If you are a fellow glasses wearer, you probably know the sorrows of losing one of the miniature screws that keep your glasses together. I swear once they hit the ground, those screws are forever lost. I always curse whoever thought to employ minute screws to hold together something meant to help me to see. Screws are apart of the fasteners family. The actual concept of screws can be dated back to 200 B.C. Early screws were a part of the Babylonian Hanging Gardens. Assyrian King Sennacherib used screws as parts of the pumps that fed the water system. Moving up to the first century BCE, wooden screws were widely used in oil and wind presses.
The metal screws that resemble what we are accustomed to today weren’t developed until the Renaissance Age. Between the 14th and 17th centuries, metal screws were handmade. It wasn’t until 1598, when Jacques Besson introduced the first screw-cutting machine. Back then a machine could produce 10 screws a minute, but today that has improved to between 100 to 550 screws per minutes. Mass manufacturing of screws is made possible with cold heading. The cold headed fasteners are then put through thread rolls.
Today, the screw making process is completely automatized. Coil of metal wire is fed into a machine that will flatten and straighten the wire. Another machine will then cut the wire into varies lengths and a one or two punch process die will cut the screw head into its present shape. After this, the screw blanks will slide down a chute leading to one of three types of thread-cutting dies. Well, the threads are actually pressed not cut, which makes the threads stronger and wastes less material.
The first of the dies is the reciprocating die. During this process the screw blank is rolled between a stationary flat day and a die that moves back and forth. A cylindrical die rolls two or three round dies to achieve the same results. Last is the planetary rotary die keeps the screw blank stationary. Several die cutting machines will then roll around the screw creating the threads. I’m not sure if there are any advantages or disadvantages to the three dies, but it seems like they all achieve the same results.