Bar turning is a mechanical manufacturing process that removes material from a rotating object to create parts with specific shapes. This technique is often used in the production of parts for mechanical fasteners, such as studs, inserts, tie rods and fittings. In this article, we’ll explore screw machining of mechanical fasteners, looking at how it’s done, the materials used and the benefits it offers.
The bar-turning process
The screw-cutting process for mechanical fasteners involves the use of a screw-cutting lathe. The screw-cutting lathe is a type of lathe specially designed for removing material from rotating objects. Workpieces are clamped in a chuck and rotated at high speed. Cutting tools are then used to remove material, creating specific shapes.
Mechanical fasteners are generally made from materials such as stainless steel, aluminum and brass. The choice of material depends on the application for which the fastener is intended. For example, fasteners for corrosive environments will generally be made from stainless steel, while fasteners for lightweight applications may be made from aluminum.
The cutting tools used in the screw machining process for mechanical fasteners can vary according to the shape of the part to be machined and the material used. The most commonly used tools are radial-cutting tools, oblique-cutting tools and threading tools. Radial-cutting tools are used to remove material from cylindrical parts, while oblique-cutting tools are used to remove material from conical parts. Threading tools are used to create threads on workpieces.
The advantages of bar turning for machining mechanical fasteners
Bar turning of mechanical fasteners offers several advantages over other manufacturing methods. Firstly, bar turning enables large-scale production of high-quality parts. Modern lathes are capable of producing parts with high precision and surface finish, which is essential for mechanical fasteners.
In addition, bar turning enables the production of parts at relatively low cost. Bar turning lathes are designed for efficient operation, and can be used to produce large quantities of parts in a short space of time. This reduces the production cost per part, which is important for manufacturers of mechanical fasteners who need to produce low-cost parts. Massard et Cie also uses this low-cost production advantage for small and medium production runs, combining mass production of thousands of studs with production runs of 50 to 100 turned parts.
Bar turning also allows great flexibility in part design. Modern screw-cutting lathes can be programmed to produce a wide variety of part shapes, sizes and configurations, enabling mechanical fastener manufacturers to meet the specific needs of their customers. In addition, bar turning lathes can be used to produce parts to tight tolerances, which is essential for applications where precision is important. Massard et Cie has been certified to the ISO 9001 Quality Management System for over 30 years.
Finally, bar turning is an environmentally-friendly process. Unlike other manufacturing methods, bar turning does not generate excessive metal chips, which reduces the amount of waste generated by the manufacturing process. What’s more, modern lathes are designed to be energy-efficient, reducing the amount of energy required to produce each part. Massard et Cie has been certified to the ISO 14001 Environmental Management System for over 10 years.
The limitations of bar turning for machining mechanical fasteners
Although bar turning offers many advantages for the production of mechanical fasteners, it also has certain limitations. Firstly, the bar turning process can be limited in terms of the shapes of parts it can produce. Parts produced on a free-cutting lathe must be of revolution along the bar axis, which limits the shape of the part that can be produced.
In addition, bar turning can be limited in terms of the size of parts it can produce. Bar turning lathes are designed to produce small to medium-sized parts, which means they are not suitable for the production of larger parts. Even so, Massard et Cie can produce parts over 2000 mm in diameter, from 6 mm to 32 mm, thanks to a fleet of Tornos and Manurhin sliding headstock lathes.
Finally, bar turning can be limited in terms of the materials it can machine. Although bar turning can be used to machine a variety of materials, some materials can be difficult to machine due to their hardness or resistance to wear.
Advantages v/s limitations
Turning mechanical fasteners is an important process in the manufacture of these parts. Modern lathes enable large-scale production of high-quality parts at relatively low cost, offering design flexibility and high precision. However, bar turning can be limited in terms of part shape, part size and the material it can machine. Despite these limitations, bar turning remains an efficient and environmentally-friendly production method for mechanical fasteners.
The different types of mechanical fasteners
To explore this issue in greater depth, we can look at the different types of mechanical fasteners that can be produced by bar turning.
Dowels are cylindrical fasteners with threads at each end, used to secure two parts together. Studs can be made from a variety of materials, including stainless steel, brass and aluminum. Studs are manufactured on a screw-cutting lathe, using thread-cutting tools to create the threads at the ends of the part. They are often used in automotive, aerospace and construction applications. Massard et Cie performs most thread rolling (see thread rolling article) to optimize the strength of the threads thus formed.
Self-tapping inserts are cylindrical fasteners that create strong, mechanical attachment zones on polymer parts thermoformed from a smooth-hole boss. Inserts are generally made from coated mild steel, and are produced using a multi-spindle screw-cutting lathe, with thread milling cutters to create the thread (known as wood-threading or plastic-threading) on the part by polygon turning.
Ties and laces or threaded ends are fasteners used to hold two parts together. Tie rods are made from stainless steel or steel grades 8.8 to 12.9, and are produced using a screw-cutting lathe, with thread-cutting tools to create threads on each end of the part or along its entire length. Massard et Cie uses thread rolling (see thread rolling article) to produce long threads and optimize the strength of the threads thus formed.
Fittings are mechanical fasteners that are used to connect two tubes together, to create a plumbing or piping line. Fittings are generally made from brass, stainless steel or aluminum, and can be fabricated using a screw-cutting lathe to create the basic cylindrical shape, followed by the use of cutting tools to create grooves for the O-rings.
In conclusion, bar turning is an important process in the manufacture of mechanical fasteners. The process enables large-scale production of high-quality parts at relatively low cost, offering great design flexibility and high precision. Although there are limitations in terms of part shape, part size and the materials it can machine, screw machining remains an efficient and environmentally-friendly production method for the manufacture of mechanical fasteners, studs, self-tapping inserts, threaded rods, tie rods, fittings and plugs.
Massard et Cie is the bar-turning solution for all your fasteners. Please don’t hesitate to contact us for further information.