I use my TWSBI Vac 700 for my ink sampling and with all the different inks, and multiple nib changes for each ink, the pen gets filled and emptied a lot. The Vac mechanism has easily gone through over 100 cycles even without considering pen cleaning. The filling rod was getting very stiff and sticking. I was afraid I’d break the pen or slip and send an ink bottle across the table or crush a nib.
I had put the pen aside until I had proper time to tackle the issue. In retrospect it wasn’t such a big issue. But it was the first time and I was hesitant.
First issue, what happens if I get the silicone grease in the pen? In a round about way it came to me that nothing would happen. A recent Goulet Q&A included a question about why metal pens couldn’t be converted to an eye drop filler yet the Vac 700 had a metal filler rod. I’d never though about it myself and basically the answer was what I expected. The metal used is picked to not react with the ink. What’s this got to do with silicone grease? Well, a bell went off and I realized silicone grease is used exactly because it’s inert when mixed with ink. While I wouldn’t want to shove it into the feed, or pour it over the metal rod there wouldn’t be a problem with just enough to loosen things up.
I used the included silicone grease and applied a little to the rod and worked the mechanism without taking the pen apart and that helped greatly, but it still stuck a little. So I opened the pen with the included wrench and applied a little silicone grease below the rear cap and worked the mechanism a few more times. The included silicone grease (from TWSBI, received with the pen) was in a dropper bottle so it was easy to just apply a little.
The only catch is to extend the plunger about half way and insert the seal into the pen before screwing on the rear cap. I screwed on the cap with the seal right against it and the seal was wedged into the top of the pen. No sense having to force it.