3 Bank Pivots & Bushings
After sourcing parts from across the pond and machining some parts from scratch, this Underwood 3 Bank is back up and running again. Broken Links
This machine arrived at my doorstep, having a known issue with one of the keys. Originally I'd been expecting that this was a disconnected linkage, but ultimately turned out to be a bit more trouble than originally planned. Instead of a loose wire, a whole arm on one of the pivots has snapped off and was missing entirely.
Looking closely into the basket you can just barely make out the broken arm on the pivot. I briefly entertained the idea of welding or machining a new pivot arm, but you can see this whole assembly is actually riveted in place. If this linkage were to maintain low friction and in that small space, I was likely going to need to drill out the old rivet and replace it somehow - not something I was necessarily eager to try yet.
Once out of the machine you can really see how it just snapped clean off. Hard to imagine what would have done that. In practice, this would mean that the D keytop simply was a dead key. From these images you can see how the bottom of the bracket is threaded; they mount to a crossmember with a pair of screws from underneath, requiring the machine to come off the bottom of the case.
After going back with a fellow in Finland, managed to find the proper matched pivot from a parts machine. These are pretty cozy machines without a ton of space to work with, but it worked out. As with many of these repairs, replacement with original parts can often be best!
Replacing Bushings
As received, one of the bushings was missing. Without this part, the carriage release could wobble to the side, slipping off the release arm and ultimately causing it to require some creative handling to release the carriage.
The field expedient solution was just to toss a couple washers in there, which worked well enough but certainly felt like it wasn't true to the elegance of the machine. Spending a little time on the lathe though, managed to quickly cut down a replacement. The original dimensions were copied from the other one of these in the collection, however they would have been easy enough to approximate as the only critical dimensions are a min-max width of the part, with a pretty wide tolerance.
The original part was made in a mild, blued steel, but since this part doesn't see any real pressure and it's far easier to machine, I opted to make this from a scrap of aluminum I had laying around. Center drilled, turned down to roughly the correct OD, and chamfered the top to make sliding the platen on a little easier.
Below you can see it in place, the aluminum blends right in with the stainless parts, even if the original was blued steel. While OEM replacement can be great in lots of places, for parts with simple geometry, the machine shop can square this circle.
Using the 5T in Nu-Mode to jot down the dimensions before taking it to the lathe. Finally, a use for all these typewriters!
