Press fit caps ???

[PenWorks]

I have been experimenting with press fit caps. I think a good press fit cap solves a problem we experience to often. Customers pull when they should twist, or twist when they should pull[xx(]

Here is 3 different materials I have tried this with, A steel bushing, resin & ebonit. They all work! But it is time consuming and hand fitting. Bruce brought this up just now. If there is a way to mass produce the right press fitting it would be nice.

The ebonite material works the best using the press fit method, as the material being a rubber base(I think) gives it a little stretch and feels good mating with the nickle bushing.

Just some food for thought. What do you think Bruce? There has to be an easier way than by hand fitting. Also, there is a pic of the sterling silver clips I am working on [8D]

 

[Fangar]

That's a neat idea, but like you said very time consuming. I am suprised that more manufacturers don't make nice press fits.

James

 

[JimGo]

Anthony,
I don't write with, nor am I familiar with, fountain pens. So, with that MAJOR qualifier, doesn't a fountain pen need an air-tight seal to keep the nib from drying out, and to keep it from leaking (e.g., providing positive pressure inside the cap, to keep the ink inside the pen)? In that case, isn't a threaded end a better choice, since you get a tighter, more positive seal?

 

[PenWorks]

Jim, I think the press fit cap is a better seal. Haven't water tested it though. If your FP leaks that much through the cap, I would say you have issues with the feeder and not the cap. []

 

[driften]

Good idea Anthony! I do like the idea of screw caps but I think press fit caps have their place! Just like on the Safari.

 

[RussFairfield]

For what it's worth, I have watched a lot of people pick up a pen, and most of them will try to unscrew it first. That means making a pen that will not come apart when they try to take it apart.

Your design has solved that problem, while providing the tighter seal that is important to both a rollerball and fountain pen. Thanks for sharing.

 

[PenWorks]

The middle pen that has PenWorks on it, I have been using since I completed it. Everytime I uncap it, it writes, even after a day or two. The neck pen I made myself where I had to drill a hole in the cap for the jump ring, dries out in minutes. So a good seal does make a difference. I have to CA that hole shut and hope that solves the problem.

 

[JimGo]

Anthony, are you not using the threads on the ebonite pen? I wonder too, if you were to coat the inside of the cap with something like rubber cement (not thick, mind you), if that would give you a positive enough seat for a wood pen (and maybe help reinforce the wood, too).

 

[PenWorks]

Jim, if you look at the black painted ebonite pen, you will see it is threaded. Well it was a botched thread job, that's when I started tinkering with the press fit cap idea. I finally found a good use for the black CA Daniel sells [] Rubber cement might work, but you are going the way of hand fitting it. I was thinking on the lines of what was brought up last time we when we discussed threading. Some type of nylon or derlin bushing, something with a little flex to it.

 

[Randy_]

Seems to me that you are always going to have a "problem" with the press fit idea in wood pens because of their natural expansion and contraction of the material??? Might work with stabilized wood???

When you say "press fit" are you talking about using mating surfaces that are cylindrical in cross section or are you talking about cone shaped surfaces??

 

[PenWorks]

Randy, I have not done this in wood, only in man made material, The design is cylindrical in shape.

 

[wayneis]

Anthony I think that you are on to something, I think that press fitting is a great idea. I would think that maybe you would need to make at least one end a rubber like material or coated with some kind of rubber, like painting the inside of the cap with liquid rubber.

Wayne

 

[btboone]

I agree that a simple press fit is probably not the answer because it is so close tolerance and will likely wear and change over time. Something has to flex and hold. There are options with springs, plastics, or rubber. I see your flanges have just a slight bow, which might enable such a click. I've also seen slick systems with ball detents and others with magnets. Another option is to get a piece of spring steel wire and bend it from circular to a slightly triangle shape. It would sit in a groove and be able to flex enough to catch in a matching groove in the cap. The tough part is the undercut groove, which takes special tooling. Any type of cap holding device would be tough in wood. It does seem to work better with the tighter tolerances possible from plastics. Something else I'd like to experiment with (in my SPARE time) is a super high helix multi thread screw. It would have something like 10 starts and a 60 degree helix angle. They could even be cut on a taper to match a pen profile. On such a thing the movement to open the cap would be half pull and half twist, so isn't as likely to get ruined by someone doing the wrong motion.

 

[PenWorks]

Lamy uses allot of detents that are really nice, but very precise. I did a couple of proto types with the magnets, to time consuming, but unique.

 

[driften]

I wonder if a rubber O ring could help make a press fit?

 

[JimGo]

Bruce, a magnetic closure is an interesting idea. With some of the rare earth magnets, you could get pretty small and still have a very solid closing. If you put a thin ring of iron or another magnetic metal in the cap, and embed a magnet (or even two 180 degrees apart) in the appropriate mating surface of the pen, that might hold the cap on pretty well.

 

[driften]

Well.... the magnet could cause lots of problems. I can just see users erase credit cards and such from mishandling the pen. Also would it really provide an air tight cap? I think other methods might work better, but I am no expert!

 

[PenWorks]

I bought a bunch of rare earth magnets to make caps, from 1/32 and up. If you read the disclaimer, you think the guy would have a heart attack if he put the pen in his pocket and was wearing a Pace Maker [B)]

 

[jenamison]

It sounds funny, but actually those rare earth magnets are so strong that if placed just right and the mouth was in the right position, it might cause some issues. Those thangs are so dang strong. If your not careful they will pinch the crap out of your finger before you know it.

 

[btboone]

Then there's that annoying propensity for the magnet pen to pick up all the staples and paper clips from your desk as you write.[]

 

[woodscavenger]

Good point Bruce![] I wonder about the O-ring comment made earlier. That would be an easily replacable item if it ever wears out....

 

[btboone]

I looked at O-rings in an early version of one of my titanium pens. I didn't have room in there for an O-ring in that design. The smaller O-rings are 1/16" diameter, then you need material underneath to keep the body strong enough. I suppose it's no thicker than threads would be, but The cap on my first design was approaching too large without threads or O-rings. It can probably be done on a different design without issues. If the cap had a corresponding groove, it could serve as the snap device and the airtight seal.

 

[driften]

Originally posted by btboone
<br />If the cap had a corresponding groove, it could serve as the snap device and the airtight seal.

That is what I was thinking....

 

[jdavis]

nice idea.