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How to Repair a Sheaffer Vacuum-Fil Plunger Filler

(This page published October 1, 2020)

Reference Info Index | Glossopedia  ]


Sheaffer’s “Vacuum-Fil” plunger-filling pens, made from the mid-1930s to 1948, are excellent pens, As you would expect of Sheaffer products, they write well, they handle well, they look good, and they are durable and long lasting. The downside of collecting them if you use your pens, however, is that plunger filler. In the years since these pens were made, the fillers have mostly died due to the failure of some of the materials used. This article describes and illustrates one way to repair a plunger filler. I do not refer to this repair as a restoration because the material used for the plunger shaft seal is not the original white felt. Instead, I use an O-ring, which is not subject to the dryout problem that killed the original seals.

Tools Required

Parts Required

Supplies Required

As you follow the instructions in this page, refer to these diagrams of a typical open-nib Vacuum-Fil pen to identify the various parts:

Cutaway view of pen, with parts labeled
Plunger head

Disassembly, Cleaning, and Seal Removal

In order to repair the plunger mechanism, you must work at both ends of the pen; unlike the Vacumatic filler, the plunger system does not give you the possibility of working only from the back. Start by removing the blind cap. Sheaffer used three systems for attaching the blind cap to the shaft:

Despite what you might have read in various repair books (including Da Book), do not use an alcohol lamp or other open flame. Celluloid is highly flammable!
  1. In the simplest system, the shaft is simply screwed into the celluloid material of the blind cap. It is, however, secured by thread sealant, and you might need to apply careful heat to loosen it. This system was used on prewar pens (both Sheaffer’s and WASP branded) and on the wartime “TRIUMPH” model.

    If the shaft is stainless steel, as most of them are, you can grip it with a pair of serrated-jaw long-nosed pliers applied from the side so that the shaft will nestle between the serrations. You can then unscrew the blind cap with your fingers or a gripper square, applying gentle heat if needed. It should never be necessary to grip the shaft so fiercely that your pliers make marks in it; but if that should happen, you can sand them out by spinning the shaft against a piece of 2000-grit sandpaper held between your thumb and finger so that it wraps halfway around the shaft.

    If the shaft is black, then it is made of mild steel covered with a celluloid sheath, and you must not use a metal tool to grasp it. The soft jaws of your section pliers, if turned so that they grip the shaft crosswise, are often sufficient.

  2. The next system was used on Balance pens only. It also screws the shaft into the blind cap, but the blind cap is fitted with a fixed brass nut, inlaid into the celluloid. There is a brass nut on the shaft; when this nut is screwed tightly against the inlaid nut, the shaft is held solidly. The shaft nut has a pair of notches cut in its periphery, and removing it requires a matching tool. The first photo below shows the shaft nut being loosened using the custom-made tool that Sheaffer’s repair staff used in the Fort Madison factory. The example pen in most of this article’s photos is a Carmine Balance Craftsman, and its blind cap was attached using the second system, but the Sheaffer factory tool works on both second- and third-version blind caps. If you do not have the luxury of owning an authentic Sheaffer factory tool, you can purchase a pin spanner from Or, if you are handy with a Dremel, you can grind your own tool from a screwdriver as shown in the second photo below.

    Loosening the shaft nut
    Homemade tool

    Once the shaft nut is loose, you can simply unscrew the shaft the rest of the way. Remove the nut and set it aside. This photo shows the blind cap, the nut, and the shaft after disassembly; the nut screws onto the shaft with its notched, flanged side first.

    Back end of a Balance
  3. The final system was used on postwar pens only. It also uses a nut, but this time the nut is threaded on its exterior and has a plain hole in its middle to allow the shaft to pass through. The blind cap is loose enough to wobble and free to turn about the shaft. A screwdriver slot runs across the exposed face of the nut, but because the shaft is in the middle, removing the nut requires a special tool. Sheaffer’s factory tool works for both this and the notched nut of the second system. offers two different tools for the nut in this system because Sheaffer made some of these pens with a nut having a slot that is 0.061" (1.55 mm) wide and some with a nut having a slot only only 0.036" (0.914 mm) wide. You can determine which tool you need by attempting to insert the back end of a drill from No 56 (0.0465"/1.18 mm) to No 53 (0.0595"/1.51 mm) into the slot. (Drills all the way down to No 63 should nominally work, but it’s possible that the slot is the narrower size but has been enlarged by an earlier worker, so we give ourselves room for a little slop in the slot’s width.)

    Unscrew the nut completely from the blind cap and set the blind cap aside. Unscrew the mushroom-shaped celluloid cap from the end of the shaft by applying gentle heat; the cap is secured with thread sealant, but you can turn it with your fingers once it is warm enough to soften the sealant. Now you can slide the aluminum nut off the shaft. Set the nut and cap aside. (Reinstalling them temporarily into the blind cap is a good way to reduce the likelihood of their going astray.)

