How to Repair the Piston in a Tibaldi Mº 60

(This page revised October 27, 2013)

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Introduction

Among modern pens, the Tibaldi Modello 60 has deservedly achieved a strong following. It’s an excellent pen, attractive and well made, and good in the hand.

Fountain pen

But it suffers from a fatal flaw, in the form of a design error. The piston’s seal is an O-ring held in place between two flanges molded into the one-piece piston. To allow for more lateral play and smoother operation, the pen’s designers chose to make the shaft on which the O-ring rides slightly smaller in diameter than the ring’s inside diameter. Normally, this design would allow ink to leak between the O-ring and the shaft; but the designers also placed the two flanges slightly closer together than the thickness of the O-ring, clamping the O-ring between the flanges and making a good seal. The flaw is that the flange at the end of the piston is not sturdy enough, and it breaks under the stress of squeezing the O-ring. Its failure destroys the sealing integrity, and the pen will no longer draw ink. This article explains one way to repair the piston.

Note
Note
If you do not have access to the right tools and the skill and experience to use them properly, I recommend that you not attempt this procedure using makeshift techniques. The risk of damaging or destroying the pen is far greater if you use “ordinary” tools.

Tools Required

Parts Required

Supplies Required

Disassembly

To disassemble the pen, unscrew the nib unit. Unlike most similar pens, the Mº 60 has a standard plastic nib sleeve cemented into a threaded metal ring with two notches on the exposed surface for a pin spanner.

The nib unit screws into a transparent plastic reservoir in which the piston runs. With the nib unit free, you can now push the entire mechanism/reservoir assembly backward out of the barrel.

Inside the front end of the reservoir is a metal collar that serves to compress an O-ring against a removable plastic disk to seal the reservoir. Remove these three parts by carefully fiddling them out with a dental probe. (Be careful not to damage the sealing surfaces!)

In most cases, the failure of the piston results in a flood of ink into the back end of the pen. By continuing with the disassembly, you can clean all this ink out. The actuating mechanism is secured to the back end of the reservoir by a threaded collar that screws onto the threaded end of the reservoir. Operate the piston knob to drive the piston as far down toward the front end of the reservoir as possible, then unscrew te collar and remove the mechanism. Now, if the piston hasn’t fallen out, you can use a long probe to push it al the way out of the reservoir. Use the cotton swabs and water to clean out the interior of the barrel as well as both the exterior and the interior of the reservoir and the piston mechanism. Here is the pen in pieces after cleaning. The piston knob can be pulled off the knurled shaft of the mechanism, but there is no need to do this, and I recommend leaving it as it is.:

The Tibaldi Mº 60, disassembled

The piston’s failure seems always to consist in breaking across the center, with half folding away from the O-ring. Here is a close-up of a broken piston:

Piston with plastic plate and screw

Repair

Absent a replacement piston, the only possible repair is to create and install a replacement for the broken flange. (And given the cause of the original failure, simply replacing the failed part doesn’t seem all that attractive anyway.) So the necessary procedure is to remove the remains of the broken flange, cut a piece of plastic sheet for a new flange, and find an appropriate method of fastening the new flange to the piston. The fastener I chose for the first Mº 60 I did was a brass 2-56 flat-head screw as illustrated in this article; but I have since switched to extra-tough Nylon to eliminate the risk of corrosion. Here’s the cleaned-up shank with a square of white polystyrene sheet and the screw:

Piston with plastic plate and screw

Make a protective sleeve for the piston by facing one end of the 9/32" plastic tubing in the lathe. Sand the end smooth.

Chuck the piston in the lathe, protecting it by inserting it into the sleeve you just made. Cut away the remains of the broken flange. Drill a Nº 50 hole in the end of the shaft, going at least 1/2" deep. The hole must be deep enough that the screw can seat all the way down to its head. Shown here is the drilling operation:

Drilling the piston

Tap the hole using the 2-56 tap in the pin vise, making sure the screw will indeed screw all the way in. (This operation can be done in the lathe, but there is a significant risk of splitting the shaft by going past the bottom end of the drilled hole.)

Tapping the piston

Cut a 1/2" square from the polystyrene sheet. The quickest and easiest tool for this purpose is the sharp scissors I list in the Tools Required section. Drill a hole through the center with the Nº 43 drill. (It’s not necessary to locate the exact center.) With your X-acto knife, bevel the edge of the hole on only one side to create a countersink for the flat-head screw. Cut just far enough to reach the other side; do not go so deep that you enlarge the hole. Test-assemble the square to the shaft. There should be a little of the screw head protruding above the surface of the plastic sheet. Remove the screw, apply shellac to its threads, and secure the plastic square firmly to the piston shaft with the screw:

The piston with the plastic plate in place.

Cut away most of the extra plastic with scissors, then chuck the assembled piston into the lathe again to finish turning the new flange to its final size (the same diameter as the remaining original flange.

The piston assembled

Cover the face of the piston with epoxy to secure the screw and, if the screw is brass, to prevent corrosion. The epoxy also creates a smooth surface, preventing ink buildup under the edge of the screw head. Set the repaired piston aside overnight to allow the epoxy to set completely.

The finished piston

Reassembly

In most cases, the original piston O-ring will be perfectly usable. If it is damaged, replace it with an M2.0×4 O-ring (preferably Viton for long wear).

Grease the O-ring lightly, assemble it onto the piston, and clean excess grease from the exposed face of the piston. (See the photo above.) Reinsert the piston into the reservoir, using a probe or a length of the 9/32" tubing to push it all the way to the back. Reattach the piston mechanism to the back of the reservoir, being sure to screw the threaded collar down firmly but not with so much force that you crack the reservoir.

Reinstall the piston/reservoir assembly in the pen body from the back, being careful to align the notches on the reservoir’s front end with those on the inside of the section as you slide things together.

Insert the plastic disk into the section, using a probe to make sure it lies flat against the shoulder of the reservoir. Insert the O-ring and the metal collar. Use a toothpick or a wooden match to seat the collar against the O-ring, then screw the nib assembly in firmly.

Check the nib alignment, readjust it if ncessary, and enjoy the pen!

Notes:
  1. The word “Modello” is not part of the pen’s name. It’s Italian for “pattern” or “model”; the pen is actually a Tibaldi with a model number of 60 (like the Parker 61 and 75).


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