We've talked about the types and grades of stainless steel and special alloys in a previous article, but what about the fasteners that can be made from these amazing metals? From the humble beginnings of the screw has arisen a dizzying array of fasteners to meet the demands of modern industries such as aerospace, medical, energy, and semiconductor.
First, a little history. We have the Greeks to thank for the invention of the screw, although Archimede's Screw was actually a water pump. It was a giant screw inside a hollow tube that, when turned, would draw water up. Nevertheless, they got the basic shape right, and by the 1st century people were building olive and wine presses with hand-made wooden screws. This was a time consuming process, and of course no two screws were alike. Then came the Industrial Revolution, which brought the opportunity not only for mass production of screws, but also for standardization. In addition, increased strength became possible with the advent of the metal screw in the late 18th century.
When we think of a screw, we think of the spiral threading around the shank – this is what makes a screw a screw. The head of the screw is (usually) wider than the shank and is the bearing surface for driving the screw. So what's the difference between a bolt and a screw? It can be hard to tell, and is largely a matter of semantics. But generally speaking, screws are tapered and self-threading, and bolts are not; a bolt is tightened or released by torquing a nut, and a screw does not require a nut, but a lot of times these terms are interchangeable and further called out by the varying descriptions and/or part numbers.
The variety of modern fasteners available is mind-boggling. Some of the basic categories of fasteners include machine screws, cap screws, tapping screws, nuts, bolts, flat washers, locking washers, and pins. But within those categories, the possible combination of options is almost endless.
Take, for example, the basic cap screw. It is available with a myriad of heads, including, button head, hex head, socket head, flat socket head and Torx drive; it is available in a variety of widths and diameters; In addition, it might be manufactured to certain specifications (ASTM, ANSI, AISI, AN, MS, NAS, NASM), or made from special materials (18-8, A286, Monel, or Alloy 20 to name a few). See our Stock Items page for just a small sampling of what OSS has in stock – with our line of commercial grade 302, 303, 304 and 316 stainless there are too many to list.
In the modern era, the precision requirements of high-tech industries, such as aerospace and medicine have spawned specialty fasteners. These fasteners are often made from special materials, such as A286 (a favorite of the aerospace industry) Inconel 600, 625, 718 and various other exotic metals.
OSS has been in business for over 30 years. With over 50,000 items in stock, we probably have what you need on hand. But if we don't, we can manufacture it to your specifications. We can take care of stocking programs, vendor managed inventory and more.
More articles from OSS:
From Cutlery to Space Shuttles: The History of Stainless Steel and Superalloys
The History of the U.S. Fastener Industry
An Introduction to Superalloys
A Strong Family Tree: An Introduction to the Grades and Types of Stainless Steel