    Back end of a postwar Crest

If you have a black shaft and the celluloid shows any significant bumps or roughness, that is an indication that the steel underneath is corroded, and it would be a good idea to seek a replacement shaft, preferably a stainless one unless you are going for an absolutely original appearance. Make sure that the unthreaded area of your replacement is exactly the same length as the original.

The length of the plunger shaft is critical to the correct functioning of the filler, and Sheaffer produced pens of different sizes, requiring 11 different shaft lengths over the course of 14 or 15 years.

If your pen is a postwar model with a Visulated section and a fully opaque barrel, the barrel is only a shell that screws onto the filler unit, and you should unscrew the barrel and set it aside so that you can work directly with the filler unit. In earlier models with transparency in the barrel, the barrel is an integral part of the filler.

The next step is to remove the gripping section (if a Balance) or the nib unit (wartime “TRIUMPH” and postwar models).

Do not use two section pliers, one on the barrel and one on the section or nib unit. The barrel is thinner just past the joint to allow ink to pass around the plunger head, and because heat is required to soften the thread sealant at this joint, it is easy to squeeze a section plier too tightly and distort the barrel.

Note that there is a projection on the back of the feed. In Balance models, this projection will be the end of the center feed, bent slightly to one side and shaped to make a ramp, as shown in the photo below. In later models, it will be an extension of one side of the feed. This projection is there to push the front of the plunger slightly sideways as the blind cap is screwed down, in order that ink may pass the plunger head more easily when the pen is in use. Do not remove or break the projection.

Nib and section, disassembled

You can now remove the plunger through the front of the pen. Push it from the back as far as you can push it, and then use a length of coat hanger wire to push it the rest of the way out. If it cannot pass the threads at the front of the barrel, stand the barrel up over an appropriately sized hole in a nib knockout block and drive the plunger down using a length of coat hanger wire and a light mallet.

Removing the Original Packing

The method for replacing the seal that is explained in this article is similar to the “standard” method that you can find on several other sites. It is more straightforward and less costly than that method, however, because it does not require the installation and solvent-welding of a plastic washer to retain the O-ring and because you can make many of the tools that you would otherwise have to buy. This method was originally devised by Nathan Tardif; in the intervening years it has undergone several improvements over Nathan‘s version.

Removing the original packing is easiest if you have a lathe, and I shall describe that process first.

Regardless of which drilling method we used, we did it with an “undersize” drill, and we did not remove all traces of the felt packing. Frequently stuck to the inside of the packing cup, it will need to be dug out in a way that does not scratch or scar the bore of the packing cup. For this purpose, you need a set of tools that you have modified from ordinary dental picks like the tools in these two photos. The second photo is a close-up of the tips of the tools so that you can see better how they are shaped.


The top tool in the first photo (middle in the second photo) is for scraping longitudinally. The middle tool in the first photo (bottom in the second) is for scraping radially. The third tool is an ordinary small probe with its tip bent at a 90° angle.

Start by running the probe around the packing cavity through the hole in the back of the barrel. The drilling process sometimes leaves the back rubber packing washer in place right next to the back wall of the packing retainer, and you first need to dislodge the washer and remove it if it is there. You can then use the two scrapers alternately. With the longitudinal scraper, start at the very back of the cavity and scrape forward until you hit a stop. That stop is either a piece of the felt or what is left of the original packing retainer. You can figure out which it is by working in a different spot or by checking how far you can slide the longitudinal scraper. When the cavity is clean, you should be able to slide the scraper back and forth about " (~3 mm). Work all around and then use the radial scraper to go around the cavity, flattening the surface as it picks up any small bits of felt that remain. The cavity must be clean all around so that ink and air cannot escape between the cavity wall and the outside of the new seal.

After you have cleared away the remains of the old packing, clean the interior of the pen thoroughly with the tubing brush and water, pen flush, or Rapido-Eze. Dry with a twizzle made from a paper towel. This is also a good time to clean the nib unit or the nib and section with pen flush in order to clear old dried ink out of the feed.

Installing the New Seal

To install the new O-ring seal, you need a special tool. You can easily make it from a length of " brass tubing as listed under Tools Required above.

Pusher tool, showing both parts

Cut a length of the tubing that is a little longer than the longest barrel you will be working with. Deburr the ends. For the push rod, I used the handle of a cheap single-ended dental pick, but you could use an appropriate wood dowel or metal rod. I turned one end down to a diameter of about " (5.16 mm) for a little more than " (6.4 mm) to make sure it would fit through the " hole that was drilled in the packing retainer, and I ground the end surface of that end to a slight angle. This angle is important: it ensures that the pusher will cause the O-ring to tilt into position instead of just sitting there refusing to be crushed.

