1. Speeds and Feeds Computer Integrated Manufacturing
© 2013 Project Lead The Way, Inc.

2. In This Lesson Identify common cutting tools
Learn the definition of speeds and feeds
Calculate cutting speeds and feed rate

3. Basic Cutting Tools Non-Center Cutting End Mill Ball End Mill
Indexable Shell Mill
Many different cutters are used during the milling process. The same cutting speed formula is used for each tool. Formula is presented on a subsequent slide.

4. Basic Cutting Tools Combination Drill & Countersink Spotting Drill

5. Flutes 4 Flute End Mill 2 Flute End Mill
More cutting edges, longer tool life
Used for harder metals
Clogs easily in deep cuts
More room for chip evacuation
Used for light metals
Weak, short tool life

6. Center Vs. Non-Center Cutting
4 Flute Non-Center Cutting
2 Flute Center Cutting
4 Flute Center Cutting

7. Milling Tools Tool 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

8. Milling Tools Tool Description Application
¼” Countersink & De-burring tool – 90 Degree
Engraving, de-burring, countersink, spot drilling
#3 Combined drill & countersink 90 degree
Spot drilling, engraving

9. Milling Tools Tool Description Application ¼” Spotting drill 90 deg
Spot drilling, engraving

10. Cutting Tool Material Video
Speeds and Feeds
Cutting Tool Material Video
CIM
Product Development
Play video: Cutting Tool Material and Cutting Tool Geometry
Project Lead The Way, Inc.
Copyright 2008

11. Speeds and Feeds
Definitions
CIM
Product Development
Cutting 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
Cutter speed must be converted to inches per minute so that it can be expressed as rpm. This gives us the spindle speed.
Feed (or chipload) must be converted to inches per minute to give us the feed rate.
Project Lead The Way, Inc.
Copyright 2008

12. Spindle Feeds Formula Defined in revolutions per minute (rpm)
Speeds and Feeds
Spindle Feeds Formula
CIM
Product Development
Defined in revolutions per minute (rpm)
Found by dividing the cutting speed by the circumference of the tool CS C
N =
C = circumference
N =
CS  12 in. d ft
CS, the cutting speed, is obtained from a machinery handbook.
A revolution is one complete rotation. This distance is called the circumference. The circumference of a circle is found by the formula d, where  is the constant value of approximately 3.14 and d is the diameter of the circle. In our formula, the diameter used is that of the tool being implemented.
Cutting speed is defined in feet per minute while circumference is defined in inches.
To convert so that the units match, we multiply feet by 12 since there are 12 inches in a foot.
Spindle speed is determined based on the materials to be cut. If the spindle speed is too fast, the tooling will wear out quickly which can be expensive. If the spindle speed is too slow then time is wasted. The cutting tool can actually bond to the material at slow speeds which can damage equipment and be costly.
N = Spindle speed (rpm)
CS = Cutting speed (surface ft / min)
d = Diameter (in.) / rev
Project Lead The Way, Inc.
Copyright 2008

13. Recommended Cutting Speeds
Speeds and Feeds
Recommended Cutting Speeds
CIM
Product Development
Milling 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
Alloy Steel (Hard) 40
Tool Steel
Stainless Steel 60
Titanium
High Manganese Steel 30
Note: Double Speed for Carbide Cutting Tools
Notice how the speeds are slower as you look down the chart. Why? The materials are harder as you move down the chart.
Project Lead The Way, Inc.
Copyright 2008

14. Speeds and Feeds
Example
CIM
Product Development
What spindle speed should be used to mill aluminum with a ½ inch end mill?
N =
CS  12 in. d ft
Start with the formula and substitute the known values. Note that the spindle speed was rounded down instead of following the traditional mathematical rules for rounding an answer. Rounding down results in a more conservative spindle speed.
N =
= 1,910 rpm
250 ft  12 in.
  0.5 in. ft
min
rev
Cutting Speed for Aluminum is 250 surface ft/min
Project Lead The Way, Inc.
Copyright 2008

15. Your Turn
What spindle speed should be used to mill Brass with a ¼ inch end mill?
N =
CS  12 in. d ft
Cutting speed for soft cast iron is 150 surface ft/min
150 ft  12 in.
  0.25 in. ft
min
rev
N =
= 2,293 rpm

16. Calculating Feed Rates
fm = ft x nt x N
fm = Feed rate in.
min
ft = Feed in.
tooth  rev
nt = Number of teeth on the tool
CS  12 in. d ft
N = Spindle speed =

17. Tool Feed (in./tooth*rev)
Speeds and Feeds
Recommended Tool Feed
CIM
Product Development
Tool Feed (in./tooth*rev)
Material
Face Mill
Side Mill
End Mill
Magnesium
Aluminum
Brass and Bronze
Copper
Cast Iron (Soft)
Cast Iron (Hard)
Mild Steel
Alloy Steel (Hard)
Tool Steel
Stainless Steel
Titanium
High Manganese Steel
Note: Double Speed for Carbide Cutting Tools
Notice that there are three feeds for each material, depending on whether it is a face mill, a side mill, or an end mill. Also, each material has a range of values attached to it. Typically you will use the smallest value to be cautious.
Project Lead The Way, Inc.
Copyright 2008

