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How to Repair the Seal in a Moore’s Non-Leakable Safety Pen

(This page published May 1, 2022)

Reference Info Index | Glossopedia  ]

Fountain pen
Fountain pen

The primary concern facing the would-be user of a Moore’s Non-Leakable Safety Pen like the No 1 Tourist shown above is that the cork shaft packing is likely to have dried out and shrunk with age, leaving the pen unable to hold ink. Replacing a dead cork in a Moore’s Non-Leakable is so easy that it could be considered the “gateway drug” (the first step) to becoming a master at repairing the packings in other retractable safety pens and also in Japanese eyedropper-filling pens.

Tools Required

Parts Required

Supplies Required

As you follow the instructions in this page, refer to these diagrams to identify the various parts. (The cap normally posts on the operating knob; as shown in the lower view here, it has been unposted for easier identification of the parts that you will remove.)

Fountain pen
Fountain pen

Disassembly and Cleaning

First, remove the cap.

Because Moore’s Non-Leakable Safety Pen does not require the user to unscrew its operating knob, all threaded joints in the pen have an ordinary right-hand thread.

The slide is screwed onto the plunger knob and tightened without adhesive. In most cases, you can simply use your bare hands, perhaps with the assistance of a rubber gripper square, to unscrew it and slip it off the front of the barrel. If it is stuck, a very little bit of heat from the heat gun, applied to the slide but not the knob, should loosen the joint.

Removing the slide
Never use section pliers to grip the slide! It is fragile, it has no internal support when the pen is retracted, and you can very easily crush it.

If the slide still won’t come loose, it is probably ink locked. Use an eyedropper to fill the pen with water. Holding the pen with the nib upward, work the mechanism back and forth repeatedly to encourage the water to sneak past the dead seal. Eventually enough water (more is better) will accumulate in the bottom of the slide to penetrate the dried ink. This might take several hours; be prepared to leave the pen overnight. If this does not loosen the joint, you will have to soak the pen. Prop the pen up in a narrow glass or similar container and soak just the back end in cold water. Check frequently; as soon as the joint loosens, dry the pen and remove the slide.

The shaft (labeled Nib Carrier/Feed in the diagram above) is screwed relatively firmly into the knob. Heat that joint a little, and you should be able to unscrew it.

Removing the knob

Now you can push the nib/feed/nib carrier assembly far enough into the pen that you can grasp it and pull it out through the front of the pen.

Removing the shaft

Insert the point of the bench knife into the hole where the shaft passed through the packing retainer. Applying just enough pressure to keep the knife from slipping, unscrew the packing retainer.

Removing the packing retainer

Using the X-acto knife and the dental picks, carefully remove the cork shaft seal from the recess that the packing retainer was covering. In some instances, the cork will be dried up and shriveled, and it will simply fall out. (Don't count on this.) Do not dig or cut into the hard rubber while doing this!

Cleaning out the old cork

Using cold water and cotton swabs, clean the interior of the pen barrel, taking extra care to get everything out of the packing recess. Dry the interior of the barrel with a twizzle. During this process, the second packing retainer might come loose and fall out. Do not lose it!

Choosing and Installing the O-Rings

Use the caliper to measure the diameter of the shaft and the inside diameter of the threads in the packing recess. Especially in very small sizes, metric O-rings are produced in size increments that are much smaller than the increments for O-rings of imperial sizes, making it easier to zero in on the ideal fit. Depending on where you are located and what sizes you come up with, you might need to convert your measurements from metric to imperial or vice versa in order to come up with the part that will fit best.

From an O-ring vendor's website (e.g., The O-Ring Store LLC), choose the appropriate Buna-N O-ring (70 durometer). Follow the instructions in one of these two paragraphs:

Buy half a dozen O-rings; they're dirt cheap, shipping will cost you more than the parts will, and you never know when you (or a friend) might need another Moore’s Non-Leakable repaired.

Reinstall the inner packing retainer if it has fallen out. Coat the inside of the packing recess with silicone grease, but keep the grease away from the " (3 mm) nearest the opening so the packing retainer will be able to screw in and stay without slipping on the grease. Insert an O-ring into the recess and gently push it down as far as it will go, being careful not to squeeze grease up through the middle of the O-ring or up onto the area that must stay clean. A single O-ring is not sufficient to fill the recess, so add one or two more, such that the last one is far enough below the end of the barrel to allow for the packing retainer. (It can be farther down, but there must be at least enough space for the packing retainer to screw down flush with the end of the barrel.) The pen illustrated in this article uses three O-rings.

Installing the O-rings
The vast majority of Moore’s Non-Leakable pens will use the same O-rings as the MHR No 1 Tourist illustrated throughout this article, but it is always good to check. Pens that are larger in diameter, like the BCHR No 450 shown below compared with the No 1 Tourist, will need O-rings of a different size.

Moore's Non-Leakable Safety Pen Nº 450

Reinstall the packing retainer, and screw it down with the bench knife until it touches the O-rings. This might be farther into the barrel than it was originally placed; that is not an issue because nothing depends on the retainer’s exact location.

Be careful not to cross-thread the thin packing retainer as you are installing it. Cross-threading it will damage it so that it will probably no longer fit correctly.

If you are working on a larger model, you might find that there is not sufficient space for even two of the correctly sized O-rings. In this situation, use one of the correct O-rings and then add one of a smaller size (with the same ID but a thinner cross-section). Screw the packing retainer farther into the barrel as described above, and then screw it in about a quarter turn farther so that it compresses the O-rings slightly. This will increase the friction on the shaft.


Apply silicone grease around the shaft near, but not on, the threads. Insert the shaft assembly back into the pen, guiding it into the hole in the inner packing retainer. Screw it through the O-rings until it slides past the threaded part of the shaft, then pull it all the way. It will slide fairly easily as soon as the greased area reaches the O-rings. The presence of the shaft forces the outside of the O-ring against the threads in the packing recess. Together with the silicone grease, this will form a good seal, preventing ink from passing through the packing area.

Reinstall the plunger knob. If the plunger is too loose, remove the shaft assembly, screw the packing retainer down a little onto the O-rings, clean as much grease off the shaft threads as you can, and reassemble. This might take several trials until you get it so it's firm enough that the shaft won't slip but not so firm that it bends when you push it.

Finally, screw the slide back onto the plunger knob. The cross-sectional drawing below illustrates the positions of all the seal parts in an idealized pen that uses two O-rings.

Packing reassembled with two O-rings

Fill the pen and enjoy your handiwork. Because there is no overpressure or vacuum in a Moore’s Non-Leakable Safety Pen, it is highly unlikely that your repaired packing will leak. If it does, you will need to empty the pen and partially disassemble it far enough to remove the shaft so that you can tighten the packing retainer a little more. Reassemble and refill.

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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