The New Rules of Cutting Tools — Rule #3: Diamond Shouldn't Be Rare

Diamond and diamond-like cutting tools, whether polycrystalline diamond (PCD), cubic boron nitride (CBN) or diamond-coated tools, will increasingly figure into advanced machining applications. The share of cutting-tool applications filled by these tool materials will continue to grow.

This is inevitable, says Jim Graham, machining products manager for Diamond Innovations. Developments in PCD and CBN have allowed these materials to improve in ways that make them more versatile and cost-effective. Meanwhile, the machining speed and tool life of these tools continue to take machining processes to levels of performance where carbide cannot go.

In fact, diamond and related tooling figure into the two previous new rules of cutting tools—“Do More With Your Machine” and “Demand Application Expertise” (see www.mmsonline.com/newrules). Through long tool life and fast cutting parameters, the tools increase machine capacity by reducing the frequency of tool replacements and allowing machines to make parts at a greater rate. Meanwhile, the tooling increasingly figures into expert solutions tailored to more demanding applications in various industries.

Here are examples:

High-Performance Parts

In automotive production, the move to higher performance car engines is creating a push toward materials that are more difficult to machine. Intake and exhaust valve seat rings are increasingly made from exotic alloys. Other engine components are being made from compacted graphite iron (CGI). Even the increased demand for common cast iron parts is having an effect, because fresh castings are so much more difficult to machine than castings that have had time to age. In automotive machining challenges like these, CBN cutting tools have proven to be the answer.

However, aerospace production may provide just as great an opportunity for gains in productivity through sophisticated tooling. New aircraft designs will create significantly more demand for machined titanium, including composite-titanium materials. The demand will be so great that shops will not be able to keep up using their existing machining processes. To increase capacity, many shops will have to process parts faster by increasing their speed. In the right applications, diamond cutting tools and coatings can allow these shops to run much faster in titanium.

Drilling Composites

Yet another aerospace application of diamond goes beyond literal “metalworking,” because it relates to the composite materials that are increasingly taking the place of certain metal parts. Drilling expert Precision Dormer sees the machining of composites as one of the key areas where diamond tooling, among other high-performance tools, can significantly improve production efficiency.

Gary Kirchoff is the company’s product manager for composites-related tooling. He is careful to note that not every drilling process has the rigidity, stability and/or low runout necessary to allow diamond to work well. The company continues to develop drill designs tailored to various levels of composites machining equipment, from hand-fed drilling units to the most sophisticated CNC machines.

However, when diamond-coated or PCD tools can be applied to drilling composites, the cost and productivity improvements can be striking. Because carbide tools in abrasive composite materials wear quickly, diamond tooling can provide many times more life. It can also machine so much faster that hours per part can be saved from workpieces requiring numerous holes. In fact, the same diamond tooling can continue on into drilling certain metals, allowing the diamond tools to perform efficiently in assemblies involving composites/aluminum or composites/titanium stacks.

Applying Diamond

However, not every metal or every material is right for PCD, CBN or diamond-coated tools. In addition to the aerospace composites, appropriate materials include titanium, aluminum and hard steels. The machine tool also has to be suitable, because this tooling has a need for speed. Slower machines may not be able to realize all the value this tooling delivers. There is a need for rigidity, too, though the machine may not have to be as rigid as many believe. The toughness and resilience of these tool materials have improved considerably in recent years.

Finally, diamond tools and related tooling often favor particularly long cuts or large machining volumes. The reason for this is simply the life of the tooling. The tool life can be so long that it can take a lot of cutting just for the shop to capture all of the useful life the tool can deliver.

How do you know whether your shop can benefit? Mr. Graham says the aerospace titanium example offers a clue. Simply put, look to where your capacity is limited compared to the demand your shop is facing. In the parts of your process where you simply must accommodate more orders or achieve a greater output, CBN or PCD tooling can allow you to realize these productivity goals by increasing your speed, instead of having to buy a new machine.

Next: Rule #4 - Focus on the Biggest Sources of Expense