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Guide to Calculating Speed and Feed

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Anyone who is serious about CNC or milling needs to understand the importance of optimizing speed and feed. You need optimized speed and feed to get the best surface finish, as well as the best lifespan out of your tools. Calculating speed and feed correctly will also help you achieve the fastest machining time so you can increase your efficiency, and ultimately, your profits. Whether you’re working with a face milling cutter or computer numerical control machine, utilize this guide to help you get the right speed and feed calculations for your project.

Speed and Feed Calculations

If you’re looking for milling cutters for sale, you need to keep a few things in mind. In addition to choosing a milling cutter that has the capacity to meet your needs, you also need to make sure you calculate its speed and feed accurately. Accurate calculations deliver the best results.

Milling operations feed a workpiece into a cutting tool that rotates as it cuts (such as a face milling cutter). To determine the speed and feed rate for this type of operation, you’ll need to use calculations that include the number of teeth used to cut, the desired diameter of the tool, the cutting feed, and the cutting speed.

Here are some calculation formulas you can do yourself to figure out your speed and feed.

  • Speed (RPM) = (SFM x 3.82) / D

In the above calculation, “SFM” stands for “Surface Feet per Minute”, while “RPM” stands for “Revolutions Per Minute.” “D” refers to the diameter of the tool. The calculation for determining feed is as follows:

  • Feed (IPM) = RPM x FPT x Z

In this calculation, “IPM” refers to “Inches per Minute” while “FPT” stands for “Feed per Tooth.” Finally, Z refers to the number of teeth in the cutter.

In addition to these formulas, you may also want to familiarize yourself with the formulas for Adjusted Feed per Tooth – Chip Thinning (also known as AFPT), Inches per Tooth (also known as IPT) and Metal Removal Rate – Cubic Inches per Minute (MRR). Here are those formulas:

  • AFPT (at less than ½ diameter width of cut) = IPM x square root of (tool diameter / width of cut)
  • IPT = (inches per minute / revolutions per minute) / number of teeth in cutter
  • MRR = inches per minute * width of cut * depth of cut

These calculations can help you estimate different aspects of your project more accurately. Alternatively, you can download a speed and feed calculator that allows you to simply plug in the numbers and the calculator will do the rest for you. If you aren’t naturally good at making calculations or if you want to provide a new employee with an easy way to make these calculations in minimal time, an online calculator can become a very valuable tool.

Don’t underestimate the importance of this simple tool and its ability to help you streamline your milling operations and obtain the fastest operating time possible for your different projects. Using speed and feed calculators can help you keep your various projects on track and on time.