Auto-advance Cartridge by Kayou

[Leonov]

The one and only @amjacobs7 helped me get one of these, and I rushed to fit the cartridge inside the Zento Signature pen body he himself got for me a few months ago — the extra space in the pen barrel was filled with a section from a dried Pilot Hi-Tec-C pen cartridge, which acted as a donor.

First impressions are nothing but amazing; in the world of executive EDC pencils, this simple trick might prove a game-changer; my next step is to compare the Zento-pencil combination with a Kerry and a Zombow Zoom “Superpen” which seem to have similar vibes, and are generally what I consider “standard unit of measurements” for EDC pencils — but I think I already see where this will end.

As a cool byproduct of this transformation, the original Zento cartridge ended in a Porsche-Design Titanium pen originally designed to work with fineliner tips, and the results are, again, spectacular, as if that cartridge had been designed specifically with the PD use-case in mind. Serendipitous star alignments, really.

[amjacobs7]

[Alan]

That’s what might be called a visual tautology.

[Gunther]

@Alan Conceived by the Department of Redundancy Department.

[Alan]

You mean the DoRD Dept?

[metal_punching_grip]

They could have added “wide grip”

[First_Sail]

What is this, it is real?

[amjacobs7]

HMM Plummet pen. I am working on adapting the Kayou mechanism.

[Gunther]

Yes, exactly!

[metal_punching_grip]

Let me share with you my failure of my week-end:

@drifand

The package comes with 90mm long leads, and they also feed one-way through a small hole in the back of the cartridge. It takes 1 piece of lead at a time… welcome back to the user experience of the very first generation of knock pencils!!

I tried to improve the Zento-Kayou by drilling a hole at the end hoping that I could refill the lead without disassembling the pen each time. The body is plastic so it was easy…

… unfortunately it doesn’t work. The lead falls in the cartridge but doesn’t engage if you don’t push it all the way in^[1]. Opening the pen is still required to refill lead. Oh well, now I have a Zento Signature with a hole (it was already quite worn when I got it so I’m not terribly sorry about this).

However, there is a silver lining. Along the way I found that the front grip had a little wobble so I investigated and managed to disassemble it:

The nose cone attaches to the metal core and holds the grip and the silver ring in place.

Tightening the cone while holding the rear thread solved my wobble problem.

Regarding the materials used:

• the core is chromed metal (non-magnetic, probably brass, maybe one day I’ll scratch the coating to be sure)

• the ring is probably steel (it’s the part that attracts the magnet in the cap)

• the grip is some hard plastic/composite, probably the same as the rear body

• the nose cone is painted brass (the golden colour is visible in the unpainted inside)

So at least I’ve learned something.

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1. I guess that using standard 60 mm lead (once the provided 90 mm ones run out) will probably require a second lead to push the first in ↩︎

[speedfreek]

@metal_punching_grip

the grip is some hard plastic/composite, probably the same as the rear body

That looks incredibly easy to make on a lathe in whichever material you’d want…

@metal_punching_grip

The lead falls in the cartridge but doesn’t engage if you don’t push it all the way in .

If you have a long stick, thin enough to go through the hole, you can load it without opening it.

And if that stick happens to be the right length and end with a ”head” you can use it as a cap for the hole.

If it also happens to be long enough to push a 60mm lead into the mechanism and thin enough to go into the lead sleeve you can use your favourite lead and clear jams too.

This, but made to fit your needs.

[ulfesharpe]

@amjacobs7

HMM Plummet pen

Wait a second — this is you?

[amjacobs7]

I am me. That is my pen.

[ulfesharpe]

Holy Toledo, so you produce pens/pencils?

[amjacobs7]

Ahahaha. I wish. That is HMM, a Taiwanese brand.

[ulfesharpe]

Oh okay… I got confused for a minute there.

[amjacobs7]

Thanks for all the info on the Zento!

[TomYang]

Using precision calipers, the Schmidt refill included with the HMM was found to be slightly thinner, measuring around 5.7 mm in diameter, while the Kayou refill is about 6.1 mm. Besides modifying the tip section, the refill body itself also needs to be carefully sanded down.

The plastic used in the Kayou refill is surprisingly hard, making it quite challenging to modify. The process requires a combination of shaving with a hobby knife and sanding, but achieving a perfect fit inside the HMM ballpoint body is still a little difficult.

For now, forcing the Kayou refill directly into the HMM body is not the ideal solution, even though it would be the quickest method. The HMM modification will be paused until more Kayou refills are available, allowing further testing with different tools and a cleaner modification approach.

With some model-making tools available, the process has gone fairly smoothly so far. The fun of DIY is honestly priceless, and this turned into a very satisfying afternoon project.

One challenge worth mentioning is the tolerance issue during the Kayou refill modification. After testing it in several different ballpoint pens, the biggest difficulty is securing the refill properly. Other than designing a custom resin-printed adapter, finding an effective way to eliminate the slight movement and make the conversion feel more solid and reliable remains the main challenge.

I also ordered another box of Kayou refills, so I’ll continue experimenting once they arrive.

For now, I temporarily converted my Pelikan P360 into a mechanical pencil. It is honestly way too much fun. The spring tension of the Kayou mechanism is a little softer, so there is a slight hesitation when pressing down. It takes some time to get used to, but I think I’ll adapt with more use.

I also have another one, a STAEDTLER CONCRETE converted using a Parker Jotter MP mechanism. This one wasn’t modified by me personally. When I have more free time, let’s see if we can find a better solution together. The main issue is that the internal spring can’t be removed, so the CONCRETE push button currently sits too high.

I would really like to try shortening the internal spring or replacing it with a shorter, stiffer one to improve the mechanism.