6 Questions to Ask BEFORE Running a CBN Hard Milling Test

By Chad Miller, Product Manager-Advanced Materials

Hard milling can be tricky. But if applied properly, you stand to benefit more from this machining practice than if you were using grinding, wire EDM or die-sinking EDM methods. Not only are grinding and EDM machines more costly than milling equipment, they also require a lot more set-up time. When compared to grinding, hard milling can reduce your cutting time by up to 60 percent.

To successfully hard mill a component, the right machine tool, spindle, CNC control and CAD/CAM system are critical to your operation, but even more important is choosing a high-quality cutting tool and having a clear understanding of how to effectively implement it into the machining process. When I’ve seen manufacturers fail at hard milling, it’s usually because they skimped on cutting tools. It’s common; they just don’t realize the right choice early on can help save them money in the long run.

CBN cutting tools are ideal for rough and finish machining of hard steels up to 70 Rockwell as well as abrasive materials, such as grey cast irons. CBN is harder and more abrasive resistant than the carbide and ceramic inserts that are commonly used. CBN costs nearly seven times more than carbide, but users greatly benefit from its adequate balance of strength, toughness, thermal conductivity and chemical inertness.

Here are six questions to ask yourself before making your cutting tool selection and moving forward with a CBN milling test.

1. “What material am I machining?” CBN works well in all types of hard materials, including high tensile steel, high speed steel and white cast iron; soft/abrasive material such as grey cast iron; and difficult to machine materials such as nickel-based and hard facing alloy. However, CBN does not work well in applications involving soft steels or nodular irons.
2. “Will this require rough or finish machining?” Determine whether your hard milling operation will involve rough or finish machining because knowing this helps in selecting the right insert and cutter for the job.
3. “What’s my approach angle?” Another factor that impacts cutter selection is the approach angle; therefore it’s important to decide whether square shoulder or face milling is the best choice.
4. “What is my cutter geometry and setup rigidity? Answer this to determine whether a positive or negative cutter works best in a particular application.
5. “Will I need a wiper insert?” Positioned slightly higher than other inserts, wiper inserts “wipe down” the part to create a superior surface finish. Need a porous finish? Don’t use a wiper insert.
6. “Does every pocket of my test cutter need to be loaded with CBN?” With the high upfront costs of using CBN, you should take steps to ensure you don’t lose a significant amount of money during your milling test. For example, the test cutter does not need to have every pocket loaded with CBN. An effective test can occur with only one or two inserts and an adequately adjusted feedrate. 

Hard milling know-how is vital to its successful implementation and your future productivity and profitability gains. If this is a machining practice you are really considering, but are unsure of where to begin, don’t be afraid to ask for assistance.

An OEM partner that specializes in hard milling tools, such as Seco, can assist you in selecting the best tool for your job, develop a proper cutting strategy for your application and recommend proper feeds and speeds, depths of cut and programming for your cutting material.

About the Author

Chad manages Seco's advanced materials product lines, including all CBN and PCD products. When he's not helping customers implement advanced metalcutting solutions, you can find him training for and running 5K, 10K and 1/2 marathon races and triathlons. Chad can be reached at cmiller@secotools.com.

Improving Your Process With A Process Cost Analysis

By Earl McMann, IKA – Strategic Account Manager

Over the past decade, process optimization has gone from an ideal to a necessity. Your customers need product faster, and they want it cheaper. The competition, both at home and abroad, is constantly looking for the opportunity to beat your turnaround time or price. If your operations are running at less then their full potential, you’re surrendering an advantage that can have a substantial effect on your long-term profitability.

When pursuing process improvement, one of the first considerations needs to be defining the desired outcome. The final objective is nearly always long-term maximization of profits, but companies often set short-term goals at odds with this mission. For instance, it’s common to encounter a situation where a team has been tasked with minimizing a specific cost, such as tool spend, without looking at the larger picture of overall profitability. In these cases, achieving the current goal can actually be detrimental to overall success.


As a not-entirely-hypothetical example, consider a shop that reduces its tooling cost per component by 25%, by switching to cutters that provide lower performance. On its face, this can look like a win, but there’s always a trade-off. Instead of producing 75 components per hour on a machine, output for the shop may drop to 65 components per hour. Such a loss in productivity can wreak havoc on profitability. Fixed costs, such as the machine, facility, etc., actually increase per component when efficiency suffers. The same goes for labor rates per component. Not to mention that the reduced productivity can introduce or worsen a bottleneck and limit overall capacity. In many instances, spending more on tooling, a machine or other equipment actually reduces total cost.


With the goal of total cost reduction in mind, a team or individual dedicated to process improvement must decide where to focus their efforts. If no problematic applications immediately emerge as obvious candidates, a basic analysis of workflow can help provide direction. Identifying machines or cells that are bottlenecks or consistently operating at or near full capacity will almost always offer up a good starting point.


Once an application has been targeted, the real work begins. Extensive information should be gathered and analyzed, both on the current process and on available alternatives. At this point, collaboration with your suppliers will often spell the difference between improvement and true optimization. No one will understand the machine, toolholding, cutters and other equipment in the process better than those companies that developed them. Involving representatives from these suppliers in your efforts will bring together a level of expertise that’s impossible to practically maintain in-house.


Following comprehensive analysis of options for improving a process, your team should test out the chosen solution and make sure it delivers the expected results. If it does, an implementation plan should be incorporated that includes training of your operators and other team members who will be affected by the change. This ensures your organization gets the most out of the hard work you’ve put in.


To offer assistance to our own customers’ process optimization efforts, Seco developed the PCA (Productivity and Cost Analysis). This program brings a formalized and proven approach to gathering and analyzing data, comparing and testing potential new solutions and then making a recommendation based on hard documented results.


If you have any questions pertaining to process optimization or would like additional information on Seco’s PCA, please feel free to contact me at emcmann@secotools.com.

About the Author
Earl works closely with Seco’s larger customers to find ways to improve the productivity and cost-effectiveness of their operations. When not on the clock, he enjoys spending time with his wife and kids, as well as fishing, hunting and golfing.