Buy my Books!

The Sketchnote Workbook is a fully-illustrated book and video, showing how to use sketchnotes in new ways, along with advanced tips and techniques.
Learn about and buy the book →
Download a FREE chapter →
Watch a FREE video sample →

The Sketchnote Handbook is a fully-illustrated book and video, designed to teach regular people how to create sketchnotes.
Learn about and buy the book →
Download a FREE chapter →

Mike Rohde (Color - Square)

ROHDESIGN is the website of designer Mike Rohde, who writes on design, sketching, drawing, sketchnotes, technology, travel, cycling, books & coffee.
Read more about Mike →

SIGN UP! Get the Rohdesign Newsletter.

« Rohdesign Weblog Chosen by the 9rules Network | Main | Congratulations to Alex Bendiken, Slashdot Redesign Winner! »

The Uniball Signo RT Gel mini Hack

In my creating a custom Moleskine planner post, I mentioned a Uniball Signo RT Gel 0.38mm pen, for both creating the planner and writing agenda and task items.

Initially I'd purchased a 4-pack of Pilot G2 mini 0.5mm pens for pocket-ability, but found the ink bled a bit too much through the thin Moleskine pages, so I picked up a 4 pack of Uniball Signo RT Gel 0.38mm pens. The thinner 0.38mm gel pens work well with Moleskine paper because the line is thin and quick drying.

This weekend I was looking at the Uniball Signo and G2 Mini, when I wondered if I could hack the Uniball 0.38mm refill to work in a G2 mini pen body. When I took the two pens apart, I realized it could be done, with a flick of a utility knife to trim the Signo's cartridge down to size.

In the spirit of DIY, I gave it a try. The G2 mini to Uniball Signo mini conversion worked so well, I've decided to to share the easy conversion process with other Uniball Signo fans out there, complete with photos:

Uniball vs G2 mini

1. Here you can see how the G2 mini and Uniballl Signo compare side by side. The G2 mini is about 4.5 inches long, compared to 5.5 inches for the Uniball Signo. For pocket-ability, that reduction of an inch means quite a bit — making the G2 mini well-suited for pockets.

Uniball vs G2 mini - Exploded

2. Next, I opened up the two pens to compare the length of the cartridges, and as you can see, the Uniball Signo is about 1 inch longer, but has room for trimming. I've noticed that new Uniball Signo cartridges have ink at or above the location you need to cut them down without creating a mess. The easiest way to remedy this is by drawing with the cartridge until the ink level drops enough that a slice is reasonable.


3. Using a utility knife , x-acto knife or other sharp instrument, trim the Uniball cartridge down to the same length as the G2 mini cartridge as shown in the photo above (see the dotted line). I've that the Uniball Signo cartridge uses a much thicker outer wall compared to the G2 mini, so the G2 may actually have close to the same volume of ink even though it looks like less.

Chopped Uniball Cartridge

4. Here you see the nicely sliced Uniball cartridge, ready for insertion into the G2 mini pen body. If you want to be non-wasteful, you can keep the G2 mini cartridges for backups, or use clear tape to adhere the chunk of Uniball cartridge you've sliced off to the top of the G2 mini cartridge, and use this in a standard G2 pen. The G2 plus clipped cartridge combo doesn't work in empty Uniball Signo pen bodies, because of the G2's nib.

The Uniball Signo RT Gel 0.38mm mini

5. Use your new Uniball Signo RT Gel 0.38mm mini pen, and enjoy! :-)

Related Links:
Moleskinerie by Armand Frasco
Recording Thoughts by Steve Duncan

Reader Comments (16)

Excellent. I am coming to loathe the splotchy G2 pens, preferring to use Parkel Gel refills instead.
May 31, 2006 | Unregistered CommenterAndy
Andy, dunno if the Parker refills will work or not -- but do check them out. You never know! :-)
May 31, 2006 | Unregistered CommenterMike Rohde
Hi Mike, very nice hack! What a coincidence, I almost bought a gel pen today, but before buying I asked to test it and found it bleed too much. Didn't like it :( So a started testing some other pens and end up getting a Stadler triplus fineliner (Dry Safe). Got a blue and a black one. I'm getting ready for my M experience ;-)
May 31, 2006 | Unregistered CommenterVladimir Campos
Where, oh where did you find the 0.38 RTs? I've been using them for a couple years and they are my absolute favorite pens. But I have not seen any for sale in the past eight months or so.

