Aurora 88 Piston Repair
I have often considered a vintage Aurora 88 to be one of the best pens to come out of Italy. It is generally a pretty straight forward repair when it comes to the piston. The only real trick is the hexagonal shaft has to line up correctly to be accepted into the receiver. This one however had previously been in the hands of someone attempting a more involved repair of the piston shaft. Your typical Aurora 88 piston shaft is threaded at the tip for the retaining/compression nut to thread onto as seen in the photo below.
This particular piston shaft had been damaged and the threads were broken off the top of the piston shaft. The previous restorer had the right idea but used items that would later cause problems making future repairs to the shaft difficult. Instead of using a brass machine screw for the repair, a small flathead wood screw was used. Under the wood screw was what appears to be a thin brass washer. Over time the screw began to rust.
You can see from the photo above the components used on the previous repair and the state they were in, even after being cleaned. Because a wood screw was used, the hole in the top of the piston needed to be cleared and preped for a machine screw. Normally on this type of repair we like to use a 0-80 round head brass machined screw, but the hole was already too large. Also the hole was most likely done by hand as it was at an angle rather than straight. The shaft was chucked into the lathe so that the hole could be bored out to the correct size to tap the threads for a 2-56 machine screw.
Normally we like to use two O-rings of the same size for this repair. Unfortunately the shart was broken so short this was not an option. We used a smaller O-ring first to give us the height needed so that the larger O-ring would compress properly when the machine screw was tightened. The retaining screw was put in place for alignment purposes and then a styrene washer was cut and placed on top. The 2-56 round head brass machine screw was then screwed into place.
A thin coat of silicone grease was applied to the O-ring and the shaft was test fit and adjusted to make sure it had a good seal. We then removed the shaft and coated the head of the brash screw with epoxy to keep it away from ink and any risk of corroding.