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How to Repair a Cracked Safety-Pen Operating Shaft

(This page published February 9, 2023)

Reference Info Index | Glossopedia  ]



Retractable safety pens come in two major varieties. First, there is Moore’s Non-Leakable Safety Pen, which uses a simple, straightforward push/pull system to extend and retract the nib. The second kind, the one we are interested in here, is the kind that has a knob at the back of the barrel to extend the nib when the knob is turned. Even though many other companies made them and Waterman didn’t even invent them, these are commonly called Waterman-type safeties. They all use a long-pitch helical cam to drive the nib shaft out or pull it in, and herein lies a problem. The cam system consists of a tubular shaft with slots cut in its wall and one or two grooves cut along the inside of the barrel. Inside the tubular shaft rides the smaller shaft that is the nib carrier. The weakest link is that tubular shaft. It’s fragile, and it can be broken if too much force is applied in an attempt to convince a nib that won't stay extended that it should do so. When the shaft breaks, it usually breaks by splitting at the forward end (closest to the nib), which is not supported by a central shaft. This article describes how to repair this damage.

Tools Required

Supplies Required

As you follow the instructions in this page, refer to this diagram to identify the various parts.

Fountain pen schematic

In the diagram above, the slots in the operating shaft are long helical cuts. The purple crosswise pin is riding in straight slots that run along the inside of the barrel. As the green operating knob turns the shaft, the slots in the shaft force the pin to move along the barrel slots, extending or retracting the nib. You can see the potential here for breakage if too much force is applied in an attempt to move a nib that’s not extending or retracting properly.

Waterman started producing safeties in 1907 or 1908. The earliest version of Waterman’s safety had its mechanism “backwards,” with the helical slots running along the barrel wall while the straight slots were cut into the tubular shaft. These earlier pens are relatively uncommon, and you can identify them by seeing whether the nib spins around as it moves in and out. If it does, the pen is an early one. The early pen shown at the top of this page is a Nº 15VS. This article illustrates the repair using that pen, but the procedure is the same in either case.

Waterman’s pens used two slots in the shaft and two in the barrel wall, with the pin passing through the shaft and the nib holder shaft with its ends in the slots in the barrel wall. Some manufacturers' pens had only one slot in the shaft and the barrel wall. In these pens, the back end of the nib carrier shaft is usually bent over and filed to shape so that it fits the slots.

Hard rubber is something of an ornery substance. Exposed surfaces oxidize; this can be seen as a brownish discoloration, but oxidation occurs long before there is any evidence of discoloration, and anything other than a fresh break or a freshly machined surface should be considered to have oxidized. Oxidized hard rubber cannot be glued reliably; it might stick together, but the glued joint will have no mechanical strength. Freshly exposed surfaces, however, can be glued with epoxy glues, and the repair described her relies on this fact.

In the pen discussed here, the slots had both split at the end closest to the nib as shown below. The break itself is just barely visible in the photo as cracks; no fragments were lost. When the shaft is split in this manner, the pen will work, sort of, but the shaft is always at risk for further breakage. However, replacement parts are extremely thin on the ground, especially for the earlier Waterman pens or those of other makers. The repair consists of making a collar to fit around the damaged shaft like a cap band. It’s a quick repair, and if done correctly it will last as long as the pen. (The broken surfaces have oxidized in the years since the part was broken, and simply gluing them back together won’t work.)

The damaged shaft
I recommend using styrene (Evergreen brand, made in telescoping sizes) or butyrate tubing (Plastruct brand) to make the collar because these plastics are less likely to break during fabrication than hard rubber. For our purposes, the advantage butyrate tubing offers is that its wall is thicker than styrene’s wall, thus offering the ability to fit a greater range of pen sizes.


Uncap the pen and set the cap aside. The barrel cap is screwed into the main portion of the barrel, and you must unscrew it. Do this delicately to avoid breakage. Although this joint was originally made precisely enough that no adhesive or sealant was required, some repairers might have sealed it with shellac as an extra precaution against leakage, and heat might be required.

