I notice that most of the replacement Underwood 5/6 feet that I see online are basically a tapered rubber cylinder on a bolt. My Underwood 6 came with two feet that are made up of a rubber foot, a felt sleeve, and a metal bell (see photo).



Was this the original way Underwood standard feet were made? Or, was it only on some machines?

I thought it a pretty interesting technique for dampening vibration from the machine, and if authentic, reproduce this for all 4 feet. I was thinking of 3D printing the rubber. Not sure yet how to make the felt sleeve. Any leads anyone knows of? 

Hello from Seattle!My typewriting journey began in typing class in the mid 1980s in a classroom filled with, I think, Olympias (I don't remember the model). I took the class so that I could more quickly program the shiny new Apple IIe my school had just acquired, but I also enjoyed writing on my mom's typewriter at home.
  Fast forward to 2008: while scanning ebay for 19th century pocket watches, I purchased an L.C. Smith model 8/10, followed shortly thereafter by a Corona 3 portable. I loved writing on them and seeing the ingenuity of the machinery. Later, in 2014, while strolling through a local flea market, I happened on someone selling scores of typewriters at fairly low prices. He told me that anything that didn't sell that day would be sold to the chopper a few stalls down to harvest keys. I saved what budget and space could afford: An Oliver 9, Remington 6 and 12 standards, a Royal KMM, and a Royal Quiet Deluxe. 
Recently, my typewriter fever was rekindled by a combination of watching California Typewriter shortly after some folks at work asked me to try to determine the typewriter that had written an old letter from a departed uncle. (Pretty sure it was an U.S. Navy Underwood Universal portable mill). Thus more typewriters, tools, etc.
I really enjoy writing on typewriters - it's a completely different process than writing by hand or on computers. I also equally love working on typewriters, breathing life into neglected, broken machines. Plus, it fits nicely alongside my day job (typographer at a software company), and other passions like fountain pens, vintage BMWs, and late 19th / early 20th century design. (and my 3D printing hobby may come in handy, too).
Looking forward to learning from all of you!