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

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

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.

Basic Cutting Tools Combination Drill & Countersink Spotting Drill

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

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

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

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

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

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

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

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. Cutter 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. Different materials use different spindle speed rates. If the rate is too fast, the machine will wear out quickly. This can be expensive. If the rate is too slow, time is wasted. With some materials, the tool can actually bond to the material at slow speeds. This can also be costly. N = Spindle speed (rpm) CS = Cutting speed (surface ft / min) d = Diameter (in.) / rev Project Lead The Way, Inc. Copyright 2008

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

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

Your Turn What spindle speed should be used to mill Brass with a ¼ inch end mill? N = CS  12 in. d ft See teacher for solution

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 =

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 .005-.020 .004-.010 .005-.010 Aluminum Brass and Bronze .004-.020 Copper .004-.007 .004-.008 Cast Iron (Soft) .004-.016 .004-.009 Cast Iron (Hard) .002-.006 Mild Steel .002-.007 .002-.010 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

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=0.005 in. tooth ● rev Project Lead The Way, Inc. Copyright 2008

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=0.005 in. tooth  rev nt = 2 teeth fm = 0.005 in.  2 teeth  1,910 rpm tooth  rev fm = 19.1 in. min

Your Turn Calculate the feed rate for face milling aluminum with a 4 flute, ½ inch HSS end mill. See teacher for solution

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. Project Lead The Way, Inc. Copyright 2008

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

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 = 0.002 in.  4 teeth  687 rpm 2 nt = 4 teeth ft = 0.002 in. tooth  rev pfr = 2.7 in. min

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

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 .005-.020 .004-.010 .005-.010 Aluminum Brass and Bronze .004-.020 Copper .004-.007 .004-.008 Cast Iron (Soft) .004-.016 .004-.009 Cast Iron (Hard) .002-.006 Mild Steel .002-.007 .002-.010 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

Now Your Turn Calculate the plunge feed rate for plunging copper with a 4 flute, ¼ inch HSS end mill. See teacher for solution

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

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.