The threading of the joint between the barrel and the barrel cap is usually — but not always — an ordinary right-hand thread. In some cases, however, e.g., German Regina-branded pens, it is a left-hand thread. In either case, the male-threaded barrel cap is screwed into the barrel. Attempting to unscrew this joint in the wrong direction can shatter the barrel or break off the threaded portion of the barrel cap.

With the barrel cap unscrewed, slide the mechanism out through the back of the barrel. Disengage the crosswise pin to separate the nib carrier shaft from the operating shaft. Remove the knob from the shaft, being careful not to lose the pin that secures the shaft into the knob. Slide the shaft out of the barrel cap. Clean the various parts, and set aside the nib carrier assembly, the knob and its pin, the barrel cap, and the crosswise pin (if any).


Measure the outside diameter of the tubular shaft at the open end. Call this diameter X. Measure the wall thickness of the tubular shaft. Call this number Y. Subtract Y from X. The remainder is the desired inside diameter of the collar you will make. Call this number Z. Write down X and Z; you will need them later.


Choose the smallest styrene tubing whose outside diameter is larger than X. Measure this tubing’s inside diameter. If it’s smaller than Z, you are golden. If it is not smaller than Z, you have to make a choice:

Prepare one end of the tube by chucking the tube in the lathe and facing the exposed end. (If you fused a smaller tube inside one end, that’s the end you want to use.) Cut off about 2" (~50 mm) of the prepared end.

Find the largest drill that is smaller than or equal to diameter Z. Chuck the drill into the tailstock, and drill out the inside of the tubing. Run the lathe at about 350 RPM, and cut slowly enough that the drill does not catch but no slower than necessary. The finished surface should not be spalled by heat but does not need to be polished smooth; epoxy glue will hold better if the surface is slightly rough. Measure the resulting inside diameter. Call this number Q.

Insert the drill backwards into the tailstock chuck as far as it will go, clamp it down, and run the tailstock in so that the smooth end of the drill slides inside the tube to serve as a mandrel to keep it from flexing. Turn down the tubing to diameter X. Then use a sharp cutoff tool to cut off a collar " (3.2 mm) wide, as shown here. Deburr the collar.

Turning the collar

Cut about 2" (~50 mm) of the largest styrene tubing whose inside diameter is smaller than X. Using the X-acto knife or a razor saw, split the tubing and deburr the inside. Spread this tubing and slip the operating shaft inside it, leaving about " (4.6 mm) of the tubular end of the shaft exposed. The slit in the tubing must be spread far enough that you can see the shaft when looking through the slit. If you cannot see the shaft, remove the shaft and shave down one side of your slit until you can see the shaft when the two are assembled. Being careful not to align the slit so that it is under a chuck jaw, insert the assembly into the lathe chuck with about " (6.4 mm) of the styrene tubing exposed. Tighten the chuck just until you cannot turn the operating shaft within the styrene tubing. Do not overtighten.

Find the largest drill that will slip inside the tubular shaft. Insert this drill backwards into the tailstock chuck to serve as a mandrel as you did for the collar tubing.

Turn the exposed end of the tubular shaft down to diameter Q for a distance of 1/8" (3.2 mm), as shown below. Use a very sharp cutting tool, run the lathe at about 600 RPM, and cut in extremely small increments in order to avoid snapping off part of the shaft. Test-fit your collar onto the end of the shaft. It should slip on but not be a sloppy fit. If it is too tight, turn the shaft down another 0.002" (0.05 mm) and test again. As with the collar’s interior, the finished surface does not need to be polished smooth.

Turning the shaft

Epoxy the collar onto the shaft. After the epoxy has set, clean off any epoxy remaining on the outside or inside of the shaft assembly. It might also be necessary to use the X-acto knife to cut out a tiny bit of the collar as shown in the image below, where it has impinged into the shaft slots. Do not cut the shaft itself as you do this; removing material from the slots might alter the action of the assembly enough to keep the nib from staying securely in position when extended. This is what your shaft should look like:

The repaired shaft


Reassemble the mechanism:

The reassembled mechanism

Reinstall the mechanism in the barrel, test its action, and then screw the barrel cap down firmly by hand. Using the rubber gripper square and the section pliers, tighten the joint just a squeak further, to seal it. Enjoy your repaired pen!

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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