I am utterly desperate to find some.

(Vladimir -- try the Uniball gel pens. They lay a very clean line).
Slick. But don't you need some sort of plug on the Uniball cartridge like the G2 mini has? Or does the gel ink stay put and the plug isn't really needed?
June 1, 2006 | Unregistered CommenterGary
No plug is included on them stock � just some clear gel above the ink level, so that's one reason you need to draw the ink down enough to make the cut.

If you do cut at the ink line then it might be wise to cap the cartridge somehow... putty maybe. The G2 cartridge has a thinner wall so you can't steal the cap to use on the Uniball cartridge � it's too large.
June 1, 2006 | Unregistered CommenterMike Rohde
Evan, Check OfficeMax � that's where I got mine. Maybe they even sell them online?
June 1, 2006 | Unregistered CommenterMike Rohde



Never ordered from these guys, but it's at least a lead. :-)

BTW, the code for the black pens is SAN69034, Blue is SAN69035 and red is SAN69036 � those codes turn up all sorts of results on a Google search.
June 1, 2006 | Unregistered CommenterMike Rohde
Thanks everybody. Be careful: Uniball now uses the "Micro" designation for the 0.5 sized pen (maybe for both). That's what I keep finding when I look at the walls of pens. This happened about the same time the 1.0 and 0.8 "Bold" pens started appearing in large numbers.

I used to live right near an OfficeMax, and that was where I used to buy them. The (now) local Office Depot doesn't have them. When I hit two OfficeMaxes while traveling, neither carried them.
(As a side musing, the OfficeMax I got them from was on the West coast, while I am now on the East coast. They don't appear to be on their website.)
Good idea. Also, Pentel will not be making refills for the mini, considering it disposable. So, you have solved another problem.
June 6, 2006 | Unregistered CommenterFishken
I get mine from$1.50 each. Free shipping if you order a certain amount. I am not sure of the minimum order for free shipping, but I ordered 16 black and 8 red and shipping was free.

June 7, 2006 | Unregistered CommenterRick
Ok, just tried it. But be careful, if you cut that refill too short, you will have a very nasty mess on your hands, literally. ;-)

Also, I noticed the Pilot refill had a little cap in it. I wonder if the pen's design needs that as a surface to push against? I popped the cap off the Pilot refill and placed it in the Uniball refill after cutting it.

June 23, 2006 | Unregistered CommenterChris Meisenzahl
Chris, I did need to write with the refil a while to draw it down before cutting because yes, it would be a mess. :-)

I think if you draw down the inl level then the cap is not needed -- the Signo cartridge is thicker walled and works fine with the G2 mechanism. I couldn't get that G2 cap to fit the signo cartridge!
June 27, 2006 | Unregistered CommenterMike Rohde
I just discovered today that a Cross gel rollerball refill fits into a Pilot Dr. Grip with zero modification.
July 27, 2006 | Unregistered CommenterDave

I like my pens extra fine and small so I quicklytried your conversion out. It worked great but I don't really like the feel of the G-2 mini. The grip area is too high up for me. But I noticed while I was writing with the Uniball that I really liked its feel. So what I did is convert the full size Uniball down to the G-2 mini size by cutting out a section of the Uniball pen with a hobby saw. It came out great and I like it a lot better than the G-2 mini. One thing I did have to do is glue part of the refill, that I had cut off to fit the G-2 mini, back on to the refill. It was too short to work in the mini uniball. Also, when I was done glueing the pen back together, I noticed that the glue line detracted from the overall aesthetics of the pen. To fix this I took some black 6pt chartpak graphic tape and covered up the seam. It looks pretty good now and I will probably have to try this on some of the other pens I have lying around.Take care,Matt
July 30, 2006 | Unregistered CommenterMatt

PostPost a New Comment

Enter your information below to add a new comment.

My response is on my own website »
Author Email (optional):
Author URL (optional):
All HTML will be escaped. Hyperlinks will be created for URLs automatically.