How to Thread Roll on Your CNC Machine Unattended?

Thread rolling on CNC machines unattended requires a closing scheme to reset the head after each rolling cycle. This is accomplished with a program move that will cycle the closing handle past a fixed point within the machine that will wipe the handle closed. Typically, a program change to the parameters must restrict turret movement to one fixed direction.

Two alternatives exist permitting the tool to close. The first is with a coolant driven attachment. The second locks the tool in a closed position and uses a Roll-On Roll-Off™ strategy. The two attachments achieve the desired result with the coolant closer using elevated coolant pressure available on some although not all CNC machines. The locking attachment can operate on virtually any machine at a significantly lower cost. The two strategies allow the parameters of the machine to remain unchanged and frequently do not add additional cycle time to the process. We are always available to discuss the most practical and cost-effective solution to your application.

What is Roll On Roll Off™ Thread Rolling System?

Technology is constantly evolving. The Ford model T eventually evolved in to the F40 and beyond. Thread rolling likewise is a constantly evolving technology. The tools themselves have become more user friendly and the rolls have improved in performance over a wider range of materials.

New strategies have evolved to reclose a thread rolling head following its popped open stature. Indexing the tool and striking its closing handle on a fixed obstruction was a widely used method. An air cylinder mounted as an actuator was another method. Cleverly configured tension spring devices also had merit. All these methods required limited investment and could exhibit modest failure occurrences.  More recently, a closing device attached to the tool and activated with high pressure coolant seemed to address the earlier issues. While it could only be affective on machines with the required coolant pressure, it too was susceptible to mechanical failure.

Lights out manufacturing can’t tolerate intermittent failure. In a goal to find a constant method to achieve lights out production on virtually every machine configuration, we developed a patent pending device to keep the head closed and utilize a Roll On Roll Off™off strategy. The desired result has had remarkable success. While nearly matching the cycle times prevalent with the older strategies the lack of moving parts has impacted on the physical life of the tool itself. Rotating the spindles during normal pop open operations generate wear on both the spindle and face plate. This resultant wear begins to exhibit itself as taper in the thread form. The new device allows for tool float and keeps the head closed negating wear on spindles and face plates.

Closing strategies and closing device cost are no longer a consideration. Closing failures are no longer a consideration in a “lights out” run time strategies.

Device development was internal to Turning Concepts, LLC. We are presently the single source for the patent pending tool attachment. Do you have an application that could benefit from our development?  Contact us directly for information on availability and cost.

Want To Improve Tool Life Dramatically?

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 1000% increase in basic 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.

New! Patent Pending Attachment

We recently introduced a Patent Pending attachment to convert a traditional pop open threading tool to a Roll-On Roll-Off™ device. When used on modern CNC machines a closing strategy had to be engineered specific to the individual machine. To ease the installation and use, we preset the tool with the correct thread size and installed the device, shipping to our customer ready to install and use.

While this plan yielded the result we wanted to achieve, our customers carried it to another level.  Since the device cannot yield unthreaded parts due to a closing action failure it has become a “lights out” device for some customers permitting them to run unattended.

When thread rolling, the tool controls the pitch diameter and the minor diameter. The major diameter is a function of the blank diameter controlled by the cutting tool within the machine. Even with a class 3 thread form the tolerance on the major diameter approaches .010. This generosity of tolerance permits longer tool life of the carbide turning inserts. When bidding for work in a typical job shop atmosphere cost per piece becomes the catalyst for winning the bid. Running unattended removes the direct and indirect labor cost associated with manned operation. The resultant cost reduction filters down directly to cost per piece and profit margin. This can often be the difference between winning or losing the contract bid. CNC machines contain canned programs that can be directly applied to the new threading strategy.

Roll threading is a single pass process that typically can produce a high-quality thread at a rate of 1 inch of thread per second of cycle time. Roll-On Roll-Off™ off doubles the average cycle time but frequently is accomplished within the same time frame as rolling on, popping open, rapiding off and reclosing the head for the next part. While we knew we had a device that was revolutionary, our customers are exhibiting even more profound application techniques. Using the “phantom” operator during off hours and continuing uninterrupted production while improving tool life has given added meaning to product improvement. Can this strategy improve your production process? Contact us and let us help with your application!

