Speeds and Feeds Calculator

Created by Luis Fernando
Based on research by
Christopher J. Q. McCauley Machinery’s Handbook, 26th Edition, Chapter: Machining Operations (2000)
Last updated: Aug 06, 2022

With this tool, you'll be able to calculate the speed and feeds or reamers, drill bits, millers, or any other machine tool.

Calculating the feed rate will give an idea of the time it will take to perform our machining work. On the other hand, the rotational speed calculation of drills or other machine tools will help us determine the spindle speed and predict the amount of electrical power needed. For that reason, we created this speeds and feeds calculator.

Keep reading to learn more about the different machine tool operations and the speed and feed rate formulas.

Different machine tool operations

One of the machine operations this calculator supports is turning, in which, intending to diminish its diameter, a circular piece (the workpiece) rotates while in contact with a stationary cutting tool.

Turning
Turning. Attribution: Florian Schott, CC BY-SA 4.0, via Wikimedia Commons

Within the hole-making operations of this calculator, we can find:

  • Drilling: making a circular hole in the workpiece using a drill bit as the tool.
Titanium drilling
Titanium drilling. Attribution: Cosme2c, CC BY-SA 3.0, via Wikimedia Commons
  • Reaming: slightly enlarging the size of an existing hole using a reamer (a multi-point cutting tool). In this operation, the objective is usually increasing the hole precision or quality.
  • Boring: similar to reaming, but usually with more significant diameter changes and less precision. The cutting tool is a boring bar that contains a single-point cutting tool.
  • Counterboring: enlarges the top part of an existing hole by creating a coaxial, flat-bottomed, cylindrical hole.
Counterbore hole
Counterbore hole. Attribution: Dvortygirl, CC BY-SA 3.0, via Wikimedia Commons

Finally, this calculator supports the following milling operations:

  • Face milling: creating a smoother finish of a flat surface of the workpiece.
  • End milling: making an extended cavity in the workpiece, such as a slot or complex surface contour, using an end mill.
  • Slab/side milling: creating large, broad surfaces that are parallel to the tool axis of rotation.

Rotation speed formula

One of the parts, the tool or the workpiece, will rotate in machining. For example, in drilling, the rotating part is the drill bit, while in turning, the rotating part is the workpiece.

When using imperial units, the formula to calculate the required rotating speed is:

RPM=12× Surface speed (ft/min)π×Diameter (in)\text{RPM} = \frac{12 \times\ \text{Surface speed (ft/min)}}{\pi \times \text{Diameter (in)}}

where:

  • RPM\text{RPM} is the velocity of the rotating part in revolutions per minute (rpm);
  • Surface speed (ft/min)\text{Surface speed (ft/min)} is the speed at which the tool travels relative to the workpiece (or vice-versa), in feet per minute (ft/min); and
  • Diameter (in)\text{Diameter (in)} is the diameter of the rotating part, in inches (in). For example, if we want to calculate the speed of a drill, the diameter to choose will be the drill bit diameter, but if we want to calculate the speeds and feeds of a turning process, the diameter to choose will be the workpiece diameter.

If using the metric system, the formula for the velocity of the rotating part (in rpm) is similar:

RPM=60× 1000 ×Surface speed (m/s)π×Diameter (mm)\text{RPM} = \frac{60 \times\ 1000\ \times\text{Surface speed (m/s)}}{\pi \times \text{Diameter (mm)}}

where:

  • Surface speed (m/s)\text{Surface speed (m/s)} — Speed at which the tool travels relative to the workpiece (or vice-versa), in meters per second (m/s); and
  • Diameter (mm)\text{Diameter (mm)} — Diameter of the rotating part, in millimeters (mm).

The surface speed, also known as cutting speed, depends on the machine tool operation, the tool material, and the workpiece material. The surface speed is not a fixed number but a range of recommended values, going from a minimum to a maximum recommended speed. The possibilities are enormous as there are usually two tool materials, eight operations, and a considerable amount of workpiece materials. Fortunately, our calculator will determine the value of the recommended surface speed for you when you specify the operation and materials.

🙋 The surface speed and chip load values this calculator uses come from Machinery's Handbook, 26th Edition, Chapter: Machining Operations.

Feed rate formula

Once we know the RPM, we can use the formula for feed rate calculation:

Feed rate = RPM × Chip load × # of teeth

where:

  • RPM — rotation speed of the rotating element, in revolutions per minute (rpm);
  • # of teeth — number of teeth of the curing tool; and
  • Chip load — the size of the workpiece each tooth removes, in inches or millimeters per tooth (in/tooth or mm/tooth)

If the chip load is in in/tooth, the resulting feed rate is in in/min, and if the chip load is in mm/tooth, the resulting feed rate is in mm/min.

How do I use this speeds and feeds calculator?

This calculator has two modes, and both use the formulas presented in the previous section to calculate the rotational speed and feed rate, but there are some differences:

  • Preset mode: the calculator will find the recommended surface speed and chip loads for you, as long as you specify the type of operation, tool material, workpiece material, and the number of teeth.
  • Custom mode: you'll be able to specify your custom surface speed and chip load.

If you have gotten this far, thanks for reading. Hopefully, now you have a better idea of how to calculate drill speeds, the speeds and feeds of reamers, and many more.

Luis Fernando
Calculator mode
Preset mode
Machine tool operation
Drilling
Materials and geometry
Tool material
High-speed steel (HSS)
Workpiece material
Aluminum
Tool/workpiece diameter
in
Speeds
Min rotation speed
rpm
Avg rotation speed
rpm
Max rotation speed
rpm
Feeds
Number of teeth
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