Milling Aluminum: Tools to Tackle Industry’s Favorite Switch-Hitter

Of all the metals used in modern manufacturing, aluminum and its many alloys are among the favorites—especially in the automotive and aerospace industries, where they help make vehicles from cars to drones, planes and rockets lighter and more fuel-efficient.

Medical manufacturers, meanwhile, use aluminum for bone saw guides and orthopedic components, electronics makers produce heat sinks and connectors from it, and machine tool builders and other equipment manufacturers prize the versatile metal for pump and valve housings, gear casings, heat exchangers and much more.

Aluminum, it seems, is the switch-hitter of the industrial world.

Tools to Fine-Tune Aluminum Milling

Many reasons for its popularity exist. Aluminum is the third-most abundant element in the Earth’s crust. Depending on the alloy, it has a strength-to-weight ratio several times that of steel. Aluminum is corrosion-resistant, nonmagnetic, thermally and electrically conductive, and 100 percent recyclable. Perhaps most important to manufacturers, the metal is formable, weldable and, above all, very machinable.

That said, care must be taken to avoid several common problems, particularly in milling applications. Without proper chip evacuation, recutting can lead to poor surface finishes and even tool damage. Feeds, speeds and depths of cut must also be appropriate for the workpiece and machine tool in order to avoid burrs, chip welding and premature tool wear.

But as many machining center operators and programmers have found, investing in a top-quality milling cutter helps prevent these issues, spelling the difference between mediocre performance and blowing the doors off of production quotas.

Alex Nguyen, a milling product engineer with OSG USA Inc., knows all about this last part. He provides several recommendations, starting with the company’s AE-N series end mill. “It’s a top-tier option designed specifically for aluminum and other nonferrous materials like copper and bronze, and as with other offerings in this class, it is available in both short and long cut,” he says.

Factoring in Toolpaths, Cutting Parameters

Among the more popular in the series is the TL-N three-fluted long-length, advanced performance end mill, Nguyen adds. Its features include a large core for additional rigidity, a nicked edge on the flutes to break chips into smaller pieces, and a DLC (diamond-like carbon) coating for increased abrasion resistance.

Advanced cutting tool design is only part of the machining equation, however, especially for shops looking to achieve a mirror-like surface finish. As capable as OSG’s and other manufacturers’ premium cutting tools are, the best milling results are achieved with the correct balance of machine tool, workholding equipment and toolholders, as well as properly applied toolpaths and cutting parameters. “It takes the right technology on all accounts,” Nguyen says.

Note the mention of diamond-like carbon coating a moment ago. Machinists reading this might say, “Hold on. Coated tools offer increased heat and wear resistance, but any coating process tends to break up the sharp edge needed for aluminum milling. What gives?”

“It’s shaped kind of like a Christmas tree,” he adds. “Each of the periphery inserts is made of carbide, so this provides increased strength for what is essentially a roughing operation. These sit in a precision fixed pocket and are each designed to remove 70 microns of material, but if one cuts 71 microns and another removes 68, it’s not a problem since the PCD wiper insert comes in last and cleans everything up. This shared approach also allows us to push the feed rates much harder, with a smoother cutting action besides.”

With that in mind, sometimes a super smooth finish isn’t called for. In that case, the M5B90 can be tooled with a “scratching” insert, generating what European automakers call a “frame roughness gasket surface.”

As suggested by the name, this crisscrossed, slightly roughened finish provides a better sealing opportunity for the gasket.

“The finishing cartridge is adjustable to get you exactly the surface finish requirement that’s called for,” Crabtree says. “Given its many advantages, the OEMs are really loving this product.”

What are the biggest challenges you encounter in machining aluminum? Tell us in the comments below.