Holding the O-ring with tweezers, dab a little silicone grease all around the outside and into the center hole. Don’t be stingy, but don't bury the O-ring, either.

Greasing the O-ring

Still using the tweezers, insert the greased O-ring into one end of the brass tube.

O-ring in pusher

Insert the tube into the barrel with the O-ring at the end that goes in first, seating it all the way at the bottom of the barrel. Insert the push rod into the tube. Set the barrel down on your work surface so that it is standing up on its back end, and hold it in place while you tap gently with a jeweler’s hammer to push the O-ring out of the tube and into the packing cavity. Twist the push rod all the way around to push the O-ring all the way into the cavity, then remove the pusher tool. The flange that remains from drilling out the packing retainer will hold the O-ring securely in place.

Setting the O-ring

Rebuilding the Plunger Head

Except during World War II, Sheaffer produced plunger-fillers alongside lever-fillers in all models of its pens from about 1934 or ’35 until the introduction of the Touchdown in 1949. To accommodate the different barrel diameters: slender, standard (Balance only), and oversize (Balance only), there are three sizes of plunger head gaskets:


With the 1942 introduction of the “TRIUMPH” pen, Sheaffer eliminated the standard and oversize gaskets, using the slender gasket for all further plunger-filler designs. Plunger head gaskets are available from several dealers on the Internet.

The original plunger head gasket, even if it looks perfect and feels flexible, must be replaced due to the aging of the rubber. To remove it from the plunger, unscrew the cap-nut. Early production cap-nuts were made of hard rubber and can tolerate more heat than later ones, which are celluloid. Heat the cap-nut gently and try to unscrew it with your fingers. Like the section or the nib unit, the cap-nut is secured with thread sealant, and it might take several tries before it comes off. If the plunger has a black shaft, rust might be holding the parts together. If the cap-nut just won’t come off, you can use a pair of serrated-jaw long-nose pliers to encourage it. Do not squeeze any harder than is absolutely necessary; excess pressure will deform the cap-pnut, which has been heated and is therefore somewhat soft. Once you have broken the cap-nut loose, check it for deformation. If it is deformed, heat it again, gently. Hard rubber will reassume its original shape, and celluloid will try to do so. You might need to squeeze the cap-nut a little to push it back into shape. Now you can remove the cap-nut from the shaft.

Remove whatever remains of the gasket with your fingers or with the aid of a dental pick. As shown in this side view of a plunger head assembly without its gasket, there is a space of reduced diameter between the cap-nut and the hard washer (sometimes called a “mushroom”).

Plunger head without gasket

This space is ensured by the boss on the back of the cap-nut. The boss is exactly the right diameter to guide and secure the gasket. The photo here shows the parts of the plunger laid out ready for reasssembly. First, if the mushroom came off the shaft, replace it with the flat side toward the length of the shaft; the cupped side will be toward the threads.

Plunger parts

Using a dental nano-pick, apply a very small amount of softened thread sealant into the tapped hole on the end of the cap-nut.

Some reputable restorers use shellac instead of thread sealant on this joint and on the joint at the back of the shaft between the shaft itself and the celluloid cap in the “wobbly blind cap” version. Either adhesive will work fine.
Applying sealet to the cap-nut

Pick up the shaft and hold it with the mushroom upward. Lay the new gasket over the tip of the shaft onto the mushroom. Now start the cap-nut onto the shaft, making sure you do not cross-thread it. Apply a little heat to soften the thread sealant, and screw the cap-nut down all the way, making sure that the boss on the back of the cap-nut fits into the hole in the gasket. Tighten firmly with your fingers. You can see in this side view of a completely assembled plunger head that the concave front surface of the mushroom causes the gasket to assume a very slightly cupped shape.

Assembled plunger head

The cupped shape of the gasket allows it to slide upward in the barrel relatively easily so that ink or air can flow past it toward the nib; but when it is pushed downward, it makes a tight seal so that air cannot pass around it. This ensures that a strong partial vacuum will be built up behind the plunger head. When the gasket passes into the wider part of the barrel, the seal is broken, and outside air pressure can force ink into the barrel.


