Examples Feeds and Speeds

Example #1

Using a 1/2" 3 Flute Endmill to cut Aluminum at half the diameter depth of cut with full width , what should my feeds and speeds be.

Step #1 – Determine the SFM -

With the Feeds and Speeds Chart you can determine that the cutting speed of aluminum (SFM) is 800-2000 SFM. Lets use 800 SFM for our example.

Step #2 – Determine the Feed per tooth -

With the same chart on the same row as the aluminum you can see the different feeds for the different sizes of cutter. Under the 1/2" column we have 0.004"

Step #3 – Calculator time -

So now you know the speed is 800 SFM and the feed per tooth should be 0.004” . Using the online calculator below enter in these numbers along with the tool information to get you the IPM feed of 73.

If you are a math wizard and what to know how to calculate this out without using the Online Calculator
I will explain. First you need to convert the 800 SFM into inch. Since there is 12 inches in a foot you get 9600 inches. Next you need to calculate the circumference of the ½ cutter. .500 x π = 1.571” . Now you can calculate the speed. 9600/1.571 = 6110 RPM . Since there is 3 flutes on this cutter you take the feed per tooth x 3 = 0.012 . For one revolution the cutter will cut 0.012 . 6110 RPM x 0.012” = 73.3 Inch per minute.


I calculated that I need 10,000 RPM for a 3/8” Endmill , but my machine has a max 3,000 RPM

Not all machines are capable of this high of rpm. If you have a max rpm of 3000 RPM then you should reduce your feed to the same feed per tooth at a lower speed.

What happens when I have too fast of a cutting speed.

Too fast of a cutting speed will cause more heat to build up and dull the cutter quicker.

How much of a cut should I take at one time?

Generally you do not want to cut anymore than half the diameter depth at full width of cut. Taking anymore than this can cause too much pressure on the cutter and not enough space for the cut material to exit the cutter.

Plunge vs Side cutting what is better?

Using the side of the endmill is more efficient and can handle much more material than the bottom of the endmill. When plugging solid I recommend 1/4 of the feed of side cutting.

How to stop a cutter from vibrating

The cutter will vibrate when the speed is too fast. Quick solution is to lower the RPM while maintaining or increasing the feed. This will cause more pressure on the cutter reducing the chance for vibration. Vibration can also be reduced with less tool stickout. Always hold the cutter as close to the end of the flutes when possible.