But a lot of this is going to come down to how narrowly you define things, as the ‘Model T’ versus ‘automobile’ example. Or, as another example, long-distance communication across electrical wires is very much alive and well, but I seriously doubt any working installations still use telegraph technology (but then again, there are certainly museums with working telegraphs somewhere. If flint knapping is an existing technology, then is anything in a museum that could be repaired an existing technology?)
Anyway, not a ‘tool’ specfically, but my nomination for lost technology is Greek Fire.
Mechanical powder testers. Gunpowder, both smokeless and black, still varies from batch to batch. Mechanical testers have been replaced with more precise electronic equipment.
Edited to add: I’m wrong. Replica flintlock powder testers are still made and sold through such outlets as Dixie Gun Works. Whether anybody actually uses one to test powder is questionable.
Surveying and the legal title to land is pretty tradition-bound in some ways. I remember back in college, 15 some-odd years ago, that the land plats and titles that I’d occasionally register at the courthouse referenced the original Stephen F. Austin land grants for the land in question. At the time, that was about 160 years prior and 3 nations before (Mexico, Texas, US)
I’ll take a guess and say that mechanical adding machines are no longer made. There just isn’t much use for them with the advent of electronic calculators.
I think we ought to also draw a distinction between “in commercial manufacture” and “the occasional one-off built by highly skilled craftsmen” also. There are probably lots of the former, but just about anything could be made by the latter, and IMHO, it doesn’t count as “still being made.”
I’m 27, and I remember using 5 1/4" floppies in kindergarten and elementary school. They were on their way out even in elementary school, though, and I don’t believe I ever saw them in middle or high school. In any event, I would expect a lot of people my age to be familiar with floppies of this size. Current undergrads, though (23 or younger) might not. And I’d be surprised if current high school kids were familiar with them.
A popular urban myth has the blueprints for the Saturn V either lost or purposely destroyed. The blueprints and other plans still exist on microfilm at the Marshall Space Flight Center.
Even less likely: Professional quality tape cartridge players and the tapes that ran in them. These where what 8-tracks were developed from, but no radio station uses them any more. Everything is digital.
8-inch floppy drives and floppies. I have one in my office, but they were obsolete 25 years ago.
Presto Automatic Hot Dogger. Quite the appliance in dorms in the 70s. You put the hot dog between two electrodes and the current cooked them. A guy in the dorm made his own with a couple of nails, some wood, and an electrical cord from the outlet to the nails. Commercial models had interlocks to keep them from electrocuting you. Probably.
My god, my jaw just locked itself shut after seeing that extraction key.
How about old quack medicine products? Things like the Radium Emminator: Museum of Radiation and Radioactivity
Which is a device intended to infuse your water with uranium.
Really. People thought it was healthy. There are a whole bunch of products like that from the same time period.
I suppose you could say that modern day radiation therapy for cancer is similar, but that’s a real reach.