Speeds and Feeds

In This Lesson

• Discuss different cutting tools

• Learn the definition of speeds and feeds

• Calculate cutting speeds and feed rates

• Practice

Basic Cutting Tools

Center Cutting End

Mill

Ball End Mill

Non-Center Cutting End

Mill

Indexable Shell Mill

Basic Cutting Tools

Combination

Drill & Countersink

Spotting Drill

Countersink

Flutes

2 Flute End Mill

• More room for chip evacuation

• Used for light metals

• Weak, short tool life

4 Flute End Mill•More cutting edges, longer tool life

•Used for harder metals

•Clogs easily in deep cuts

Center vs. Non-Center Cutting

2 Flute Center Cutting

4 Flute Center Cutting

4 Flute Non-Center

Cutting

Milling ToolsTool Description Application

¼” 2 Flute HSS Single End Mills

For Cutting Aluminum – 3/8

Shank x 1 ¼ cutting length

Facing, profiling, Pocketing, Slotting,

Roughing and Finishing

¼” 2 Flute Ball End Mill for

Aluminum – 3/8 shank x 1 ¾

cutting length

Surfacing, Slotting, profiling,

Roughing and Finishing

Milling ToolsTool Description Application

¼” Countersink & De-burring

Tool – 90 Degree

Engraving, De-burring,

countersink, Spot drilling

#3 Combined drill &

countersink 90 Degree

Spot drilling, Engraving

Milling ToolsTool Description Application

¼” spotting drill 90 deg

Spot drilling, Engraving

Cutting Tool Material Video

Definitions

• Cutter Speed – The rate of a tool measured in surface feet per minute.

• Spindle Speed – The number of revolutions per minute (RPM) that is made by the cutting tool of a machine.

• Feed – The distance advanced by the cutting tool along the length of the work for every revolution of the spindle.

Spindle Feeds Formula• Defined in revolutions per minute (RPM)• Found by dividing the cutter speed by the

circumference of the tool

N =CS (ft/min)

C (in.)

N =CS 12 (in./min)

d (in.)

circumference

Recommended Cutting SpeedsMilling Speeds for High Speed Steel Tools

Material Cutting Speed in surface ft/min

Magnesium 300

Aluminum 250

Brass and Bronze 150

Copper 100

Cast Iron (Soft) 80

Cast Iron (Hard) 50

Mild Steel 90

Cast Steel 80

Alloy Steel (Hard) 40

Tool Steel 50

Stainless Steel 60

Titanium 50

High Manganese Steel 30

Note: Double Speed for Carbide Cutting Tools

Example

What spindle speed should be used to mill aluminum with a ½ inch end mill?

Cutting Speed for Aluminum is 250 surface ft/min

CS 12 (in./min)

d (in.)N =

Example

What spindle speed should be used to mill aluminum with a ½ inch end mill?

Cutting speed for aluminum is 250 surface ft/min

250 ft/min 12

0.5 in.N = 1910 RPM=

CS 12 (in./min)

d (in.)N =

Your TurnWhat spindle speed should be used to mill soft cast iron with a ¼ inch end mill?

Cutting speed for soft cast iron is 80 surface ft/min

80 12

0.250N = = 1222 RPM

CS 12 (in./min)

d (in.)N =

Calculating Feed Rates

Fm = ft x nt x N

Fm = Feed rate in inches/min

ft = Feed in inches/tooth

nt = Number of teeth on the tool

N = Spindle speed = CS 12 (in./min)

d (in.)

Recommended Tool FeedTool Feed (in./tooth)

Material Face Mill Side Mill End Mill

Magnesium .005-.020 .004-.010 .005-.010

Aluminum .005-.020 .004-.010 .005-.010

Brass and Bronze .004-.020 .004-.010 .005-.010

Copper .004-.010 .004-.007 .004-.008

Cast Iron (Soft) .004-.016 .004-.009 .004-.008

Cast Iron (Hard) .004-.010 .002-.006 .002-.006

Mild Steel .004-.010 .002-.007 .002-.010

Alloy Steel (Hard) .004-.010 .002-.007 .002-.006

Tool Steel .004-.008 .002-.006 .002-.006

Stainless Steel .004-.008 .002-.006 .002-.006

Titanium .004-.008 .002-.006 .002-.006

High Manganese Steel .004-.008 .002-.006 .002-.006

Note: Double Speed for Carbide Cutting Tools

Example Feed RateCalculate the feed rate for end milling aluminum with a 2 flute, ½ inch HSS end mill.

