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Speed and Feed Calculator FAQ

How do you calculate speed and feed?

Speed (RPM) = (Surface Feet per Minute x 3.82) / Diameter of the Tool  

Feed Rate = RPM x Chip Load x Number of Teeth

RPM = Of the tool or workpiece

Chip Load = The amount of material removed, per revolution per cutting edge

Number of Teeth = The number of edges, facets, or flutes.

What RPM should you mill steel?

Multiple factors affect the spindle speed (RPM) when milling steel, these include:

The type of steel:

  • Overall hardness
  • Heat treatment
  • Alloying composition

The type of tooling:

  • Material (high-speed steel, carbide, etc.)
  • Shape
  • Condition (new vs worn)

The type of milling machine:

  • Use of coolant
  • Stability of work holding fixtures 

Most specialty steel manufacturers will make available machining information if it is not a common steel variant.  

How does a CNC mill calculate speeds and feeds or SFM?

A CNC mill calculates speeds and feeds or SFM based on the information the user enters. The type of CNC mill, the type of machine controller, and the age of the machine will affect the amount of information that can be input directly into the machine. Historically G-code was created externally from a CNC machine and then loaded onto the machine. Externally created G-code was authored either with a dedicated CAM software or with a plug-in embedded in the 3D parametric modeling software. The user would input the same CNC machine they want to create the part on (with the specific work holding fixture), the type of tooling (manufacture, part number etc.), and the specific material being machined. The software generates the speeds and feeds based on the part's geometry and all the inputted information. This creates the optimal speeds and feeds or SFM tailored to the exact part and CNC machine.    

How do you calculate feed for turning?

Turning Feed Rate = Rotational Speed (N) x Feed Rate (fr)

Rotational Speed (N) = Cutting Speed (SFM) / π x Original Diameter 

Feed Rate (fr) = Rotational Speed (N) x Feed (f). Note: Feed (f) is in distance/revolution.  

How do you calculate SFM in machining?

Milling Surface Feet per Minute = (RPM x Tool Diameter) / 3.82

Turning Surface Feet per Minute = 0.262 x Part Diameter x RPM

How does SFM calculate RPM?

Surface Feet per Minute = (RPM x Circumference) / 12  

Note: The circumference unit is in inches and is dependent on if it’s a milling or turning operation. For milling operations, the circumference is of the cutter (tool in the spindle). For turning operations, the circumference is of the workpiece (the material in the chuck).

What is Surface Feet Per Minute (SFM)?

Surface feet per minute (SFPM or SFM) is the combination of a physical quantity (surface speed) and an imperial and American customary unit (feet per minute or FPM). It is defined as the number of linear feet that a location on a rotating component travels in one minute.

What is Inches per minute (IPM)?

Inches per minute (IPM) is a speed measurement of how many inches traveled in a minute, without regard to direction. In machining, it is primarily used as a feed rate (imperial units).  

Determine the spindle speed for turning, milling, drilling, and reaming with these charts and cutting speed calculators.

Turning speeds are adjusted to the feed rate of the mini lathe (0.004/rev.), a depth of cut of 0.040, and a tool life of 180 minutes.

