Screw Threads and The Threading Operation

Screw threads are an often overlooked and underappreciated invention. This device, an evolution of primitive nail technology, dates back to ancient Greek inventors Archytas and Archimedes as far back as 400B.C. The original purpose was to apply gradual pressure from a crank shaft on olive and grape presses for oil and wine. During this time and for centuries thereafter wooden screws were the norm. Artisans used their skills to produce them by hand, a very difficult and precise operation, until 1797 when Henry Maudslay (1771-1831), an English mechanical engineer became the founder of the machine-tool industry by inventing the screw cutting lathe. This made uniformity in screws and future threading operation technology more than a possibility.

Screws and Standardization

Until Maudslay, manufacturers produced screws with a distinct lack of uniformity in screw threads. The number of threads varied dramatically from manufacturer to manufacturer making any standard impossible to achieve. However, in spite of Maudslay’s work, the situation remained chaotic until World War I broke out. It was during this war that the American National (AN) thread form was established. It remained the standard of all major threads produced in America until World War II.

Not all manufacturers conformed to the AN standard around the globe. During World War II, when American, British and Canadian allies worked on tank and other military equipment construction, issues of compatibility arose. The screws were not interchangeable. These presented problems that the countries did not overcome until following the cessation of the war.

In 1948, a new standard arose. This, agreed upon by many countries, became known as the Unified thread form. It is in universal usage. It also affects what products emerge from the threading operation of a machine shop.

What Exactly Is Thread Turning?

Thread turning is, at its most basic, the production of threads – male or female. It involves the use of such tools as universal lathes and CNC machining. In order to achieve the right thread design, the operator must select the right profile and tool position. In multi-stage thread production, the operator must apply the tool several times at the identical point of the perimeter of the workpiece.

In thread turning, the machinist will also face certain constraints. They tend to be the ones associated with most production and/or finishing work.

• Time
• Budget
• Requested level of precision
• Available equipment

These restrictions may reduce the capability but should not affect the overall quality of work under a skilled machinist.

The Threading Operation

Thread turning is a very demanding form of turning operations. Yet, over the centuries since the invention of the threading lathe, new technology has made the process both easier and less time consuming. In fact, it allows the operator to specify certain aspects allowing him or her to select the type of machining based on whether the thread is to be male or female, external or internal. For a threading operation today, an operator can take advantage of many different thread-machining options to produce an excellent workpiece. JBC Machine is no different. We have highly skilled machinists who can produce consistently excellent threading to exacting specifications. Call us for your next threading project!