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How to Adapt a Platinum Converter for Pocket Pens

(This page revised March 11, 2019)

Reference Info Index | Glossopedia  ]

Fountain pen
Fountain pen

The primary problem facing the would-be user of a 1960s or 1970s Japanese long/short “pocket pen” is finding an appropriate converter. A few of these pens can use existing converters; e.g., Pilot MYU and Elite S models accept either a CON-20 squeeze converter or a CON-40 piston converter. Most other pocket pens are not so accommodating. This article describes how to modify a Platinum converter so that it will work in Center, Kumiai, Morison, Platinum, Takara, and some Teikin pocket pens and will also yield the maximum possible ink capacity. A converter modified as described here will of course still work in full-length pens as well as in pocket pens. There might also be additional brands of pocket pens in which it will fit.

Tools Required

{f you don’t have a razor saw, buy a Zona or X-acto razor saw yesterday. Don’t try to fake it with an X-acto knife; the blood from your fingers would make a terrible mess.

Parts Required

Supplies Required

The Procedure

Start by disassembling the converter. Remove the bullet-shaped metal collar that holds the back end of the assembly together by unscrewing it. If any other parts came out of the clear plastic barrel when you removed the collar, push the knob into the collar from the back to separate them. If they stayed with the barrel, just pull the piston shaft to separate them. The parts are shown in this photo:

Parts, disassembled

Using a sharp X-acto knife, make a mark on the knob 0.689" (17.5 mm) from the flange at the front of the knob. Use a sharp razor saw to cut the knob to that length, as shown in the photo below.

Cut length for the knob

Use the knife to make a mark on the piston shaft 1.024" (26.0 mm) from the back surface of the soft plastic piston seal. Use the razor saw to cut the shaft to that length, as shown in the photo below.

Cut length for the piston shaft

Using a needle file or 600- or 1000-grit sandpaper, file or sand just enough to make the two cut ends flat and smooth. If you’re using sandpaper, you can do this most easily by laying the sandpaper on the work surface and rubbing the cut surface of the piston or knob on the sandpaper while holding the part with its other end pointed straight up.

Smooth and buff the sanded surfaces with the gray side of a pink-white-gray or black-white-gray MicroMesh buff stick, and use the white to soften the edges just a little. This step is not mandatory, but you will be happier when you fill the pen and see the professional-quality work you did.

Reassemble the converter. Insert the piston partway into the barrel, fit the small black plastic collar onto the shaft, screw the knob onto the shaft until it rests against the small collar, and screw the bullet-shaped metal collar firmly back into place on the barrel.

The Result

When you’re done, you will have a converter that looks like the modified one shown here (upper). Note that the piston shaft protrudes from the back of the knob approximately " (4 mm).

Platinum converters
The knob is cut to the longest dimension that will fit into the pen models with the least space for a converter, including Platinum. Do not cut the shaft shorter so that it will not protrude past the end of the knob. If you do, it will be too short to engage the knob when the piston is all the way down, and the converter will not work.

In the next photo, the piston has been adjusted so that the shaft is just even with the back end of the knob, moving the piston seal forward far enough that it can be seen in the barrel. This is the way the piston must be adjusted to fit into Platinum and other pens with very restricted space for a converter. When you fill the pen, fill it all the way and then turn the knob back until the protruding end of the piston shaft is flush with the end of the knob. Clean as usual before capping.

Platinum converter

Your modified converter should fit into most of the pocket pens listed in the first paragraph above, as illustrated by the Morison in the image below. (Some Center pens will accept an unmodified converter, but my collection includes more pens than just a Center, and yours probably does, too.)

Fountain pen

The Catch

As noted in the preceding section, this modification produces a converter that will fit the majority of pocket pens that use Platinum cartridges — but not all of them. Some pens, e.g., this cherry wood Platinum pen, have too little room in the barrel.

Fountain pen

For these pens, it’s possible to trim the knob (but never the piston shaft) even shorter. To fit this wooden pen, I trimmed the knob to a measurement of 14.5 mm. For a Teikin pen with a flippable nib, that was not enough. To fit that pen, I had to trim 0.125" (3.2 mm) off the end of the bullet-shaped metal collar using a lathe. This allowed me to cut the knob to a measurement of 0.445" (11.3 mm).

  1. Teikin jobbed its pocket pens from Pilot, Platinum, and Sailor. Converters modified by this procedure do not fit Teikin pens made by Pilot or Sailor.  Return

The information in this article is as accurate as possible, but you should not take it as absolutely authoritative or complete. If you have additions or corrections to this page, please consider sharing them with us to improve the accuracy of our information.

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