When machining materials like 304 stainless steel, optimizing cutting parameters is crucial for achieving efficiency and tool longevity. Tormach Product Manager Tom Zelickman took us behind the scenes of his testing process, demonstrating real-world cutting strategies for 304 stainless on the Tormach 1500MX CNC mill. By sharing his methods and adjustments, Tom provides machinists with a solid starting point for dialing in their own machining parameters.
Understanding the Testing Approach
The goal of this testing series is to provide transparency into how cutting parameters are determined and adjusted for different materials. The process begins with industry-standard speeds and feeds for a given material, followed by real-time adjustments based on spindle load, cutting forces, and overall machine behavior.
To ensure accuracy, all tests were performed using off-the-shelf tooling available from Tormach. This means users can replicate these results without needing specialized or high-end tools. The 1500MX, with its epoxy granite frame and high-performance capabilities, provided a stable platform for testing aggressive cutting parameters.
Facing Operations and Spindle Load Management
The first test focused on a facing operation using a 1.5-inch, four-flute YG face mill (part number 53084). Tom started with an initial depth of cut at 0.1 inches and width of cut of 0.5 inches which kept the spindle load around 70 to 100 percent for a balance between efficiency and continuous operation.
Observing the results, he noted that if he needed a better surface finish, he would add a finishing pass; he would have taken a lighter cut of 0.09 inches, leaving 0.01 inches for a final cleanup. This approach would improve the surface finish while reducing cutting forces.
Adaptive Toolpaths and Fine-Tuning Feed Rates
Next, Tom tested an adaptive roughing toolpath using a 5/16-inch four-flute carbide end mill from the Tormach High-Performance Tooling Kit for Steels. The initial default settings from the ToolPath PreTool application ran at an industry standard of 200 surface feet per minute (SFM) and a chip load of 0.00125 inches per tooth (IPT).
However, this setup resulted in a low spindle load of around 35 to 40 percent, indicating the 1500MX could push the cut harder. To optimize material removal, Tom increased the feed rate to 200 percent (0.0025 IPT), raising the spindle load without overloading the tool.
Despite some initial harmonics in one cutting direction, Tom further optimized by increasing the cutting speed to 300 SFM and a chip load of 0.004 IPT per tooth. This adjustment eliminated chatter and improved surface finish while bringing the spindle load to a more efficient 80 to 100 percent range.
Deep Cuts and High Spindle Loads
Tom then tested a deeper three-quarter-inch depth of cut, reducing the feed rate slightly to maintain cutting stability. This deeper cut increased spindle load to 110 to 115 percent, demonstrating the 1500MX’s ability to handle aggressive material removal.
Throughout testing, Tom monitored toolpath efficiency and spindle response, making real-time adjustments to feed rates and depths of cut. His final optimized toolpath achieved significantly higher material removal rates than industry-standard recommendations, without sacrificing tool life or surface quality.
Key Takeaways from 304 Stainless Testing
— Industry standards for 304 stainless suggest 200 SFM. and .0012 IPT chip load.
— Optimized cutting speeds reached 300 SFM and .004 IPT, significantly improving
material removal rates.
— Spindle load monitoring: Load meters help you make adjustments and get the most from your machine.
— Deeper cuts can be handled effectively but may require minor adjustments.
— Adaptive toolpaths are an effective way to optimize material removal rates when roughing in load ranges for which
the machine is designed.
Tom’s testing on the 1500MX highlights the importance of adjusting parameters beyond generic recommendations. By monitoring spindle load, adjusting feed rates, and fine-tuning cutting speeds, machinists can optimize their operations for better efficiency and tool life.
