Step less barrel construction

[PatrickR]

I am going to work on a prototype step less. This seems to be the only way to make a pen as slim as I would like and they look sleeker and feel better in the hand. it would appear fairly straight forward. I know the cap will have to stop on the section, requiring a little alteration of the section and accurate drilling depth.

Any thoughts or pitfalls of going this route? Why is it so much less common than using a step for the stop?

Side note - the esterbrook I have that is made like this is a very small FP, lever filler but most notably to me the section is a slip fit. Which makes me wonder why the FP we make are always have threaded sections, slip fit is simple and makes a much thicker, stronger interface.

 

[duncsuss]

I like step-less barrels much better than stepped.

No adjustment to the section is necessary - you just have to drill the cap in such a way there's an internal ledge which hits the front of the section before the barrel threads bottom out. Draw it out on graph paper and you'll see how easy it is.

 

[Valleyboy]

It's fairly straightforward to do, exactly as you describe with end of the section registering against a lip inside the cap.

Just a couple of things to consider. One thing that I think is a worthwhile consideration when you design it is to have a fixed number of cap rotations to close the pen on each one you make. So as you say accurate depth drilling or boring is important. In my case I favour 1.5 turns and this is the same on my stepped and step-less models. It's one of the first things I look for when I pick up a pen.

Also if you want the cap to post then the location of that lip and the shape of your barrel-end potentially comes into play especially if you don't want the cap threads to grip on the end of the pen. (Or just make it non-postable).

I hadn't thought of a slip fit section until you mentioned it and can see why it would be beneficial, especially in narrower pens. I am glad I read this as you may have given me the answer to a small problem I have.

Cheers
Ash

 

[jalbert]

Side note - the esterbrook I have that is made like this is a very small FP, lever filler but most notably to me the section is a slip fit. Which makes me wonder why the FP we make are always have threaded sections, slip fit is simple and makes a much thicker, stronger interface.

modern cartridge converter pens need to be taken apart for filling, whereas the old esterbrooks and other sac fillers did not. Repeatedly removing a friction fit section is going to wear down the fit, requiring shellac to keep it in place.

 

[darrin1200]

One thing to watch, with the section stop, is to make the lip flat. I found that the angle, from a to pointy drill bit, can cause it to bind a little.

A slip fit, without the right design, may actually act as a vacuum when opening. Causing ink to be drawn through the nib when it's pulled off.

Rather than a slip fit, for a seal, you could use a replaceable o-ring in the cap. Cutting the groove for the o-ring can be tricky though.

I keep meaning to try a thin pen. Good luck with it.

 

[Darrin]

One thing to watch, with the section stop, is to make the lip flat. I found that the angle, from a to pointy drill bit, can cause it to bind a little.

A slip fit, without the right design, may actually act as a vacuum when opening. Causing ink to be drawn through the nib when it's pulled off.

Rather than a slip fit, for a seal, you could use a replaceable o-ring in the cap. Cutting the groove for the o-ring can be tricky though.

I keep meaning to try a thin pen. Good luck with it.

If you are using a metal lathe, this can be achieved fairly accurately with a boring bar and grooving tool.

 

[PatrickR]

I like step-less barrels much better than stepped.

No adjustment to the section is necessary - you just have to drill the cap in such a way there's an internal ledge which hits the front of the section before the barrel threads bottom out. Draw it out on graph paper and you'll see how easy it is.

They look sleeker and cleaner, also a better hand feel, yet I don't see many examples on here being made.
the sections I have been making I think would need a little adjustment to make the end stronger and seat well against a stop.

 

[PatrickR]

modern cartridge converter pens need to be taken apart for filling, whereas the old esterbrooks and other sac fillers did not. Repeatedly removing a friction fit section is going to wear down the fit, requiring shellac to keep it in place.

I have thought of this and am considered making a threaded end cap to reduce the number of section removals

 

[PatrickR]

One thing to watch, with the section stop, is to make the lip flat. I found that the angle, from a to pointy drill bit, can cause it to bind a little.

A slip fit, without the right design, may actually act as a vacuum when opening. Causing ink to be drawn through the nib when it's pulled off.

Rather than a slip fit, for a seal, you could use a replaceable o-ring in the cap. Cutting the groove for the o-ring can be tricky though.

I keep meaning to try a thin pen. Good luck with it.

The example pen has a very small hole in the cap, above the threads and bellow the section stop to alleviate this issue. The cap is not slip fit (friction fit?). The section to barrel is.
this approach wouldn't have to be only for small pens. The barrel diameter can be the same as the dies that you have.
my sample esterbrook is a very small pen. Too small for me. 11mm dia and 113mm long.
I will be trying 12mm first.

 

[darrin1200]

The breather hole is a good idea. They have been used in caps for years to maintain pressure balance.

Friction fit sections in vintage pens, are normally "adhered" with shellac. But as mentioned they did not need constant removal to fill. A blind cap would be a good solution, especially if you made it long enough to use the converter without removing it. The downside of this design, is the difficulty of using a standard international cartridge, which is much shorter than the converter.

The question that arises from using threads the same diameter as the barrel, is the choice of where the step will be.
Generally, the step on the barrel is there to allow a smooth transition between cap and barrel when closed. Barrel and cap are the same diameter.
By removing the step on the barrel, you are forced to make the the cap 1.5-2mm bigger than the barrel.
This ends up being a personal preference of the client, and I think both camps are about the same size.

 

[PatrickR]

After gleaning this info I have completed my first one. The main things learned were to only thread the barrel as much as needed and to keep the section as short as possible. Both of them can lead to a long cap.
here is the prototype and cap mandrel that were used. The threaded cap top was used to determine the depth of the stop and will be used for any more that are 13mm. Honestly I will remake the mandrell as I think the tolerances can be better.

 

[darrin1200]

Looks good. What did you make the mandrel out of. I am currently remaking mine in brass. The tolerance on my cap mandrel is tight enough to cause suction pulling it off, LOL.

 

[PatrickR]

Looks good. What did you make the mandrel out of. I am currently remaking mine in brass. The tolerance on my cap mandrel is tight enough to cause suction pulling it off, LOL.

The mandrel is 12L14 ultra machinable steel. It contains lead so it cuts very smoothly.
that's how it needs to be but isn't I don't feel any resistance pushing the cap on or pulling it off. So too small. I'll be more careful with the next one.