Thread Rolling Generates Cost Advantage

For too many years rolling threads on metal parts was considered a “black art.”  And, indeed, depending on the individual circumstances, it was. Bump rolling was a popular method used on a variety of screw machines. It required precise knowledge of the application and careful design to achieve success. It was indeed a “black art” used exclusively by knowledgeable screw machine set up people. A broad variety of attachments began to appear on the scene dedicated to screw machine use. Ease of set up varied by manufacturer but none were simple. All required careful attention to set up requirements.

More recently screw machines have begun to give way to CNC machining. While threading can be accomplished on a CNC machine much easier than previous set up intensive screw machines, roll threading can be an even greater value to a CNC application.  Thread strength improves dramatically, and cycle time decreases dramatically. Frequently roll threading will impact so greatly on part cost that the shop utilizing rolling will have a significant cost advantage over a competitor. In a job shop atmosphere this can make the difference in winning versus losing a bid. Tool design has improved to make installation of some tools far easier than previous designs. Design continues to evolve, and applications continue to become easier to install and use. We strive to supply our customers with simple, easy to apply, instructions. Tooling is typically supplied with instruction well beyond that of the manufacturer.  Our advice and support provided with every sale minimizes the potential for mistakes. Our primary goal is to make every thread rolling customer a knowledgeable confident user.

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.

Which Threading Method is Most Cost Effective?

In the real time world of contract manufacturing, picture your company landing a contract to produce 80,000 threaded stainless-steel connectors. The specified thread detail calls out a class 3 aviation thread. You could choose to single point, chase, or roll the threads. Would either option impact your bottom line? ABSOLUTLY !

Single pointing will likely produce 100 threads per cutting edge of the insert used. From the first part to the final part per edge, insert wear will allow drift in the minor, pitch and major diameter. It may introduce the need to deburr as well as require 10 or more passes to complete each thread.  Cycle times for threading will likely exceed 10 seconds per thread. Indexing the tooling every 100 pieces adds cumulative down time. While the insert cost is relatively low, cycle time and down time add significant cost to the final product.

Chasing reduces the cycle time but also has the potential for burr creation as well as the need to regrind chasers.

Rolling will yield as much as 100 times the volume of threads without a tooling change. Rolled threads will never require deburring. The minor diameter and pitch diameter of a rolled thread are a function of the roll design and will never waiver. The major diameter is a function of the blank size but since the major diameter of any class of thread is typically an allowance of .010 normal turning tools will see extended life.

Cycle time will be on an order of 1 inch of completed thread per second of cycle. This is typically 10 times faster than cutting the thread. The tensile strength of the rolled thread will typically double from the stated tensile of the raw material. Servicing the tool with roll replacement can be done in minutes on the machine. Since labor cost is the largest factor in determining the overall cost of each part, cycle time to produce the part and service time to renew and replace tooling are the biggest factors in calculating profitability. Understanding these circumstances makes thread rolling the obvious choice for maximizing profitability. Rolling yields the highest quality product in the shortest possible cycle time. Cycle time and profitability are codependent.

Leaded Fuels, Spark Plugs and Thread Rolling

Rolling threads on various materials became a necessity in high volume manufacturing in the US following its discovery in Germany after the second world war.

The most dramatic effect was in the production of spark plugs. In the US alone, more than 10 million spark plugs were being produced daily by several manufacturers. Leaded fuels were necessary to lubricate engine valves but subsequently fowled spark plugs limiting their useful life to about 10,000 miles. When lead was outlawed in motor fuels in the 1970’s hardened valve seats became the standard and without lead fowling spark plugs, spark plug life increased more than 10-fold. This reduced product demand 10-fold. Thread rolling migrated from multi spindle screw machines to modern CNC machines for the very same reasons.

Cold forming of threads became equally important in lower volume production from a time and cost consideration. Threads can be formed typically at 1 inch of thread per second of cycle time. A cold formed thread has greater yield strength and surface quality than a cut thread. Many materials that are difficult to cut are easy to roll. Time cycles and part volume create significant value in throughput cost. This value impacts on the final cost of the finished product.

In a job shop atmosphere, it can be the strategic difference between winning the quote or losing the work to a lower bidder. Rolled threads can reduce the effects of corrosion improving life cycles in many applications. The relative ease of applying this technology to today’s metal working machines makes it even more important as a value-added component of the modern machine shop.

We can evaluate your part, your process and your machine when applying the application of thread rolling to your operation. Thread rolling was once conceived as a “black art” but is truly a straight forward application driven technology easily applied in any modern machine shop. Many military and aviation components demand rolled threads for strength and surface quality. Let us help with your application.  The cost implications can be the leverage your company needs to improve profitability.