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How to Restore the Wahl-Oxford Twist Filler

(This page published February 1, 2017)

Reference Info Index | Glossopedia  ]

Fountain pen
Fountain pen
Fountain pen

The Wahl-Oxford twist filler is an excellent, and interesting, pen. It is well made, and it has a filling mechanism whose complexity belies the pen’s lower-line position in Wahl’s product range. Nobody knows why the company built such a relatively costly filling system that it didn’t use in top-line models; but it’s easy to suppose that Wahl wanted to evaluate the design before launching it with the full force of the company’s brand-name reputation behind it. Given that this twist-filler variant is a multi-cycle design featuring an ink-view barrel, it might be that it was intended to be thrown into the ring against Waterman’s ink-Vue — but apparently it didn’t make the grade, and it was soon abandoned. Collectors now find Wahl-Oxford twist fillers in need of repair; the procedure outlined in this document was developed to fill that need.

Tools Required

Parts Required (see footnotes for more information)

Supplies Required

As you work through the procedure, refer to this photograph to identify the parts of the filler assembly:

Parts layout

Special Tools

Only one special tool is required for this project: a pin spanner to remove the nut that secures the forward end of the filler assembly. The wrench shown here was made from a paint can opener by bending the blade end straight with a pair of slip-joint pliers and grinding away the center of the blade to provide space for the threaded end of the filler’s nipple. A little of the outside edges also needs to be ground away so that the wrench will just slip easily into the pen’s barrel. Sand the ground edges to deburr them.


Disassembly and Cleaning

To prepare for disassembly, remove the blind cap and set it aside. Next, remove the section. The section screws into the barrel, and you will usually need gentle heat to soften the thread sealant. Heat the barrel adjacent to the section just until it’s not quite comfortable to touch with your lower lip, then use section pliers and a rubber gripper square (or two pairs of section pliers) in the normal way to unscrew the section. Set it aside, being careful not to break the hard rubber breather tube.

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!

The first step in disassembling the filler is to remove the twist knob and the aluminum bushing to which it is attached. The bushing is not screwed deadly tightly into the barrel, and it might come out without the application of heat. I find that the best way to grasp the barrel and the bushing is to use one pair of section pliers to grasp the barrel in the area where the forward end of the filler assembly is fitted, about halfway along then barrel. (This will ensure that you don’t crush the barrel if you have to apply significant force.) Then, with the other section pliers turned around backwards as shown here, grasp the metal bushing immediately adjacent to the end of the barrel and unscrew it.

Removing the knob and bushing
It is necessary to turn the second section pliers around because the grip of the jaws is slightly tapered. If the pliers are facing the usual way, they will be grasping the plastic knob instead of the metal bushing, and it is likely that you will break the knob as you try to turn the assembly.

If the bushing does not come loose relatively easily, heat the barrel immediately adjacent to the bushing, taking care as with the section end not to heat it too much, and then unscrew the bushing.

If the bushing still does not come loose, the pen might have suffered a sac rupture, and there might be dried ink in the threads. In this case, heat will not work, and it will be necessary to soak the barrel (as described below) with the bushing assembly still in place. If you have to do this, water will penetrate into the space between the bushing and the parts within it, and you will need to allow extra time for that water to evaporate.

Use your usual sac removal tools to remove any remains of the sac. Wahl used a short necked sac that was a very snug fit into the barrel, and parts of the sac are likely to be stuck to the barrel wall.

With both of its ends open and the sac’s remains removed, run the barrel for a five-minute cycle in your ultrasonic cleaner, using plain cool water. (If you do not have an ultrasonic cleaner, you can soak the barrel in plain water for about half an hour.) This step is designed to dissolve any dried ink that might prevent the forweard end of the filler assembly from coming apart.

Insert the special wrench into the front (externally threaded) end of the barrel, seat it gently against the filler nut, and turn gently counterclockwise until its two prongs slip into the notches in the nut. Applying sufficient pressure to keep the prongs from popping out of the notches, try to unscrew the hard rubber nut. This may take several attempts; try to apply the twisting force with enough control so that if the nut suddenly lets go, it simply become easy to turn instead of spinning wildly.

Excessive force at this point can destroy the nut, either scraping away the sides of the notches or actually splitting the nut. You can also damage the interior of the barrel by scraping it with the wrench, so control is essential.
Removing the nut

What Have We Here?

