I realize not everybody needs to put tab stops into an 82 year old typewriter, but if that happens to be a goal in your life, this Instructable is for you!
This LC Smith & Corona model 8 typewriter was built in 1930. I picked it up at a flea market and spent several weeks repairing and rebuilding it. One of the things that intrigued me about this old typewriter was that it came with "decimal tabulation" keys (see photo 3). These keys were designed to let the typist set tabs for a column of numbers, so they didn't have to use the space bar to align each number typed into the column. It was sort of a novel feature, but apparently never became very popular, because they discontinued this feature after only a few years.
During the process of restoring this old typewriter, I found that the tab stops that worked with these keys were missing.
Well, no problem, or so I thought.
I checked ebay -- nothing. I checked google -- nothing. I checked a couple of vintage typewriter forums, and found that everyone who has attempted to rebuild one of these pretty much ran into the same problem. The tab stops seemed to always be missing, and no one had a source for them.
So, I decided to make my own.
Step 1: How tab stops work
I knew I would need to make two tab stops (one for the decimal position, and one for all the others). I decided I would go ahead and make 5 instead of 2, since I could use the stops to set multiple tabs if I wished. I couldn't find a photo of what the tab stops looked like, but it wasn't too difficult to figure out where they should be installed and what they needed to look like to be functional.
The square bar in photo 2 was made with teeth on it, and the tab stops were made to slip over the teeth. In photo 3 I have pressed one of the tabulation keys, and if you look closely you will see a small metal tooth has projected outward, and this tooth is designed to meet a tab stop and force the carriage to stop.
I found the groves between the teeth on the square bar to be 3/64ths of an inch wide. Luckily, I just happened to have some precision ground tool steel that was 3/64ths of an inch thick!