“Calculating Spindle Speed”

In machining, spindle speeds, also called “cutting speeds”, are extremely important for tool life, part finishes and over all part quality.  

This is especially true in CNC machining where the programmer must be able to calculate the spindle speed based on recommended “cutting speeds” usually given in either “Feet Per Minute” (FPM, U.S. Units) or in “Meters Per Minute” (MPM, Metric Units).

Below are instructions on how to calculate spindle speeds using cutting speeds.  I did not put the instructions in “Formula Form” but instead just in a Step by Step instructional form.  For most people (myself included) it is easier to follow.

Cutting Speed to RPM ( U.S. Units):

(1) Obtain Recommended Cutting Speed in FPM (Feet Per Minute)

(2) Multiply FPM (Cutting Speed in Feet Per Minute) by 12

(3) Multiply the Stock or Tool Diameter by pi (3.1416)

(4) Divide Step 2 by Step 3 to obtain the RPM


Example:

We want to calculate the RPM for a .750” cut diameter or .750” diameter tool with the recommended cutting speed of 300 FPM (Feet Per Minute)

300 FPM x 12 = 3600 (Ref. Step 2)

.750” Diameter x 3.1416 = 2.3562 (Ref. Step 3)

Divide 3600 by 2.3562 = 1528 RPM (Ref. Step 4)

Cutting Speed to RPM ( Metric Units):

(1) Obtain Recommended Cutting Speed in MPM (Meters Per Minute)

(2) Multiply MPM (Cutting Speed in Meters Per Minute) by 1000

(3) Multiply the Stock or Tool Diameter by pi (3.1416)

(4) Divide Step 2 by Step 3 to obtain the RPM


Example:

We want to calculate the RPM for a 22mm cut diameter or 22mm diameter tool with the recommended cutting speed of 125 MPM (Meters Per Minute)

125 MPM x 1000 = 125000 (Ref. Step 2)

22mm Diameter x 3.1416 = 69.1152 (Ref. Step 3)

Divide 125000 by 69.1152 = 1809 RPM (Ref. Step 4)

RPM to Cutting Speed ( U.S. Units):

(1) pi (3.1416) x Stock or Tool Diameter in Inches x RPM

(2) Divide Step 1 by 12 to obtain the Cutting Speed in FPM (Feet Per Minute)


Example:

We want to calculate the Cutting Speed for a .750” cut diameter or .750” diameter tool with a RPM of 5000

3.1416 x .750” x 5000 = 11781 (Ref. Step 1)

Divide 11781 by 12 = 982 FPM (Ref. Step 2)

RPM to Cutting Speed ( Metric Units):

(1) pi (3.1416) x Stock or Tool Diameter in Millimeters x RPM

(2) Divide Step 1 by 1000 to obtain the Cutting Speed in MPM (Meters Per Minute)


Example:

We want to calculate the Cutting Speed for a 25mm cut diameter or 25mm diameter tool with a RPM of 5000

3.1416 x 25mm x 5000 = 392700 (Ref. Step 1)

Divide 392700 by 1000 = 392.7 MPM (Ref. Step 2)

View My Stats

Now included in the Web Machinist Software Program is the “Spindle Speed and Feed Calculator” Shown Below:

Web Machinist Software Program:

Web Machinist Software

“Spindle Speed Conversion Calculator”  Convert SFM to RPM and RPM to SFM Quickly and Easily!

Spindle Speed Calculator Web Machinist Special Deal!

Advertisers:

Order Page

Click Here to Order the Web Machinist Software

Web Machinist 8.0 is Now Available! Only $59.00! TODAY ONLY! (Save 50% = $50 Savings)

Home / Order Web Machinist  Site Map  Software    Contact / Special Deal / Upgrade   /FAQ’s  Tutorials  Machining Formulas

50+ Machining Calculators are in the Program!

Only $59.00 Save $50.00 Click Here

Favorite Links:

WebMachinist.net SpurGearCalculator.com BluePlanetProducts.Net  TruePositionCalculator.Com MachinistCalculators.com PeckDrilling.com MachiningFormulas.com

Order Page

Click Here for More Info

Blue Planet Income Products 1.0.zip

Make money from Home!

Find Hundreds of Home Based Income Opportunities with this FREE Software!

Click Here to Download it Now