Fm = ft nt N

ft=.005 in./tooth

Tool Feed (in./tooth)

Example Feed RateCalculate the feed rate for end milling aluminum with a 2 flute, ½ inch HSS end mill.

Ft = 0.005 in./tooth

nt= 2 teeth

= 1910 RPM250 12

0.5=

Fm = 0.005 2 1910Fm = 19 in./min

Fm = ft nt N

CS 12 (in./min)

d (in.)N =

Your TurnCalculate the feed rate for face milling aluminum with a 4 flute, ¾ inch HSS end mill.

Ft = 0.005 in./tooth nt= 4 teeth

N = = 1273 RPM250 12 0.75

=

Fm = 0.005 4 1273

Fm = 25.46 in./min

Fm = ft nt N

CS 12 (in./min)

d (in.)

Factors That Affect Feed Rates

• Power of spindle motor

• Condition of cutting tool

• Depth of cut

• Quality of surface finish required

• Roughing vs. finish cuts

• Condition of the machine

• Strength of fixture

Tool Feed Rate for Holes

Tool Feed Rate (ipm) = ipr RPM

Feed in inches/minute

Penetration rate in inches/revolution

Spindle speed in revolutions/minute

Recommended Drilling Feeds

Drilling Feeds

Drill Diameter (in.) Drill Feed Rate (ipr)

< ⅛ .001 – .002

⅛ – ¼ .002 – .004

¼ – ½ .004 – .007

½ – 1 .007 – .015

> 1 .015 – .025

Drill Feed Example

250 12 0.375

= 2,546 RPM

What tool feed rate should be used for drilling a .375 inch hole in aluminum?

Tool Feed Rate (ipm) = ipr RPM

CS 12 (in./min)

d (in.)N =

=

Drill FeedThe tool diameter is given in decimal form

Drilling Feeds

Drill Diameter (in.)

Drill Feed Rate (ipr)

< 0.125 .001 – .002

0.125. – 0.25 .002 – .004

0.25 – 0.5 .004 – .007

0.5 – 1 .007 – .015

> 1 .015 – .025

The diameter is .375.

Tool Feed Rate (ipm) = ipr RPM = 0.005 2546 = 12.73 ipm

Your Turn

What tool feed rate should be used for drilling a .25 inch hole in copper?

Tool Feed Rate (ipm) = ipr x rpm

100 12 0.25

= 1,528 RPM

CS 12 (in./min)

d (in.)N =

=

Drill FeedDrilling Feeds

Drill Diameter (in.)

Drill Feed Rate (ipr)

< 0.125 .001 – .002

0.125. – 0.25 .002 – .004

0.25 – 0.5 .004 – .007

0.5 – 1 .007 – .015

> 1 .015 – .025

Our diameter is 0.25

Tool Feed Rate (ipm) = ipr RPM = 0.004 1528 = 6.1 ipm

Special Operations

Other special operations require slower speeds:

Reaming – ½ to ⅔ of that used for drilling the material

Counterboring – ¼ of that used for drilling the material

Countersinking – ¼ of that used for drilling the material

Tapping (threading) – Determined by many factors (usually range from 50 to 300 RPM)

CS 12 (in./min)

d (in.)N =

References

Kibbe, R.R., Neely, J.E., Meyer, R.O., & White, W.T. (2002). Machine tool practices. Upper Saddle River, NJ: Prentice Hall.

Oberg, E., Jones F. D., Horton, H. L., & Ryffell, H. H. (2000). Machinery’s handbook (26th ed.). New York, NY: Industrial Press Inc.