2.0 version.

The o-ring on the back end of the mechanism just serves to keep the housing in place so that the mechanism is captive and can't be pulled out of the pen. Ideally I wanted to use a small aluminum collar with a set screw to accomplish this, but I didn't have a small tap and die to thread the collar for a set screw. However I picked up a small metric tap and die set yesterday, so the next version will have a collar instead!

As far as O-Ring sizing went, I used my ultra high tech method of trial and error. The internal diameter of the filling chamber is 10.25mm, so I basically just turned the plunger slightly smaller, like 9mm I think, and turned a small groove in it for the O-Ring. I then picked an O-Ring that was slightly larger than the chamber diameter when stretched over the groove of the plunger, send I gradually deepened the O-Ring groove until I achieved a good seal with the filling chamber.

[Algester]

here's some of the things I know about piston and DIYness if your afraid about ink and the aluminum touching there's a solution for that it involves buying a syringe and using the gasket from the syringe to be used as a seal for the piston rod (you may have to mill the rod to fit the seal) but the way I see your piston rod has a lot of threads... so I'm not sure if that will be a good idea either

Edited July 26, 2015 by Algester

[Oruc Gazi Kutluer]

Using multiteeth taps would be more effective than enlarging the thread number.. I know metric system so M5 x 1.0mm x 3 threads will work fine I think..

 

Rest is great