Restoration Supplies



My parts originally came from Custom Pen Parts in the UK:
[Onoto 7.78mm Repair Pack]

This kit came with both the cork seal and new piston gasket necessary for restoration. It also came with a small backing washer to go behind the piston gasket. This part isn't necessary in all models. My earlier model has a groove in the plunger head instead of a separate gasket. It is up to the restorer to determine if a backing washer is needed. The parts were all coated in some kind of oil, likely relating to how, quote, "the corks have been impregnated with medical grade paraffin wax". This oil was removed from the gasket before installation. Some excess of the oil was removed from the outside of the cork seals to avoid getting it on the threads for the threaded washer that closes the back of the pen. The last semi-optional part the kit came with is new pin material. If you lost or damaged the pins that hold the piston knob or shaft nut in place, the small piece of material included in this kit could replace them. This part of the kit went unused and the original pins were reinstalled in this guide.

Other tools you need include:
  • Pick of some kind to remove the old cork seal
  • Rod for pushing the new cork seal into the back of the pen
  • Thin pin driver for driving out the pins that hold parts of the piston together
  • Grease for the seals during final assembly (I will be using Dow Corning Molykote 111)
  • Tool for removing the threaded washer - check assembly/disassembly step 4 for what properties the tool needs

Tour of the Parts




First, a tour of the parts of the Onoto. The parts that will almost certainly need replacing are the cork seal in the back of the pen and the conical gasket on the head of the vacuum piston. My pen already had the old piston gasket removed at some point in the past, but yours may have small pieces of hardened rubber from the degraded piston head inside the body. Simply clean these out and dispose of them.

Assembly / Disassembly Instructions


Assembly Step 1: install new gasket

The new piston gasket can be installed. This conical gasket is a recreation of the original part. I think I may have seen some reports of people using flat gaskets (similar to those on later Sheaffer vac-fills) for repairing their Onotos, but I cannot guarantee if they would actually work. If your pen needs a separate backing washer, it is installed during this step (instead of how the pen above has a grove in the piston head the gasket can sit in, the surface will be flat and the backing washer will sit around the raised base of the gasket).

Disassembly Step 7: remove any gasket remains

By this point the piston head should be dismantled and any final debris from the degraded gasket can be removed. If parts of the gasket are strongly stuck to the piston head a tool such as a dental pick can be used to gently remove them.

Assembly Step 2: reassembly of piston head

The shaft nut of the piston head can be screwed back onto the piston shaft with LEFT HAND THREADS. Once the hole through the shaft nut and the piston shaft are aligned, the pin can be reinserted until flush on both sides and assembly of the piston head is complete.

Disassembly Step 6: disassembly of the piston head

Search the shaft nut for a small hard rubber retaining pin. This pin may be difficult to spot due to a flush finish with the shaft nut. Once found, use a small blunt metal rod to drive the pin out from the piston shaft and shaft nut. The pin is quite small, so a thin pin driver is needed. I personally used a large sewing needle that I broke the tip off of and sanded flat. Be careful driving the pin out to not put unnecessary stress on the piston shaft, you may risk breaking it. After the pin is removed, the shaft nut may be unscrewed with LEFT HAND THREADS.

Assembly Step 3: replacement of cork seal

A new cork seal can be inserted into the back of the pen. If you're using o-rings instead, this is the step to install them. If your seals are coated with an oil or wax suspenion like mine, make sure to not let it get onto the threads for holding the threaded washer. If it does, clean the threads. Any kind of lubricant on the threads may make the threaded washer back out over time.

Disassembly Step 5: removal of old cork seal

With a small tool, such as a dental pick, the old cork seal can be pulled out from the back of the pen. Don't worry about destroying the cork in the process, as it's going to be thrown away anyways.

Assembly Step 4: closing the back of the pen

If your kit needs a spacer (such as when Richard Binder used o-rings in his guide), place it behind the seal before closing up the back. Now take the threaded washer and screw it into the back of the pen. First do so just by hand and using gentle friction. Once near the end of threading the washer, the tool used during disassembly can now be used for final tightening. Be careful not to cause too much damage to the threaded washer during this stage.

Disassembly Step 4: opening up the back of the pen

The back of the pen, which holds the cork, is closed with a small threaded washer. On some editions of the Onoto this washer is designed to be removed with a special split driver tool. However, this verion does not have such a feature and the exterior surface of the washer is smooth. To remove the washer, find a small tapered tool with sharp edges; for example a triangular file (this is the tool Richard Binder used in his restoration). I personally used a small metal tool with a flat sharp end designed for sculpting clay. Push the tool into the center of the washer just enough to have it get a grip. Then unscrew the washer. The goal is to have enough grip without causing unnecessary damage to the washer during removal.

Assembly Step 5: installation of the piston

At this point, the piston can be inserted into the front of the pen body and through the cork seal. This would be the time to grease the piston gasket and probably apply a little grease to the piston shaft itself. Avoid grease on any threads that are not pinned in place.

Disassembly Step 3: removal of the piston

With the piston detatched from the knob, the shaft can be pushed out the front of the pen.

Assembly Step 6: attaching the piston knob to the shaft

Screw the piston knob onto the shaft with LEFT HAND THREADS. Once the hole through the shaft and piston knob are aligned, the pin can be reinserted until flush on both sides.

Disassembly Step 2: removing the piston knob from the shaft

Search the piston knob for the small retaining pin. This pin may be difficult to spot due to a flush finish with the piston knob. Once found, use a small blunt metal rod to drive the pin out from the piston shaft and piston knob. The pin is quite small, so a thin pin driver is needed. I personally used a large sewing needle that I broke the tip off of and sanded flat. After the pin is removed, the piston knob may be unscrewed from the shaft with LEFT HAND THREADS.

Assembly Step 7: reattaching the section

Simply thread the section back onto the body, fully closing the pen.

Disassembly Step 1: temporarily removing the section

Unscrew the section of the pen. Access to the internals is necessary and the section can be placed to the side until restoration is complete.

The De La Rule Onoto is now fully assembled and ready for use!