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Helical Cutters Go Deep and Long in Tough Materials

Tim Aydt
By Tim Aydt Indexable Milling Product Manager, Seco Tools LLC

When it comes to achieving high material-removal rates in even the toughest materials, it’s hard to beat helical cutters. With the correct insert grades and cutting data, these cutters can achieve far greater depths of cut than non-helical milling tools without sacrificing reach or the ability to hold tolerance. This means higher rates of metal removal at speeds that reduce the time the inserts spend in-cut, simultaneously minimizing cycle times and maximizing tool life.

For demanding industries like automotive and aerospace, custom helical cutters can transform processes for even the most difficult applications. In materials ranging from heat-resistant superalloys to aluminum, helical cutters can easily outpace non-helical designs and custom versions of the tools can be shaped to perfectly fit the required application. However, demanding industries often have equally demanding schedules, and while custom tool manufacturers strive to meet customers’ needs as quickly as possible, the turnaround time for a custom product can be prohibitive when there are parts to cut.

Despite that disadvantage, there are a myriad of reasons to choose helical cutters. In one example from the aerospace industry, a custom helical cutter used for machining landing gear torque links paid for itself within months. Made from Ti5553, a heat-treated titanium alloy, the part was previously
machined using a high-feed milling strategy that required 84 passes. With a custom helical
solution, that number was reduced to only four passes with a 1.25″ depth of cut.

Given the massive reduction in the number of passes, one might expect a slower process. However, the helical cutter provided six times the tool life of the high-feed mill and a 40% increase in metal removal rate. The end result was a cycle time reduction of 60%, which, over the course of a year of machining, created more than $40,000 in savings.

Aerospace manufacturers have duplicated these results across their industry. Another manufacturer utilized custom helical tooling for producing landing gear truck beams, the critical component that links the axles and holds the brake rods. When compared to the previous solution the company used, the custom helical solution provided 40% increases in speed and metal removal rate. Furthermore, insert wear was much more predictable thanks to process improvements, extending tool life by three times over the previous solution.

This increase in tool life also has significant downstream effects. The time spent indexing inserts or stopping machining for mid-process tool changes obviously drops when tools last longer. This frees a machine’s operator to work on something more productive and reduces machine downtime. Likewise, tooling manufacturers can also offer replaceable end caps with custom helical cutters, which make it simple to replace the front rows of a cutter far more cost-effectively than the alternative: buying a completely new cutter or having the broken cutter repaired.

Seco’s semi-standard range of indexable helical cutters all include replaceable end caps for longer cutter life.

These exceptional results are due in part to insert grade selection—the correct grade ensures the highest possible feed per tooth, a major factor in metal removal rate. F40M, a titanium aluminum nitride (TiAlN) coating, is perfect for inserts cutting parts such as torque links, while T350M, a titanium carbonitride (TiCN) coating, is ideal for parts like the truck beams in the last example.

Grades for Challenging Cuts

Recently, Seco has produced several grades designed for the challenging cutting conditions created by titanium and high-temperature alloys like Ti5553. One newer grade, MS2050, features a niobium nitride (NbN) coating that significantly increases lubricity. Meanwhile, the exceptionally tough MS2500 can reach higher speeds than other grades due to an aluminum oxide (Al2O3) top layer produced
via chemical vapor deposition (CVD), which makes for a wear-resistant grade.

While insert selection plays a critical part in process optimization, the custom helical cutters themselves played a starring role in the examples from the aerospace industry. Conversely, automotive manufacturers rarely need to reach the tolerance levels required in aerospace. Instead, they rely on the cutting geometries of helical mills to reduce cycle times in high-volume applications. With long effective cutting edges paired with aggressive insert geometries and placement, these cutters can even outperform competitors with helical interpolation, ramping and other advanced milling techniques in addition to standard operations.

Semi-Standard Program

For many manufacturers, these advantages mean little due to time considerations; regardless of industry, few shops can afford the time their tooling suppliers need to quote, design, produce and deliver a custom tool. Luckily, Seco has a solution: a semi-standard helical cutter program that streamlines the process by eliminating numerous time-consuming steps. The result is an average reduction in turnaround time of 50%, from over 60 days to as few as 30.

Seco’s helical cutters can achieve high feed rates, large depths of cut and aggressive metal removal, according to the company.

The creation of a turnkey helical cutter solution revolves around semi-standardization. Standard tooling, like any line of standardized products, rarely works perfectly for any given application, but experience has shown what types of tools manufacturers use most often. An optimized process naturally requires optimized tooling, and custom products have traditionally been the only way to achieve these benefits.

The semi-standard helical cutter program succeeds in finding the happy medium between these types of tools. Seco’s program draws on the company’s history of creating custom products to identify a range of helical cutter solutions that its customers most often request. Rather than quote and design each product individually, the program allows manufacturers to receive an instant price quote on well-understood designs, a major factor in reducing lead time.

By starting from a semi-standard design, the rest of the process is much easier to optimize as well. Custom products often require significant time spent on design and subsequent approval, both of which can be accomplished faster when the bulk of the design work has already been completed. Likewise, semi-standard designs make it easier to create optimal cutting programs, allowing for faster production of helical cutters.

Naturally, a semi-standardized line of products cannot serve as a substitute for a fully custom cutter. Your tooling manufacturer should be able to meet these needs with dedicated custom products and process optimization teams, which are capable of engineering complete solutions for complex applications. These services require more time, but these teams can take a deep dive into a process and design a tool around it. For the majority of metal-cutting operations, however, a semi-standard helical cutter will be all a shop needs to positively impact its bottom line—all in less than half the time it took before.

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