High speed spindles

Speeds and Feeds
Feed and Speed rates need to be determined to optimize machining time, surface finish, and tool life. Speeds and Feeds along with required horsepower can be calculated using the machinist’s handbook and a series of formulas. Information in the Machinists Handbook assumes production speeds: i.e. an average tool life of less than two hours. Production speeds state the maximum production for the cost of tooling, though they are sometimes impractical for the small jobs done at the machine shop. However, calculated speed and feed rates do give a useful reference in determining what rates should be used for our purposes. The following demonstrates how to calculate Speeds and Feeds for a surface milling or slotting operation.

Handbook Values:
  • SFM (ft/min) : (Surface Feet per Minute)- Also called Cutter speed. Speed of a point
    on the outside diameter of the tool. Value depends on material.
  • FPT (in) : (Feed Per Tooth)- Also called Chip Load. Amount of stock removed by
    each tooth during a single revolution. Value depends on stock material, tool size,
    and tool material.
  • HPF (HP*min/in3) : (Horse Power Factor) - number used to calculate power
    requirement. Value depends on material.

Other Variables:
  • D (in) : Diameter of tool
  • N : Number of teeth or flutes
  • DOC (in) : (Depth Of Cut)
  • RPM : (Rotations Per Minute) Spindle Speed
  • IPM (in/min) : (Inches Per Minute) Also called Feed Rate. Rate at which the work
    • piece is moved into the tool.
  • MRR (in3/min) : (Metal Removal Rate) Rate of volume removal
  • HP : (Horse Power) necessary power

Formulas
  • RPM = SFM*12/(1.618*D)
  • IPM = FPT*N*RPM
  • MRR = IPM*DOC*D
  • HP = MMR*HPF

Input Air Turbine Spindles™ governed speeds from 25,000 to 90,000RPM and you will see the scale of savings these direct drive spindles can achieve in your application.