Two of the ways of creating threads on mechanical fasteners are rolling and cutting. Roll threading is widely accepted as the fastest and preferred method of producing uniform, smooth, precise threads of superior physical qualities.
What Are Rolled Threads?
Thread rolling is a process wherein, much like forging, a metal is forced into itself using mechanical forces driven by precise tool geometry and hydraulic pressure. As opposed to cutting threads, thread rolling does not remove material from a workpiece, but manipulates it to create the contours of a given thread form.
This cold-working process not only saves cost by eliminating the scrappage of material as compared to cut threads, but it also imparts a smooth, work-hardened exterior which makes fasteners stronger and longer-lasting. Unlike cut threads, the material grain structure is not severed during the threading process.
Much like forging, cold-working a steel alloy will change its physical characteristics. The material is strengthened by using large forces to compress the steel into itself, forming a layer on the exterior far tougher and harder than that of its core. This difference of physical characteristics is called anisotropy, and it directly influences the mechanical properties of the workpiece that has been cold-worked.
The mechanical properties of a material are highly dependent on its crystalline structure. Metallic bonds group crystallites to form a grain. Grains of differing size, shape, and direction of flow, known as polycrystalline structures, are propagated during the cooling process of steel after smelting.
These polycrystalline structures permeate the entire body of the material before being cold-worked. Forming the metal, as in the case of thread rolling, causes its grain flow to align with the direction of the force cold-working it. The crest and root radius of a rolled thread are made to be denser and stronger as a result of this action.
Types of Thread Rolling
There are two types of thread rolling: infeed and thru-feed.
- Infeed: Used for general rolling of parts up to the maximum length of dies and also shouldered or headed workpieces
- Thru-feed: Used for rolling threads that exceed the maximum face width of the dies, as well as for continuous rolling of long threaded bars
Industries That Use Thread Rolling
There are many industries that benefit from thread rolling, including:
- Machine center manufacturing
- Marine manufacturing
- Hydraulics manufacturing
- Oil and gas
- Lifting mechanisms
- Food processing
- Tooling manufacturing
- Aircraft manufacturing
- Medical device manufacturing (bed lift)
- General use
Why Are Rolled Threads Superior to Cut Threads?
Benefits of Rolled vs. Cut Threads
Even though modern thread cutting has been a standard metal fabrication process for hundreds of years and is still the preferred method for certain jobs, the thread rolling process provides various benefits for different industries and can be a viable alternative to traditional thread cutting.
- Material Saving: The diameter of the blank is between the major and minor diameters of the threads, and varies with the material, type of thread, and thread specifications.
- Strength: Rolled threads maintain grain structure in continuous, unbroken lines following the thread profile, increasing tensile and shear strength, as well as hardness.
- Improved Finish: The smooth flanks of rolled threads provide better surface contact with mating threads so burnished roots and flanks are free from chatter, tearing, and cutter marks.
- Superior Quality and Accuracy: Compared to cut threads, which rarely fall below a 63 microfinish, rolled surface finishes will be a 32 or less. Additionally, thread rolling is unique in its ability to maintain the accuracy of the original setup during long runs of high-speed production.
Enjoy the Many Benefits of Roll Threading
Interested in roll threading for your application? Keystone Threaded Products produces top-of-the-line, USA-made, unsurpassed parts that are recognized industry-wide for their quality, including Acme threaded products, metric threads, trapezoidal threads, and unified threads.
Whether thru-feed or infeed, we can form threads on your components at a pace unparalleled by conventionally machined cut threads. Our thread rolling machines use a constant hydraulic force at high pressures to ensure the form of any thread we make is fully realized. This cold-working process not only saves cost by eliminating the scrappage of material as compared to cut threads, but it also imparts a smooth, work-hardened exterior which makes them stronger and longer-lasting.
Our team is dedicated to meeting your project’s specific requirements. We have the knowledge, skill, and proficiency to manufacture the highest-quality precision roll threaded and machined products that are integral to your design.
With added strength, the cost savings of efficiency, and material maximization inherent to the process by which they are made, precision roll threaded products are the best choice for many applications.