Speeds and Feeds

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Speeds and Feeds
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Spindle speeds given in RPM

• Revolutions Per Minute

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RPM Formula
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Applies to lathe, mills, drilling, etc.
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Cutting Speed

• normally given in tables
• based on Surface Feet Per Minute (SFPM)
• tool to work piece relationship
• of feet per minute that pass
• formula converts to inches per minute

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Cutting speed tables in text
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CS D ?

• Drill Press Dia of twist drill
• Lathe (Drilling) Dia of twist drill
• Lathe (Turning) Dia of work piece
• Vertical Mill Dia of cutter
• Horizontal Mill Dia of cutter

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Cutting speed constants influenced by

• tool material
• work material
• rigidity of setup
• use of cutting fluids

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Use lower cutting speeds

• for machining hard or tough materials
• if vibration or chatter

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Feed

• the machine movement that causes the tool to cut
  along the surface of the work
• usually measured in thousandths of an inch
• expressed in different ways on different machines

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Drilling Feed Rates

• feed expressed in inches per revolution (IPR)
• drill advances into the work a given amount for
  each revolution
• no formula - simply look up in table

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Sensitive drill press

• no power feed
• operator senses or feels the correct amount of
  feed

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Drilling feed variables

• drill diameter
• drill material
• work material

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Lathe Feed Rates (Two)
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1.) Turning

• expressed in IPR
• single point cutting tool advanced along the work
  a given amount for each revolution
• no formula - look up in table

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2.) Facing Feed Rates

• expressed in IPR
• no formula - look up in table
• problem of uniform finish on large diameter work
  piece
• CNC lathes equipped with Constant Surface Speed

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Turning Facing variables

• tool material
• work material
• surface finish required
• depth of cut - roughing cuts should be as much as
  possible without undo stress

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Milling

• Vertical and Horizontal Milling
• expressed in Inches Per Minute (IPM)

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Milling Feed Formula Feed (IPM) RPM x teeth
x IPT

• IPT inches per tooth taken from table
• Vertical Milling IPT usually between .001 and
  .010

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General rule for depth of cut in steel for end
mills

• standard end mill depth is approx. 1/2 diameter
  of the tool
• roughing end mill depth is approximately 1-1/2
  times the diameter of the tool

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Calculating drill point angle distance

• .3 x Diameter of the drill
• example 1/2 drill
• .5 x .3 .150 drill point angle distance