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.

From Bump Rolling to Modern Rolling Techniques – Thread Rolling

The earliest form of producing a rolled thread came from a technique called bump rolling. This utilized a single roll that pressed the form into the material with side pressure. While it was the original approach to rolling threads it certainly earned the craft the nick name of “black art”.  It took painstaking effort to achieve set up success and was helped by the wide use of soft leaded steels. Set ups were best done “When the moon was in the seventh house and Jupiter aligned with Mars”. Despite its perils it could be productive and most certainly became the catalyst for developing more robust attachments and machines.

Further development brought about robust mechanical devices that could be pneumatic or purely cam driven. Few of the early devices could be used easily on modern CNC equipment but remain in use today on multi spindle automatic machines. Pneumatic devices require dry filtered air for best performance. Pneumatic delivery systems during high humidity days are notorious for compressing water out of the air and fouling the operation of the tool resulting in sketchy tool performance.  The pure mechanical devices are unencumbered by humidity.

Today’s materials with the removal of lead from most manufacturing have created a new set of demands on the tools and machines that frequently demand rolled threads for quality and economy. Virtually all machine applications have one or more tool selections available to achieve an economical end result. Review your application with us. We can recommend one or more solutions to your specific needs.