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Home >>Basic Machining Math >>General Speeds and Feeds Formulas

General Speeds and Feeds Formulas

December 24, 2010, 2:10 pm

Article Summary

Eldar Gerfanov

December 24, 2010, 2:10 pm

Eldar Gerfanov

September 30, 2019, 1:11 am

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by Eldar Gerfanov

Author Summary

Fri December 4, 2020, 1:28 pm

Fri December 4, 2020, 1:28 pm

Free Online Speed and Feed Calculators

Code

Imperial Speed and Feed Calculator

RPM= 12 x SFM = Please enter Speed and Diameter
3.14 x in

Feed Rate = RPM x x in = Please enter RPM, number of teeth and chip load (in/min)

Code

Metric Speed and Feed Calculator

RPM= 1000 x M/min = Please enter Speed and Diameter
3.14 x mm

Feed Rate = RPM x x mm = Please enter RPM, number of teeth and chip load (mm/min)

Want something better?

Try our desktop  HSMAdvisor Speed and Feed Calc or Mobile/Online FSWizard

More about formulas needed to calculate turning, drilling and of course milling speeds and feeds

Here are few basic formulas with term explanations to get you going: 

Calculating Spindle Speed (RPM) Using Imperial Cutting Speed:

Code

RPM= 12 x SFM
3.14 x Diameter

Simplified imperial formula:

RPM= 3.8 x SFM
Diameter

Calculating Spindle Speed (RPM) using Metric Cutting Speed:

Code

RPM= 1000 x SMM
3.14 x Diameter

Simplified metric formula:

RPM= 318 x SMM
Diameter


Calculating Feed Rate :

Feed_Rate=RPM x N(teeth) x CL(chip load)

Definitions

  • RPM = Revolutions Per Minute, Spindle Speed, Number of revolutions of spindle per minute
  • SFM = Imperial. Surface Feet Per minute, Cutting speed, Speed at which tip of tool travels through material
  • SMM= Metric. Surface Meters Per minute, Cutting speed, Speed at which tip of tool travels through material
  • Feed_Rate = Inches Per Minute or Millimeters Per Minute, Feed Rate, Distance in inches or millimeters the tool the will travel through work piece per minute.
  • N = Number of teeth on the cutter
  • CL= Chip Load per tooth, This is the advancement of the cutter per revolution per each cutting edge. Otherwise generally explained as thickness of material each tooth takes per each revolution

Examples:

Calculate Speeds and Feeds for 1/2" (0.5 inch) 2 flute end mill in Mild Steel at cutting speed = 100(ft/min), Chip Load=0.001(inch per tooth)

Calculating Spindle Speed (RPM):

Code

RPM= 12 x SFM
3.14 x Diameter

=

RPM= 12 x 100(ft/min) =764(revs/min-1)
3.14 x 0.5(in)

For turning applications we do not need this formula since Spindle Speed is usually given in Constant Surface Speed (CSS), which uses SFM value directly. But if you still want to use RPM formula, then diameter value is the actual diameter of work piece.

Calculating Feed Rate in Inches Per Minute (IPM)

Formula used for milling and drilling applications. Please note that some tool manufacturers provide their recommended feed rate as feed per revolution. In such case do not multiply by number of teeth.

Code

Feed Rate = RPM x N x CL

Feed Rate = 800(RPM) x 2(teeth) x  0.001("chip load) =1.600 (in/min)

Easily Calculating Speeds and Feeds on your smartphone or computer

Our own free Speed and Feed Calculator can help you calculate cutting parameters for many different material groups. 

FSWizard Speed and Feed Calculator

General Speeds and Feeds Formulas
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