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Dec 09

Aurora 88 Piston Repair

Aurora 88 Piston Repair

I have long considered the vintage Aurora 88 to be one of the best pens to come out of Italy. Repairing the piston seal is generally pretty straightforward. The only real trick is that the hexagonal shaft has to line up correctly to be accepted into the receiver.

 

This pen, however, had  been in the hands of someone who attempted a more involved repair of the piston shaft itself. The 88′s piston shaft is threaded at the tip for the retaining/compression nut to screw onto, as shown in the photo below.

This particular piston shaft had been damaged: the threads were broken off. The previous restorer had the right idea but used items that would later cause problems, making future repairs difficult. Instead of a brass machine screw, that person used a small flathead wood screw. 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 had been used, the hole in the top of the piston needed to be drilled and tapped for a machine screw. We normally use a 0-80 round-headed brass machined screw for this repair, but the hole was already too large and had apparently been drilled by hand, as it was at an angle rather than straight. With the shaft chucked into the lathe, we could drill the hole out to the correct size to tap the threads for a 2-56 round-headed machine screw. To ensure that the threads were straight, the tap was chucked into the lathe’s tailstock, and the lathe was run at a very slow speed.

 

We normally use two O-rings of the same size for this repair. Unfortunately, the shaft was broken off so short that 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. We installed the retaining screw for alignment purposes, made a styrene washer, removed the screw, and then reinstalled the screw with the washer in place on top of the stack.

We applied a thin coat of silicone grease to the O-ring and then test-fitted the shaft and adjusted the seal parts to ensure a reliable seal. We then removed the shaft and coated the head of the brass screw with a good blob of two-part epoxy to protect it from corrosion.

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