There are two types of barrels in these pens. So far as I have been able to determine, Type 1 barrels have no bands around the middle of the barrel, as shown in the parts layout above, and were used only for pocket pens. Type 2 barrels appear to have been used only in desk pens, and they have twin bands around the middle of the barrel as shown here:

Type 2 barrel

The foregoing said, I am not certain of this exact dichotomy, so you will need to examine the barrel. Check it internally from the front (externally threaded) end, using a bore light, to see whether you have a Type 1 barrel (celluloid washers and rubber seal, as shown in the parts layout above) or a Type 2 barrel (dividing wall that is solvent-welded to the barrel, as shown in the patent drawing below, with the wall colored pink and the barrel green). The nipple and nut, colored blue and violet respectively in the patent drawing, are the same in both versions. If you have a Type 2 barrel, skip to Disassembling a Type 2 Barrel.


Disassembling a Type 1 Barrel

Find a hole in the knockout block that the " tubing will just fit through. Insert the tubing into the front end of the barrel, and position the barrel over the hole you found in the knockout block. Gently hammer the tubing to drive the filler parts out of the barrel. If nothing moves, soak the barrel some more and try again. When the filler parts are free, separate them and see that you have all the pieces that are within the red dotted box in the layout above. The celluloid washer that was closer to the back (conical, unthreaded) end of the nipple is likely to have become conically distorted by the pressure of the sac. This is not a problem. Discard the seal. Skip to Salvaging the Sac Retainer.

Disassembling a Type 2 Barrel

With the nut out, the only part remaining to be removed from the barrel is the nipple. The easiest way to remove it will probably be to simply push it gently out the back end of the barrel with the punch, inserted from the front end.

Salvaging the Sac Retainer

Inside the aluminum bushing is an aluminum spindle. The sac is held into the “cup” on the end of the spindle by a small piece of celluloid (the sac retainer). The cup and the sac retainer are squarish in shape to prevent the sac and sac retainer from twisting inside the cup. Use the X-acto knife to chip any remaining bits of the sac out of the cup. As you are doing this, the sac retainer will be freed up, and you will be able to remove it. Be careful not to damage the sac retainer; you will need it to reassemble the pen. Shown here is the bushing assembly with the sac retainer still in place (left) and with the sac retainer removed (right):

Sac retainer location
The wall of the spindle cup is rather thin, and it is frequently also brittle. Be careful in chipping out the bits of the sac. If you apply excessive force, you can break out part of the cup.

Clean all parts except the bushing assembly thoroughly, including the section assembly (knocked apart so you can clean the feed) and the cap (especially the interior). If you have Rapido-Eze, soak the barrel in it for five minutes and then swab the interior with cotton swabs; this extra step can often remove ink stains that water won’t touch. Rinse thoroughly with water, and use a twizzle to dry the interior. Clean the exterior surfaces of the bushing and knob; if there is any thread sealant on the bushing, remove it.


Cut the sac to a length of " (24 mm) for a Type 1 barrel, or 1" (28.6 mm) for Type 2.

The sac length specified for a Type 1 barrel is correct for a short pen like the one illustrated in this article (about 4" long capped). For a full-length pen, the sac can be longer, but making it longer will reduce the ink capacity of the pen, and I see no reason to do so.

Drop the sac retainer into it, and insert the punch. Fit the end of the punch against the sac retainer, adjusting the sac retainer as needed so that it is flat against the end of the sac. Pinch the sac and stretch it back along the shaft of the punch to make the shape of the sac retainer’s square shape stand out as shown here:

Stretching the sac

Apply Vacumatic lubricant to the sac where it is pressed outward by the edge of the sac retainer. With your other hand, pick up the bushing assembly, and orient it so that the spindle cup aligns with the square shape of the sac retainer. With the punch, press the sac into the cup until it pops into place.

Popping the sac into the cup

Make sure that the nut screws easily and freely all the way onto the nipple. This is very important; if the nut is tight or catches as it screws on, you will not be able to secure the filler in the barrel. Your next step depends on whether you have a Type 1 or Type 2 barrel. For Type 1, continue with the next paragraph. For Type 2, skip to Assembling a Type 2 Barrel.

Assembling a Type 1 Barrel

Assemble the celluloid washers, the O-ring, and the nut onto the nipple in the same order they were in originally. If the one celluloid washer is distorted, be sure to replace it so that it points toward the nut, not the nipple. Do not screw these parts down tightly at this time! Insert the nipple into the open end of the sac. As the sac covers the edge of the nipple, push the edges of the sac inward all around so that they go between the nipple and the celluloid washer. Feed the nipple into the sac until the sac’s edge stops going into the gap between the nipple and the washer. Now screw the nut down just far enough to snug it against the O-ring. The assembly should look like this:

Assembled filler

Look through your supply of artists’ brushes for one that will fit through the pen barrel and has a handle that just fits into the hole through the hard rubber nipple. The handle must also be narrow enough that you can insert the blunted dental pick more than halfway into the barrel at the same time, from the same end. Wedge the brush’s handle gently into place in the nipple; you will use it to position the filler assembly in the barrel. See the picture below:

