Thread Roll Leads Explained by An Expert

Rolling screw threads in metal is the most cost and quality effective method of producing threaded parts. Three basic thread production technologies exist throughout the metal working world. Axial tools produce one thread with each revolution and have no length limitation other than the potential stroke length of the machine the tool is mounted on. The tool design utilizes a roll that requires a soft lead to start the metal deformation leading to a finished thread form. Depending on the roll lead the part will exhibit 1.5 or more unfinished thread forms at the end of the part. The harshness or softening of the lead has a direct impact on overall roll life. Despite the unfinished thread characteristic, it is possible to gauge to a shoulder using an undercut behind the thread body to clear away the unfinished thread portion.

Fette thread rolls are designed with different lead designations labeled .6K, 1K, 2K and 3K.

0.6K lead roll leaves 1.5 unfinished threads.

1k lead leaves 2 unfinished threads. 

2K lead leaves 3 unfinished threads

3K lead leaves 4 unfinished threads.

Both 1K and 2K lead rolls are considered standard and priced accordingly. A .6K and 3K lead roll set are considered “special” and are premium priced.

Is there any advantage to running lengthy leads?  OF COURSE!  A 2K lead can add 20% to roll life in many materials. A 3K lead is frequently used in the oil patch industry and the additional unfinished threads have no impact on the performance of sucker rods as an example. Cost and availability of rolls often become the driving factor in tool selection as well as part design. Applying the best roll selection can impact on overall cost per thread but part design is frequently the driving force behind roll selection.

When thread design commands very short threads or little to no relief, axial thread rolling is not the best option even though axial rolling is always the lowest cost tooling option.

Cut Threads Vs. Rolled Threads

The creation of screw threads began several centuries ago, as a cutting technology. It was first used in wood applications and as cutting materials improved, metal applications. With the advent of more powerful machinery, rolling threads on various metals became possible. The ductility of most metals lead to the discovery and development of thread rolling technology. Each technology had benefits that were strongly influential in their direct application.

Cut threads require lower horsepower to be successful and could be used in materials with little or no ductility. Most threads up to 2″ diameter are easily rolled on most manual and CNC machines, both horizontal and vertical. Mechanical requirements are easily calculated. A one-inch length of a cut thread can be completed in many materials in 10 seconds. Difficult materials require more passes and more cycle time. Rolled threads can be completed at a rate of 1 inch per second of cycle time. Difficult materials pose little if any additional cycle time requirements. Cut threads create sharp, bright finishes and are without question prettier than rolled threads.

Rolled threads produce radiused root and crest of the thread and exhibit at least a 40% increase in tensile strength over a cut thread. Rolling a thread redistributes the grain of the material while its cut thread cousin cuts across the grain. Cut threads will always win a beauty contest over rolled threads but will lose in overall quality comparison in all roll-able materials. In many of the more difficult materials to cut, rolling can increase tensile strength by as much as 300%. Cut threads in corrosive materials will always corrode at a more rapid rate than a rolled thread with burnished flanks. Many applications that specify rolled threads only are taking advantage of tensile improvement and corrosion qualities.

Roll cost as a ratio of parts produced versus insert cost per parts produced, rolling will always win the overall tool cost comparison. All thread classes can be cut or rolled. If your part cost can be improved by shorter cycle time and improved tensile strength, thread rolling may be your single opportunity to garner bid work in a job shop atmosphere. Challenge us to help you find the best cost and quality to improve your winning bid ratio.

Make America Great Again!

Our shared victories with our allies in two world wars made us recipients of several technological discoveries. Following the end of WW2, jet propulsion and rocketry were only two of many technologies to migrate to America along with many of the scientists and engineers who developed them for our enemies.

Rolling of external threads in metal became one of the technologies we garnered from Germany. National Acme Machine Company in Cleveland Ohio developed a joint venture with the Willhelm Fette Co. in Germany to market and use thread rolling attachments in their multi spindle production machines. James Abbott from NAMCO became the US point man for the joint venture. As time moved forward, NAMCO was acquired by the Cleveland Twist Drill Co and they made an internal decision to copy and produce the thread rolling tools being imported from Europe. This led to the development of Fette America and the product from Germany imported to the American market. Jim Abbott became their technology manager for their American market place.

