TPT September 2021

Fluids provide the essential connection for high-quality tube thread cutting By Bob Evans, research scientist at Quaker Houghton’s Metalworking Centre of Innovation

Tubes and pipes are used in some of the world’s most demanding environments, requiring the highest quality of threaded connections. When it comes to maintaining their performance and longevity, Quaker Houghton explains the important role that fluids play in thread cutting operations.

High durability When it comes to oil country tubular goods (OCTG), quality is paramount. From drill pipes and steel casing pipes to tubing, oil & gas companies are reliant on the durability of threaded connections to maintain the integrity of mission- critical applications. Considering the stresses placed on tube and pipe during drilling operations, and the likelihood of remakes during their lifetime, achieving precision and accuracy in the thread is vital. It is no surprise, then, that manufacturers are continuously looking to create ever stronger connections to withstand these extreme conditions – with demand growing in particular for premium class thread connections with enhanced operational and technical properties. These connections require superior screwing properties, to ensure that tubes and pipes can withstand bending and compression loads, as well as high pressure and high temperatures. As a result, threads are typically designed to offer improved tensile capacity, ease of makeup and superior hydraulic sealing. Understandably, the focus is on the materials and the processes that make these advances in thread cutting possible. Yet there is another variable with the capability to make a huge impact on both: thread cutting fluids. Even though tube and pipe manufacturers are familiar with the benefits of cutting fluids, arguably their true engineering value remains underappreciated. It is in the successful triangulation of material, equipment and lubricant that the threading process is most effective. When all work together, the result is a high-quality product and a more efficient and cost-effective operation. The fluid factor is therefore essential, but with so much choice it’s vital to choose exactly the right type and chemistry of the metalworking fluid for each threading application.

Thread cutting fluids Thread cutting fluids serve a number of important functions. By providing a lubricating layer between the cutting tool and the workpiece, they reduce the level of friction and heat generated during the cutting process. The obvious benefits are to minimise adhesion and tool wear while improving the quality of the cut threads, but cutting fluids also serve an important role in providing cooling and heat removal during the process. This function is critical for achieving greater cutting insert life, as well as achieving the required form and dimensional accuracy of the cut threads. A third important function of the cutting fluid is to aid and facilitate chip removal from the cutting area. Not all thread cutting fluids are created equal. The marketplace is literally flooded with oil and water-based lubricants of varying properties and characteristics. The choice of the right lubricant therefore depends on ensuring chemical compatibility, in order to maximize productivity, tool life and efficiency, and to reduce fluid usage. Given their greater viscosities – which tend to offer higher levels of lubrication – oil-based fluids (or neat oils) are typically used in severe and heavy-duty thread cutting operations such as oil and gas pipes. While they are usually highly effective, they often require significant post machining processes such as cleaning, and also can present potential fire hazards during the machining process. Water-based fluids – ranging from clear solutions and translucent micro-emulsions to more effective lubricating opaque macro-emulsion types – are commonly used. Each offers varying degrees of lubrication and cooling properties, and therefore it is important to select and/or engineer the fluid to effectively meet the conditions and demands of the cutting operation being performed.

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September 2021 TUBE PRODUCTS INTERNATIONAL