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[January 27, 2020] With the holidays and 2019 now in our rear-view mirror, the ownership and entire team of professional CNC machinists at Advanced Precision Machining (APM) want to wish everyone a Happy New Year and thank our customers for their continued support and loyalty. The milling and machining business is at an all-time high for us, and the hard work of our employees has grown APM into one of the Front Range's premier machine shop operations. Part of this work is dedicated to education and keeping our customers informed with regards to the techniques used in our sector of the precision manufacturing industry through our blog. So, as we reflect upon another successful year of operations and look forward to 2020, we want to take this opportunity to revisit what may appear on the surface to be a seemingly simple procedure we offer as part of our CNC turning services; the various methods utilized for generating screw threads.
When looking at the simple threads on any screw, to the layperson, it might seem as if the machining techniques used in the manufacturing processes are among the least complicated on the machine shop floor. But in reality, due to generally higher cutting forces and tight tolerances, machining screws (aka thread turning), is significantly more challenging. When you factor in the additional demands required of micro-threading, utilized in products such as watches, eyeglasses, cell phones, and medical devices, you’ve upped the workload substantially. Herein lies the difficulties many shops face. From one-off specialty items to mass-quantity production runs, more screw threads are produced in a given year than any other CNC machining element.
While threading is used across many varying industries and takes on many roles, from the large scale down to almost micro levels for custom precision machining projects, every type of thread is ultimately machined to provide specific functions for specific applications. The processes involved in creating a screw thread are varied, encompassing a wide range of subtractive machining, deformative, transformative, and even additive methods. For machine shop owners and CNC machinists, today’s revolution in modern machine shop technology means precise and accurate screw threads can be produced more quickly, accurately, and efficiently regardless of size. What follows below is a brief look at the most common technique; the subtractive method of cutting screw threads.
Bearing in mind that thread turning involves both external and internal threads, with the latter being more demanding, choosing an appropriate application for machining screw threads is based upon the constraints of time, money, equipment, and the degree of precision needed. Subtractive CNC machining methods involve the removal of raw material from a blank, and are universally accepted as the most efficient, cost-effective, and least complex methods to choose from. These include: Thread Cutting, Thread Grinding, and Thread Lapping techniques.
Tap and Die Method
Single Point Threading Method
Thread Milling Method
The precision manufacturing of screw threads can also be performed on a variety of grinding machines utilizing specialized wheels accurately profiled to the desired thread pattern that traverse along the revolving workpiece. Thread grinding is typically used to produce threads to very exacting tolerances, or in extremely hard materials. The most common machine, the universal type, specializes in threading gages, screws, plugs, rings, hobs, and even other threading tools such as taps and dies.
Although the subtractive techniques involved in machining screw threads described above garner the most attention on the machine shop floor and are most commonly employed there, deformative or transformative methods and even additive (3D printing techniques) warrant mentioning. Thread forming, for creating internal threads, and thread rolling, for creating external threads, both involve deforming or transforming the metal used to manufacture screw threads. In short, the threads are formed by pressing a shaped tool into a metal blank, commonly called a 'thread rolling die'. Used in large production runs due to their efficiency, thread rolling/forming dies have the capability to produce one new piece per second and produce none of the waste, or swarf, that’s associated with subtractive methods. Additive manufacturing utilizing 3D printers is gaining increased potential for creating threaded parts, but the technology is not quite where it needs to be just yet. The good news is that further commercialization is on the horizon, and the industry is making some inroads into the dental implant and medical bone screw fields.
Need help with your next threading project, or want to learn more about the range of precision machining options available to you, then contact the CNC machine shop and thread generating experts at APM. Our reputation for quality parts, on-time reliability and exceptional customer service cannot be matched! We're happy to discuss any machining need you have. Call us at at 303.776.1910 or send us an email.
Gerry Dillon is a co-founder, current owner and certified CNC machinist at Advanced Precision Machining (APM), a full-service machine shop located in Longmont, Colorado. Before making his home in the United States in 2000, Gerry was born and raised on the emerald isle of Ireland and took an interest in milling and machining from an early age, ranking #1 in the Irish National Apprenticeship Program. In 2005, he and a partner began what’s grown into a leading Colorado machine shop. Gerry brings over 30 years of machining experience to the shop floor and is certified in all aspects of geometric dimensioning and tolerancing.