If Thread Rolling Doesn’t Excite Manufacturers, What Will?

For many CNC applications thread rolling is the best choice for creating higher quality external threads in one pass without chips. The technology has spanned years on multi spindle machines, engine lathes and dedicated thread rolling machines. CNC machines can particularly benefit from rolling technology in dramatically reduced cycle times with equally dramatic thread quality improvement. Single point threading on a CNC machine has an advantage when parts production volume is small. This advantage disappears when volume increases. Frequently even in low volume production, rolled threads are specified by the end user due to the quality issue of the threaded part.

Aviation and military parts are frequently specified as a rolled thread regardless of lot size. The technical advantages of a rolled thread are dramatic. Since rolling is a cold forging process it yields no chips and typically requires 90% less cycle time to produce a thread. The rolling process creates much higher yield strength in the material as well as far improved surface finish. These characteristics have made the process important in today’s automotive plants. Rolled threads exhibit higher strength, greater wear resistance, greater corrosion resistance and greater galling resistance. Qualities desired by automakers to minimize warranty failure. Valve stems are an excellent example of a threaded part that benefits from corrosion resistance. A rolled thread maintains better accuracy from part to part than a cut thread simply by removing the wear aspect of a cutting tool that allows cut dimensions to drift. Consider an automotive application that uses a single point machine cut thread in a blazing 4.8 seconds of cycle time. We can all agree this machine time is impressive but let’s roll the thread with a radial head in 0.2 seconds.

Can 4.6 seconds per piece in cycle improvement impact cost over 5 million parts?

Can better part quality with lower recall potential excite a manufacturer?

Most external threads regardless of description can be rolled. Most materials, even the difficult to machine, can be rolled with ease and efficiency. Unlike cutting, tool changes decrease dramatically with rolling. This adds yet another dimension to cost savings by reducing time for insert indexing. While you currently are not building space stations, supersonic aircraft or nuclear submarines if your rolling threads your sharing their technology.

It Started with the Wheel and Later Led to the Telephone and Electricity

It started with the wheel and later led to the telephone and electricity. Invention and discovery continue to change the face of our world as we know it. Thread rolling developed in the early twentieth century and has mostly remained constant since its invention. While difficult materials can be rolled the life of the rolls themselves are limited when compared to mild steels. Nitriding was one means of improving roll life and reducing part cost but also had marginal benefit. Recently a new method has emerged that has shown the ability to improve tool life dramatically. It requires secondary processing of the basic thread roll that adds time to delivery as well as an increase in roll cost by 50% to 70% above the cost of the manufactured roll but the results can be staggering.

We presently have a customer running 17-4PH Stainless Steel that is achieving a 1,000% increase in basic thread roll life. The cost benefit is dramatic, the downside for us is a 10-fold reduction in roll sales to this customer. We pride ourselves on our attention to technology and the goal of being the most valued supplier our customers do business with.

The new technology to improve wear resistance on thread rolls can probably be used on any part that sees friction wear as a failure mode. We can offset our thread roll sales loss by employing the technology into other tools not presently strong in our sales forecasts. Parts that fail due to friction, gears, wear plates, hobs, mold and die plates as well as a multitude of other components could well be strong candidates for improvement. Is friction a contributor to your tooling cost?  Contact us, we would like to offer a solution and allow you to speak with our end users that are on the cusp of dramatic change in threading cost.

Which Materials Thread Roll Well?

While we often extol the various attributes of cold formed (rolled) threads, the materials that can be rolled are seldom outlined in broad terms.

Steels are virtually all roll-able. Included in the steel family are Structural, Case Hardening, Nitriding, Free Cutting, Heat Treatable, Tempered, Tool Steel, High Speed, Stainless, Cast Steel, Malleable Iron and Cast Iron with an elongation factor greater than 8%.

Rollability is also practical in Copper, Copper Alloys, Zinc Alloys, Aluminum Alloys and Titanium Alloys. In addition, Nickel, Monel, Hastelloy, Inconel, Waspaloy and Titanium are also good candidates for rolling.  

The principle deciding factor in the ability of any material to cold form (roll) is an elongation factor greater than 8 percent. As can be seen by the listing many of these same materials are difficult to machine and tough on tooling. Roll life varies throughout the variety of material applications but cost per thread is always an advantage rolling has over cutting.

The tensile strength of a rolled thread will increase from about 40% to as much as 300% in some materials. The tensile strength improvement makes rolling highly desirable in military, aviation and automotive applications. Marine applications using Nitronix 50 and 60 are especially suited to rolling. This is a material with notorious work hardening ability.

We can predict with relative accuracy if your material is a good candidate for thread rolling. Does it conform to the materials we’ve outlined and is the hardness less than 40 on the Rockwell C scale? If you’re processing one or more of these materials daily and not rolling but cutting your threads you’re adding cost and lowering the quality of your finished product.