Since the disillusion of the joint venture, the American made product changed ownership several times but did not evolve. The German product on the other hand continued to evolve with many strategic changes implemented to allow the device to be used on modern CNC equipment as well as multi spindle machines. The product continues to evolve today and Turning Concepts (TC) has taken an active role in the evolvement. TC has developed an attachment for axial thread rolling heads that permits a roll on roll off strategy taking advantage of the canned cycle programs of the typical CNC machine. Patent applications are processing while implementation is in progress.  Rolling heads are being preset and shipped with specific instruction that typically allow installation with first piece acceptance. We at TC prefer to lead with a technology we understand and can apply with confidence. Let us help by sharing our experience and implement a solution to your manufacturing demands.

Thread Rolling is NOT that difficult. If you think it is, we’re here for you!

There used to be an old saying “You can lead a horse to water, but you can’t make him drink.” For too many years this saying could easily apply to thread rolling technology. For too many potential users it seemed too complicated, too difficult to understand. It was thought the tooling required could only be applied to multi spindle screw machines. The reality is it can be relatively simple to apply and even more appropriate to install on modern CNC equipment.

We have been involved in the application and development of thread rolling attachments for more than 50 years. Application knowledge and service have been the core strength of our organization servicing North America’s thread rolling users. We indeed cover North America and despite our location in the Eastern Time Zone, we service customers in the Central, Mountain and Pacific time zones as their workdays unfold. Our application engineers routinely monitor their phones daily. Accepting calls from end users throughout North America as their time dictates. Precise knowledge and dedicated service make our organization the “go to” people for thread rolling technology. Certainly, we want to sell thread rolling products but more importantly we want to support your threading applications. Knowing your threading history and machine applications give us confidence in your repeat business and provide you with the confidence to expand your application. Contact us, we’re eager to provide you with contact names and phone numbers of our people that can be your mobile guide.

Save Time and Money Hollow Milling.

The critical costs involved in any manufacturing endeavor always include time, materials and overhead. Most frequently we strive to control material and tooling costs as our best solution to control product cost. Time is usually the highest cost involved in manufacturing any product. We like to believe we have focused on this aspect by using state of the art machines and tools. A real example is the use of modern CNC lathes and mills to turn and mill intricate metal parts. Single pointing with carbide inserts and computer control appear to maximize the efficiency of today’s machines.

An old but still very effective technology is hollow milling. This can be done on any CNC machine. Normal turning operations that utilize single point turning with multiple passes can be achieved with an indexable hollow mill using several inserts in one pass. Often much longer turned lengths can be achieved without dreaded push off.

How much return can be achieved with an operation that reduces several seconds of cycle time is an easy calculation. Have you run turning cycles over 10 times diameter unsupported?  WE HAVE. Furthermore, we have the modern indexable, cost effective tooling to achieve results that are driven directly to the bottom line. Threaded forgings probably represent a product with the highest return but virtually any machined product can benefit from hollow milling.

Let us review your product and suggest our approach at reducing your manufacturing cycle time. The results can be rewarding. The investment is minimal. We can share several cases where the application of hollow milling helped a customer land a manufacturing contract from their competition through inventive tooling applications.

Want to Thread Roll on a CNC Machine?

Fixturing a thread rolling head in a modern CNC machine can be enhanced with the addition of a fixturing flat on the shank of the tool. The present design of the modern EVO style Fette thread rolling tool can be effectively anchored by machining a flat anywhere on the 360-degree circumference of the tool. This is effective due to the ability of configuring the closing ring in to any position required.

The multitude of older tools that were designed with a fixed closing handle had to be carefully positioned to identify the accurate location of a fixturing flat. Without a fixturing flat on the shank, it was probable that the tool could spin if something went wrong with the process. This in turn could lead to a collision problem and probable tool breakage. Machining a flat from the manufacturer was not possible since it was unclear where and on what machine the tool would be installed.

We can help with strategies to fixture the tool accurately once we know the machine detail. Contact us for processing assistance.

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!