Feeds and Speeds Calculator
When setting up a CNC milling operation, the two parameters that need to be determined are the spindle speed, N, and the table feed rate, f_r (see the figure below). The main factors that drive the final spindle speed and the table feed rate are the desired cutting speed, V, and the desired feed per tooth, f_t. The cutting speed is the relative velocity between the cutting teeth and the material and the feed per tooth is the chip thickness. The recommended cutting speed depends on the material being machined and the cutting tool material. The table below gives typical values when using a high-speed steel cutter (table source: https://en.wikipedia.org/wiki/Speeds_and_feeds).
The desired feed per tooth is generally not as material dependent and general guidelines are to use 0.005 in for roughing operations and 0.002 in for finishing operations.
The cutting tool geometry also impacts the required table feed rate and spindle speed. Specifically, the cutter diameter, D, and the number of teeth on the cutter, n_t. The smaller the cutter diameter, the higher the required spindle speeds will be to maintain the desired cutting speeds, this is why the small diameter cutting tools use in dentistry required spindle speeds in excess of 100,000 rpm. An increase in the number cutting teeth allows for a higher table feed rate to be used while maintaining the same feed per tooth. The main benefit of an increased number of teeth is an increased material removal rate, resulting in shorter overall machine times.
Inputs
First, define the desired cutting speed and the feed per tooth (metric units can be used as will by changing the units in the input fields):
Outputs
The required spindle speed and table feed rate to sustain the above cutting parameters are provided below. Note that the rpm unit is represented in EngineeringPaper.xyz as [cycles/min]. The table feed rate can also be output in [mm/sec] by changing the [in/min] value in the right hand side of the table feed rate query statement to [mm/sec].
=1527.8874536822 (cycles)/(min)
=12.2230996294576 (in)/(min)
