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Introduction to High Efficiency Milling

Updated: Feb 13

High efficiency milling is a metalworking technique that helps spread wear of a cutting tool across the cutting edge, dissipate heat, and reduce failure. High efficiency milling cutters such as solid carbide endmills have a greater number of flutes and a strong, heavy core. But what makes this technique so advantageous?

Over the past 10 years or so, the strategy of high efficiency milling (HEM) has been gaining popularity in the metalworking industry. Many of the CAD/CAM software packages in the market come with modules to accomplish this effective milling strategy. Depending on the software your company uses, HEM can also be known as Dynamic Milling, High Efficiency Machining, etc.

High Efficiency Milling vs Traditional Milling

High efficiency milling is based on the “radial chip thinning” theory to keep the tool cutting at an ideal chip load. This strategy is designed to increase metal removal rate with a substantially lowered radial depth of cut (RDOC) and higher axial depth of cut (ADOC). In traditional milling you can remove close to 50% of material radially, but the axial depth of cut and speed is reduced compared to HEM. This ultimately puts a lot of heat into a concentrated portion of the tool.

Tooling Using HEM vs Traditional Milling

Because the tool paths for high efficiency milling and traditional milling differ, you can use different tools to also gain efficiencies. HEM tool paths create favorable conditions for the endmill with light radial depths of cut. Therefore, you can use tools with smaller diameters and more flutes. A smaller diameter tool costs less than a larger diameter tool. The added flutes on an endmill create a stronger core on the tool. The stronger core adds more rigidity in your tool, allowing you to handle those greater axial depths of cuts with less deflection.

HEM vs Traditional Milling Technique

There are two key variables that reduce a tool’s life quickly – heat and vibration. HEM does a great job to reduce both factors. When you take light radial depths of cut, you create something called “chip thinning”. Once you take the radial depth of cut below 50%, your chip thickness decreases. Decreased chip thickness can lead to poor part finish and premature tool wear. You can combat this by changing (increasing) feed rate.

Heat: As the endmill engages into a cut, heat and friction will start to break down the coating and edge over time. Traditional milling techniques put pressure on a concentrated area of the tool’s flutes. HEM reduces pressure by moving along the workpiece quicker at higher feeds and dispersing the heat amongst more flutes.

Vibration: Vibration is reduced during HEM because the axial depth of cut comprises most, if not all, of the cutting edge. This engages several flutes at a time, keeping the load on the endmill stable.

Next Steps

Please be on the lookout for future articles with more “in-depth” techniques regarding high efficiency milling. In the meantime, please feel free to contact your local Butler Bros. sales representative for assistance on tooling and techniques for HEM. If you’d like to find out who your local representative is, please email your company name and location to and ask for the contact info of the local Butler Bros. representative in the area. Or please give us a call at 888-784-6875 and our staff will point you in the right direction.

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