Manufacturing Screws and Nuts

to make them you will have to have lathe that moves the metal bar slowly forward and at the same time it's rotating the bar while it's cuting away the growes in screws. The same thing is for nuts only that you drill the hole and need lathe that cuts away material from inside. If you don't have that kind of equipment casting in moulds is alternative.

A conventional machining lathe holds the stock in the rotating chuck, and to cut threads will advance the cutting tool at the appropriate linear to rotational velocity ratio (a standard setup feature on lathes) to achieve the desired thread pitch. This applies to external threads on a screw or internal threads on a nut, except the cutting head would be different or fixtured differently or, taps and dies can be used. The other necessary operations can also be performed on a standard lathe, again with the appropriate tooling.

You were at least conceptually correct. Perhaps you have some experience with a basic woodworking lathe.

However, casting screws and nuts is not at all a viable option in any instance that comes to mind.

You have provided no related information in your question so I will assume you mean "common" screws and nuts in "reasonable" volumes.

Unless you are talking about very large fasteners in small quantities what you are looking for is most likely one or more .... get ready now ........ Screw Machines! (What a coincidence!)

While they have many other uses, Screw Machines, as their name implies are tailor made for your assumed need.

They are a class of (mechanically) automated lathes (typically turret lathes) and are very common, both new and used in a wide variety of sizes and capacities. While the distinction between the newest high end Screw Machines and CNC turret lathes is minimal, traditional screw machines have little or no electronics, relying on gears, cams etc to accomplish the automation. Once setup, (and of course with the appropriate tooling), they are fast and will perform all your needed operations at once, including facing off both ends of the part, from long pieces of raw bar stock which are drawn through the machine as needed, without operator intervention except for oversight, quality control, and replacing and starting a new piece of bar stock (typically in 20 ft lengths). Many machines will accomodate automatic feeders for the lengths of bar stock.

While screws and nuts can (and are for very limited quantities) be made on a conventional lathe, it is very inefficient to do so.

Casting screws and nuts is not an option you even want to consider.

There are many parameters to consider in manufacturing threaded fasteners, such as material, class, strength, rolled or cut threads, tolerances, etc etc., depending on your application or market so you wil have to do some research in that area.

You should be able to find some excellent bargains in used machines because they have been replaced for many other applications by CNC lathes but they are better/faster/cheaper for your application (based on my original assumptions since you failed to describe it).

You just might want to Google "Screw Machine"

If you are interested in high volume manufacture of threaded fasteners, there is one more approach at least.

Cold Headed and rolled threads can be done quickly and cheaply. This approach has been used for a very long time.

Before you start, please read a bit from sources like the Engineers Handbook and actual standards both ISO and US standards. You want to make them to those specs if you plan to sell them.

Steve