18. Example Feed Rate fm = ft  nt  N
Speeds and Feeds
CIM
Product Development
Example Feed Rate
Calculate the feed rate for end milling aluminum with a 2 flute, ½ inch HSS end mill.
fm = ft  nt  N
Tool Feed (in./tooth*rev)
HSS stands for high speed steel. What is the tool feed for aluminum?
ft= in.
tooth ● rev
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Copyright 2008

19. Example Feed Rate
Calculate the feed rate for end milling aluminum with a 2 flute, ½ inch HSS end mill.
N =
CS  12 in. d ft
250 ft  12 in.
  0.5 in. ft
min
rev
= 1,910 rpm =
fm = ft  nt  N
ft= in.
tooth  rev
nt = 2 teeth
fm = in  2 teeth  1,910 rpm
tooth  rev
fm = in.
min

20. Your Turn
Calculate the feed rate for face milling aluminum with a 4 flute, ½ inch HSS end mill.
N =
CS  12 in. d ft
250 ft  12 in.
  0.5 in. ft
min
rev
= 1,911 rpm =
fm = ft  nt  N
1,911 has been rounded. It is actually customary to wait until the last step to round.
ft= in.
tooth  rev
nt = 4 teeth
fm = in  4 teeth  1,911 rpm
tooth  rev
fm = in.
min

21. Factors That Affect Feed Rates
Speeds and Feeds
Factors That Affect Feed Rates
CIM
Product Development
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
We can mathematically calculate the feed rates, but other factors affect the speed rate as well. If your tool is dull, for example, it will cut slower.
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Copyright 2008

22. Plunge Feed Rate pfr = fm pfr = ft  nt  N fm = ft  nt  N 2 2
Speeds and Feeds
Plunge Feed Rate
CIM
Product Development
Feed rate at which mill can plunge into material
pfr = fm
fm = ft  nt  N
pfr = ft  nt  N 2 2
pfr = Plunge feed rate in.
min
fm = Feed rate in.
min
Project Lead The Way, Inc.
Copyright 2008

23. Example Plunge Feed Rate
Calculate the plunge feed rate for plunging into mild steel with a 4 flute, ½ inch HSS end mill.
Reference charts on next slides
N =
CS  12 in. d ft
90 ft  12 in.
  0.5 in. ft
min
rev =
= 687 rpm
fm = ft  nt  N
pfr = fm
pfr = ft  nt  N 2 2
688 has been rounded. It is actually customary to wait until the last step to round.
tooth  rev
pfr = in  4 teeth  687 rpm 2
nt = 4 teeth
ft = in.
tooth  rev
pfr = 2.7 in.
min

24. Recommended Cutting Speeds
Speeds and Feeds
Recommended Cutting Speeds
CIM
Product Development
Milling 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
Alloy Steel (Hard) 40
Tool Steel
Stainless Steel 60
Titanium
High Manganese Steel 30
Note: Double Speed for Carbide Cutting Tools
Project Lead The Way, Inc.
Copyright 2008

25. Tool Feed (in./tooth*rev)
Speeds and Feeds
Recommended Tool Feed
CIM
Product Development
Tool Feed (in./tooth*rev)
Material
Face Mill
Side Mill
End Mill
Magnesium
Aluminum
Brass and Bronze
Copper
Cast Iron (Soft)
Cast Iron (Hard)
Mild Steel
Alloy Steel (Hard)
Tool Steel
Stainless Steel
Titanium
High Manganese Steel
Note: Double Speed for Carbide Cutting Tools
Project Lead The Way, Inc.
Copyright 2008

26. Now Your Turn fm = ft  nt  N pfr = fm pfr = ft  nt  N 2 2
Calculate the plunge feed rate for plunging copper with a 4 flute, ¼ inch HSS end mill.
N =
CS  12 in. d ft
100 ft  12 in.
  0.25 in. ft
min
rev
= 1,529 rpm =
fm = ft  nt  N
pfr = fm
pfr = ft  nt  N 2 2
509 has been rounded. It is actually customary to wait until the last step to round.
tooth  rev
pfr = in  4 teeth  1,529 rpm 2
nt = 4 teeth
pfr = 24.5 in.
ft = in.
tooth  rev
min

27. Special Operations CS  12 in./ft N = d
Speeds and Feeds
Special Operations
CIM
Product Development
CS  12 in./ft d
N =
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)
There are some circumstances that require speeds slower than the one obtained from the formula.
In tapping, there is no special formula.
Project Lead The Way, Inc.
Copyright 2008

28. References Black, J., Kohser R. (2008). DeGarmo’s materials and
processes in manufacturing (10th ed.). Danvers, MA: John Wiley & Sons, Inc.
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.