I bought a few bits a couple of years ago from a guy that ran a
to another company and retired. He said they contacted him shortly after to come and help them set up the machines for a job which he did but ultimately they were on their own after that. It seems he had worked with them most of his life and knew them well but fewer and fewer people are about who know how to use them so they had become largely useless and went for scrap.
CNC lathes. CNC-savvy machinists know how to set these up, and they can change over from one job to another in minutes if no tools need to be changed, and in an hour if they do. The cam-type screw machines need very tricky setup with a lot of trial and error until the parts come out within tolerance.
The screw machines can generally beat even a very good CNC turning center making just one part, day in and day out. The tool to tool time on a screw machine can be less than a second. But, few people today know how to set them up and maintain them.
But that wouldn't be so unless they weren't being used prior to losing the knowledge base--there'd still be plenty of people who did know them if they hadn't been unused for quite some time already.
I "know nuthink!" per Schultzie's line about commercial screw production but one presumes more highly automated machines did replace them and probably including at least some robotics but what, specifically?
Or, is it simply that there's no US production left; it's all in China and the like...
Well, it weighs more than 16 tons, which makes it a bit difficult for a small shop to justify, and presumably makes the scrap value high enough to make it expensive (counting scrap value and rigging, much less what it wants for power, or a non-scrap price.)
Everyone else has covered this well, but you bring up something here that's worth adding: Extended high-volume continuous production has always been a rare exception in manufacturing. Back in the 1960s, and even in the '50s, there were articles (and, I think books) on the subject "the myth of mass production." Most production in the US and elsewhere has been batch production, and the time and cost of changeover has always been a big factor in production costs. Screw machines are slow to change over and require some expertise; CNC lathes are much faster. And they are much, much more versatile.
"Back in the day", when there were carburetors, they had 100 special parts on each one, needle valves, jets and the screws that held it all together, that were made by the barrel on screw machines. Lots of other products has screw machine-produced parts, too. All the threaded plumbing fittings were made on screw machines. Well, a lot of that production has moved overseas, some of those products are made differently (think fuel injection) and a lot of these parts are molded or cast in some manner now. So, there is less demand for this. Also, there are rotary transfer machines that are used to make all sorts of reall high production parts. These can even beat a screw machine for throughput.
For one thing, screw machines were at one time used to make -- SCREWS! I suspect that it would be VERY rare to make screws that way, now. Mostly, they'd be coined and have the threads rolled. Nowhere as precise, but precise enough to hold some gadget together.
"Re-shoring" has been going on for about 10 years or so. As the Chinese, Vietnamese and Indian economies continue to build up, the incredible difference in labor cost gets smaller. And then, the cost and delay of shipping and all the communication issues start to become a problem. I'm pretty sure this trend will continue.
Yeah, mostly little Swiss automatics, though, not the big ones. Lots of fuel-system parts are still made on those machines (Citizen-Cimcom, Tsugami, etc.) They're basically the same machines, only now they're CNC instead of cam-controlled.
Hmm...for the past 60 years or so, actually on dial-index transfer machines.
...sort of. Cold-headed, actually.
Some specialty screws and bolts are still turned, but the big volumes are made on ancient, beat-up headers and roll-threaders in countries where they work in their bare feet.
When I was at Wasino, we turned the big-end con-rod bolts for Cosworth racing engines on our precision CNC lathes, which would turn to +/- 50 microinches. I think they were $24/each, or possibly $24/pair, when we were done. d8-)
Do you remember Dobbie Dave, who used to hang out here? I wrote an article about him and his shop about 15 years ago. Most of his income was (and maybe still is) from production on his four 1947 B&S, leather-belt-driven screw machines (known commonly as "Brownies.")
He found himself a niche. He was a sole source, making parts for lie-detector machines, and a couple of other little hinge pins and such.
I caught up with an old boss of mine over the weekend and the company he works for has a manufacturing branch in China which has it's issues but is generally a benefit to the company. He mentioned that now there are regular trains, very long ones, that run from China to Europe and they get things shipped on those as they're far quicker than getting things shipped by sea from China to Europe, the UK.
I build model engines and repair old things and like to used NOS screws and nuts. Last year at a local FM i bought a flat [soft drink or beer case bottom] of small [6 to 2] screws from the late 40;s or 30's for$10. They are so nice compared to the crap you get nowdays that are formed , rolled cold headed. I was lucky. You should see the sharp edges on phillister heads. CP
My understanding is that the Thor Power Tool decision in 1979  screwed up (pun intended) the bolt and rivet industry much as it did the publishing industry.
Company gets an order for, say, 100,000 3/16" x 1-1/8" button-head soft iron black-finish rivets. So they tool up, make 500,000, deliver the 100K order and stock the remainder. Same for maybe 2,000 varieties of rivets in dozens of styles, size and materials. After a few years, they can deliver almost anything from stock. Similar for bolts.
Until keeping that stock on the shelf becomes a tax liability. Then they go to making just the order and the customer has to pick up the set-up and material procurement costs rather than having the maker spread them over several/many years.
Under that rubric, CNC may be a cheaper way to go than screw machines.
I vaguely recall that there was an "Acme Bolt & Rivet" case as well but I can't find a reference.
I learned to distinguish between rolled and cut wood screws when I was a kid. It's been decades since I saw a cut wood screw other than old stock in my own dusty parts bins.
As an aside, 50 years ago I bought some 1/4" x #0 wood screws from a hardware store going out of business after 3 generations. Just had my second occasions to use some of them, to screw a carefully fitted copper patch to my (tobacco) pipe to stop two cracks from joining and wrecking the pipe. Second time I've done that and the other pipe is still good after 20 years. But I do wonder just how 1/4" x 0 screws were made.
Hmm. I never saw that reference to publishing before. It's interesting.
I don't know how much the tax issue drove the big switch to minimal inventories. Maybe it was a big issue, but the one that was touted over and over, as US industry tried out just-in-time (JIT) inventory control, was the shear interest and rental charges for maintaining inventories. JIT looked like an answer, and it has been for many industries.
But my sister-in-law, who was a buyer of castings and forgings for Caterpillar, said they eventually renamed it "OSWO," for "Oh shit, we're out."