The first step in reassembly is to install the plunger by pulling it through the barrel from the back. You can purchase a tool for installing the plunger from, but I find that tool and its method of use overly complex. The alternative, if you have a lathe, is to make your own tool from a length of coat hanger wire that is the same diameter as the plunger shaft (0.082"/2.15 mm), or slightly smaller. My homemade plunger puller is 0.073" (1.87 mm) in diameter:

Plunger puller

To make the plunger puller, select a straight piece of the hanger wire about 4" (~100 mm) in length, and remove the paint. Flatten and deburr one end. In your lathe, use a No 1 center drill ("/1.19 mm) to make a start hole in the flattened end. With a No 55 drill (0.0520"/1.32 mm), drill " (12.7 mm) deep and tap " (~6.4 mm) deep with a 0-80 tap. Drill slowly and clear chips often. For alignment, tapping is also best done in the lathe. Rotate the chuck by hand, not under power, lest it turn too far too fast and jam, breaking the tap. Back the tap out and clear chips often. Grind the other end of the tool to a point that is roughly " (3.2 mm) long, and dull it so that it will not poke holes in the O-ring you use to replace the shaft seal in the barrel. Sand the ground area to smooth it, and polish the entire tool, leaving no roughness that might scratch or scrape either the barrel or the O-ring.

The following procedure describes the use of the homemade puller. If you have a Pentooling puller, adapt as needed.

Screw the plunger shaft into the tapped end of the puller. Apply a small amount of silicone grease to the exposed end of the plunger shaft. Insert the pointed end of the puller into the barrel from the front and guide the puller until it finds the hole in the O-ring. Push it through the hole as shown here, being careful not to let the greased area of the plunger shaft touch the barrel wall. Grease on the barrel wall will prevent the filler from working properly.

Puller pushed through O-ring

Pull the puller carefully until the plunger head enters the barrel. At about the same time, you might feel a slight resistance as the end of the plunger shaft hits the O-ring. Pull more firmly, and the plunger shaft will go through the O-ring. Continue pulling until the plunger shaft is partly or entirely extended out the back of the barrel. Unscrew the puller from the shaft.


Reinstall the blind cap by reversing the process for its removal. If the pen has a brass shaft nut, be sure to install the nut with the notched flange going onto the shaft first. Aluminum nuts go on with the slotted end first, and the celluloid cap should be secured to the shaft in the same manner as with the cap-nut at the other end of the shaft. Shown here is the usage of my homemade tool as it tightens the brass shaft nut in a Balance.

Homemade shaft nut tool in use

Push the plunger down until it snaps into the wider part of the barrel, being careful not to push the shaft back through the O-ring. Air can now flow from the outside all the way to the O-ring. Test the seal with the “tongue test”: suck on the open end of the barrel and then, while you're applying suction, stick the end of your tongue against the open end so that it sticks when you open your mouth. Waggle the pen around a little. If it gradually loosens and eventually comes off, there is a problem with your seal. This most frequently manifests as a leak around the outside of the O-ring due to inadequate removal of the felt packing. You will need to remove the plunger and the O-ring and take the necessary steps to get all of the packing out of there before you reinstall the O-ring and the plunger.

When you have verified that the shaft seal is good, withdraw the plunger again and push it down quickly. It should make a distinct pop when it escapes from the barrel into the wider area. If it does not do this, the problem is usually an improperly installed gasket. Remove the plunger and examine the gasket installation, adjusting it as necessary.

Once you have verified that both seals are good, you can button up the front end of the pen. Apply thread sealant to the threads on the section (Balance) or nib unit (all later models). This is most easily done by taking a little sealant on the end of a dental pick and heating it slightly so that it will flow onto the threads more easily and uniformly.

Applying thread sealant to the section

Start the section or nib unit into the front of the barrel.

Installing the section

Heat the thread sealant until it is liquid enough to begin flowing around the threads, and then screw the parts together firmly. If sealant escapes onto the outside, wipe off as much as will come, and then heat the surface of the pen gently so that you can wipe off the rest of the sealant. For aesthetics and to prevent foreign matter from sticking to the pen (or the pen from sticking to your hand), there should be no sealant remaining on the surface or in the threads.

Test the pen by filling it with water. Start with the plunger fully withdrawn to the back of the barrel. Fill a glass or bowl with enough water to cover at least all of the nib and half of the section. Immerse the nib and section. Push the plunger in briskly until it pops. (The sound will probably be more like a sharp click! or clack!). Hold the pen immersed for five seconds, and then take it out of the water. If the barrel has transparency, you can look through it toward a light. With the pen held vertically, nib downward, you will be able to see the water level. For pens with Visulated sections instead of barrel transparency, you cannot see the water level in the pen, but you can gauge how much water was in the pen by emptying it. If the amount of water the pen holds is satisfactory, you have finished the repair. If not, you will need to troubleshoot all the places where leaks can occur.

If both seals are installed and working properly, the barrel will fill almost instantly to or more of its total interior volume.


Seen any WASPs lately?


WASP was a sub-brand of Sheaffer, and it was the brand on which the company “field tested” its new plunger filler in 1934. Lessons learned from the WASPs in the field were applied, and Sheaffer-branded plunger-fillers appeared a year later.

There are subtle differences between Sheaffer and WASP fillers, but there’s nothing that will keep you from working on WASPs and enjoying the fruits of your labor afterward. Here‘s what to look for:

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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