Material AISI/SAE/ASTM Designation HSS
Feet/Minute
Carbide
Feet/Minute
Free machining plain carbon steels (resulfurized) 1212, 1213, 1215 270 - 290 820 - 1045
Free machining plain carbon steels 1108, 1109, 1115, 1117, 1118, 1120, 1126, 1211 215 - 235 950
Free machining plain carbon steels 1132, 1137, 1139, 1140, 1144, 1146, 1151 70 - 215 670 - 800
Free machining plain carbon steels (Leaded) 11L17, 11L18, 12L13, 12L14 200 - 260 800 - 820
Plain carbon steels 1006, 1008, 1009, 1010, 1012, 1015, 1016, 1017, 1018, 1019, 1020, 1021, 1022, 1023, 1024, 1025, 1026, 1513, 1514 125 - 215 800 - 885
Plain carbon steels 1027, 1030, 1033, 1035, 1036, 1037, 1038, 1039, 1040, 1041, 1042, 1043, 1045, 1046, 1048, 1049, 1050, 1052, 1524, 1526, 1527, 1541 55 - 180 670 - 970
Free machining alloy steels (resulfurized): 4140, 4150 70 - 200 430 - 685
Water hardening tool steel W1, W2, W5 180 590
Cold work, oil hardening tool steel O1, O2, O6, O7 125 590
Cold work, air hardening tool steel A2, A3, A4, A6, A7, A8, A9, A10 80 - 125 355 - 365
Stainless steels (Austenitic) 201, 202, 301, 302, 304, 304L, 305, 308, 321, 347, 348 115 - 135 570
Cast Iron ASTM Class 20, 25, 30, 35, 40 145 - 215 410
Brass C35600, C37700, C36000, C33200, C34200, C35300, C48500, C34000 300 - 350 1170
Bronze C65500, C22600, C65100, C67500 200 - 250 715
Wrought aluminum 6061-T6, 5000, 6000, and 7000 series. 500 - 600 2820
Cast aluminum Sand and permanent mold casting alloys 600 - 750 2820
Material AISI/SAE/ASTM Designation Feet/Minute
Free machining plain carbon steels (resulfurized) 1212, 1213, 1215 130 - 140
Free machining plain carbon steels 1108, 1109, 1115, 1117, 1118, 1120, 1126, 1211 115 - 130
Free machining plain carbon steels 1132, 1137, 1139, 1140, 1144, 1146, 1151 35 - 70
Free machining plain carbon steels (Leaded) 11L17, 11L18, 12L13, 12L14 110 - 140
Plain carbon steels 1006, 1008, 1009, 1010, 1012, 1015, 1016, 1017, 1018, 1019, 1020, 1021, 1022, 1023, 1024, 1025, 1026, 1513, 1514 65 - 110
Plain carbon steels 1027, 1030, 1033, 1035, 1036, 1037, 1038, 1039, 1040, 1041, 1042, 1043, 1045, 1046, 1048, 1049, 1050, 1052, 1524, 1526, 1527, 1541 25 - 100
Free machining alloy steels (resulfurized) 4140, 4150 35 - 100
Water hardening tool steel W1, W2, W5 85
Cold work, oil hardening tool steel O1, O2, O6, O7 50
Cold work, air hardening tool steel A2, A3, A4, A6, A7, A8, A9, A10 40 - 50
Stainless steels (Austenitic) 201, 202, 301, 302, 304, 304L, 305, 308, 321, 347, 348 70 - 75
Cast Iron ASTM Class 20, 25, 30, 35, 40 70 - 100
Brass C33200, C34000, C34200, C35300, C35600, C36000, C37700,   C48500 100 - 200
Bronze C22600, C65100, C65500, C67500 30 - 80
Wrought aluminum 6061-T6, 5000, 6000, and 7000 series. 165
Cast aluminum Sand and permanent mold casting alloys 165
Material AISI/SAE/ASTM Designation Drilling Feet/Minute Reaming Feet/Minute
Free machining plain carbon steels (resulfurized) 1212, 1213, 1215 120 - 125 80
Free machining plain carbon steels 1108, 1109, 1115, 1117, 1118, 1120, 1126, 1211 100 - 120 75 - 80
Free machining plain carbon steels 1132, 1137, 1139, 1140, 1144, 1146, 1151 35 - 70 20 - 45
Free machining plain carbon steels (Leaded) 11L17, 11L18, 12L13, 12L14 90 - 130 60 - 85
Plain carbon steels 1006, 1008, 1009, 1010, 1012, 1015, 1016, 1017, 1018, 1019, 1020, 1021, 1022, 1023, 1024, 1025, 1026, 1513, 1514 60 - 100 40 - 65
Plain carbon steels 1027, 1030, 1033, 1035, 1036, 1037, 1038, 1039, 1040, 1041, 1042, 1043, 1045, 1046, 1048, 1049, 1050, 1052, 1524, 1526, 1527, 1541 25 - 90 15 - 60
Free machining alloy steels (resulfurized) 4140, 4150 30 - 90 15 - 60
Water hardening tool steel W1, W2, W5 85 55
Cold work, oil hardening tool steel O1, O2, O6, O7 45 30
Cold work, air hardening tool steel A2, A3, A4, A6, A7, A8, A9, A10 30 - 50 20 - 35
Stainless steels (Austenitic) 201, 202, 301, 302, 304, 304L, 305, 308, 321, 347, 348 50 - 55 30 - 35
Cast Iron ASTM Class 20, 25, 30, 35, 40 80 - 100 50 - 65
Brass C35600, C37700, C36000, C33200, C34200, C35300, C48500, C34000 160 - 175 160 - 175
Bronze C65500, C22600, C65100, C67500 120 - 140 110 - 120
Wrought aluminum 6061-T6, 5000, 6000, and 7000 series. 350 - 400 350 - 400
Cast aluminum Sand and permanent mold casting alloys 350 - 400 350 - 400

What is feed per minute?

It is expressed in units of distance along the workpiece surface per unit of time, typically surface feet per minute (sfm) or meters per minute(m/min). Feed rate (IPR) IPR - Also called, feedrate, or called simply feed) is the relative velocity at which the cutter is advanced along the workpiece.

What is feed rate speed?

What is Feed Rate? Feed rate is the distance which the cutting tool during one spindle revolution. It is also defined as the velocity at which the cutter is advanced against the workpiece. It is measured in either inch per revolution or millimeters per revolution (ipr or mpr) for turning and boring processes.

What is feed rate formula?

The equation for the feed rate is: f = N C L n t \small f = N C_L n_t f=NCLnt. where: f f. f – Feed rate in inches per minute (IPM);

What is meant by feed rate?

Feed rate is the velocity at which the cutter is fed, that is, advanced against the workpiece. It is expressed in units of distance per revolution for turning and boring (typically inches per revolution [ipr] or millimeters per revolution).