Brush wedged in bushing

Apply Vacumatic lubricant around the periphery of the O-ring. Feed the artists’ brush, bristles first, through the barrel from the back end toward the front. When the filler reaches the end of the barrel, it will not want to go. Use a cotton swab to push on the sac, forcing the O-ring into the barrel. Once the O-ring is past the threaded part of the barrel, it will move more easily. Use the brush to pull the filler gently into the barrel until the bushing reaches the end of the barrel. Rotate the bushing clockwise until it stops. (This is the same as rotating the knob counterclockwise, but with the filler parts in the barrel, that would not be easy.) Now begin rotating the barrel counterclockwise so that the bushing screws into it. As you do this, hold the brush and the bushing so that the only thing that moves is the barrel. (If you are doing it right, the filler parts inside the barrel will slip both around and downward in the barrel so that they stay in the same orientation with the bushing and also the same distance from it. This prevents the sac from becoming twisted.) Continue in this manner until the bushing is firmly screwed down.

Hold the barrel in front of a light source so that the light will shine through the barrel. Examine the sac to see that it is not twisted or compressed lengthwise.If it isn’t aligned as it should be, adjust it by rotating the brush to untwist the sac or by pulling slightly on the brush to extend the sac to its full length. Be careful as you do this; if you pull the nipple out of the sac, you will have to remove the filler parts from the barrel and start over.

Use the blunted fine dental pick to press against the nut, first on one side and then the other, while you gently pull the brush until it comes free from the nut. Remove the brush and the dental pick.

Releasing the brush

Carefully fit the wrench into the notches on the nut and then tighten the nut, working gently so that the freely-turning nut comes up against the celluloid washer and begins compressing the O-ring. Continue tightening as the O-ring resists the nut, causing the nut to turn less freely as friction increases. Compressing the O-ring lengthwise while its inside surface bears against the nipple will cause it to expand, wedging itself into the barrel and at the same time making a good seal. Stop well before the nut is so tight that turning it further requires significant force; forcing it further can dislodge the O-ring. Skip to Finishing Up.

Assembling a Type 2 Barrel

Insert the nipple into the open end of the sac. As the sac covers the edge of the nipple, push the edges of the sac inward all around to encourage the opening to return to its original size evenly all around the nipple. Feed the nipple into the sac until the sac’s edge extends about " (1.5 mm) past the widest point of the nipple, as shown here:

Assembled filler

Insert the nipple end of the filler assembly into the back end of the barrel as shown in this photo:

Assembling the filler into the barrel

Stop when the bushing reaches the end of the barrel. Holding the bushing, rotate the knob counterclockwise until it stops. Now, holding the knob and the bushing together, begin rotating the barrel counterclockwise so that the bushing screws into it. As you do this, the nipple will naturally find the hole in the center of the dividing wall. Continue in this manner until the bushing is firmly screwed down. The edge of the sac should be resting against the dividing wall.

Drop the nut into the front end of the barrel with the notches toward the open end. Use the blunted dental pick to guide it gently onto the end of the nipple. Carefully fit the wrench into the notches on the nut and then tighten the nut, working gently so that the freely-turning nut comes up against the end of the sac and compresses it firmly against the flat surface of the nipple. Stop well before the nut is so tight that turning it further requires significant force.

Finishing Up

Use the tongue test to see whether you have a good seal.

In case you are not familiar with the tongue test, here is how it works. Place just the front (threaded) end of the barrel between your lips and suck gently to create a partial vacuum inside your mouth and the pen. Place the tip of your tongue into the barrel opening and release the suction with your lips. The partial vacuum inside the pen should hold your tongue there. Let it rest for several seconds to ensure that you do not have a slow leak.

If the seal leaks, tighten the nut a little and test again. When you are satisfied that you have a good seal, reassemble the section, nib, and feed, and reinstall the assembly using non-hardening thread sealant.

As you are inserting the section into the barrel, be sure that the breather tube goes through the hole in the center of the nipple. If the breather tube stops against the nut and you push, thinking to make it go through, you can snap the breather tube or force Type 1 filler parts upward in the barrel, or both.

Immerse the nib and part of the section into water. Turn the knob clockwise and observe that bubbles come out of the pen into the water. Release the knob, wait two seconds for the sac to suck up all the water it can, and repeat the turn-and-release process until no more bubbles appear. To empty the pen, remove it from the water and repeat the turn-and-release process, turning slowly, until no more water drops out of the pen. Shake any remaining water out of the pen, fill it with ink, and enjoy the fruit of your labors!

  1. This O-ring is not a standard part. It is custom made, and as of this writing the only source I know for it is IndyPenDance.

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. My thanks to Dustin Windisch for the loan of the pocket pen illustrated in this article.

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