Machine Tool Spindle Specification

Spindles used in machine tools are rotating components used to hold and drive cutting tools or workpieces on milling machines, lathes and other machine tools. For all spindles used in machine tools, the specifications that are to be considered as follows:

Performance Specifications
The following factors are to be considered for performance specifications of spindles:

• Operating Speed: This is the rotational speed up to maximum under load.
  
  
• Spindle Power: This is the maximum rotational power that a spindle can operate and provide operate within specifications.
  
  
• Maximum Torque: This is the maximum continuous torque transmission, excluding peak ratings.
  
  
• Input Voltage (if required)

Spindle Drive
Spindles are activated by the following:

• Gear Drive: Driven by gears allowing high or low-speed spindle rotation.
  
  
• Belt Drive: This type of spindle drive has has pulley for drive with the help of a belt.
  
  
• Motorized: This is driven by a motor integrally built into the spindle.
  
  
• Direct / Shaft Drive: It is driven on spindle axis and the drive end has shaft for coupling or joining to drive motor.
  
  
• Pneumatic: Driven with pressurized air.
  
  
• Hydraulic: Hydrostatic or hydraulic spindle power.

Configuration
Spindles configurations are of following types:

• Cartridge: The spindle assembly can be inserted into a stationary housing.
  
  
• Block: This is a square or rectangular or a type of box housing.
  
  
• Spindle Speeder/Head: For any purposes of milling, drilling, turning or for any machine tools, the spindle can be mounted into the head.
  
  
• Foot Mounted: In such types, the housing is bolted down with the help of flanges or feet at the bottom of the housing.
  
  
• Multiple Spindle Head: These kind of spindle heads mount directly onto a machine tool and allow for milling, drilling, tapping, etc. simultaneously with multiple tool spindles. These help in speed machining operations and for repetitive precision work.
  
  
• Angle Head: Machine head mounted spindles have right-angle or adjustable angle tool rotation.

Spindle Application
The applications of spindles are wide and varied.

• Drilling: Used in drilling operations, with good thrust capacity and radial load rating.
  
  
• Boring: Used in boring, that is enlarging a hole of an already drilled hole or the machining of an internal diameter in the workpiece.
  
  
• Grinding: Used in grinding for precision size and surface finishing.
  
  
• Milling: Used with milling cutters, including a variety of machining operations and tools.
  
  
• Turning: Used in vertical or horizontal lathes and turning centers.
  
  
• Hobbing: Used to cut gear tooth profiles.
  
  
• Test Systems: Spindles contain design features which are just ideal for test setups and systems, like computer drive testing, semiconductor testing, bearing spinning and friction tests, dynamic balancing, etc.
  
  
• Tapping: Designed specifically to be used with taps to create internal threads.
  
  
• Wheel Dressing: Spindles are used in dressing, contouring, and re-profiling abrasive grinding wheels.
  
  
• Specialty Industry: Used in specialty or non-machine tools for jewelry manufacturing, optical lens processing, and many others.

Tool Mounting

• Unit designation: Unit designation for O.D., I.D., etc. can be either English as inches or fractions of an inch or Metric as millimeters or centimeters.
  
  
• Spindle interface size: This refers to the cutting tool's diameter or the grinding wheel's bore that can be mounted to the spindle.
  
  
• Tool / Workholder Mounting: This refers to mounting interface on spindle end, including mounting options for cutting tools, workpieces, grinding wheels, etc. The various options are:
  • Arbor / Shaft: Driven end here is a straight shaft for tool or wheel mounting.
    
    
  • Standard Bore: The bore is straight or standard for tool mounting.
    
    
  • Collet: Coming in standard tooling sizes and tapers, tool mounts into a collet, which is tightened properly to secure the tool for operation.
    
    
  • Threaded Hole: The shaft consists a threaded hole for screw or stud mounting, typically used in grinding wheels.
    
    
  • External Taper: The shaft has external taper, used for mounting or grinding, polishing, or buffing wheel.
    
    
  • Internal Taper: Accept standard machine tool collets.
    
    
  • Wheel Collet: They have external tapered nose designed to accept grinding wheel mounting.
    
    
  • Flanged Bore: Here, the tool end has a bore for location, with flange mounting attribute around the bore.

Spindle Options
The various options are as follows:

• Automatic Balancing spindle: This spindle with dynamic balancing system can prevent tool or wheel unbalance without using any extensive operator interaction.
  
  
• Air Purge spindle: This has an automatic blow-off of contamination, chips, dust, etc., at or near spindle bearings.
  
  
• High Frequency Drive: This allows a spindle to operate at very high speeds.
  
  
• Coolant Feed: This allows for direct application of coolant to the grinding or cutting operation.
  
  
• Linear / Compound Motion: In addition to its rotation, spindle can also move axially. Very common in drilling and other machining operations.
  
  
• Liquid Cooled: This leads to high heat dissipation capacity and can translate into higher speed ratings.