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
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.
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
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.
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
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.
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.
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.
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.
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.
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
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.
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.
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!