4R Twin-Mount

The model 4R Twin-Mount spindle combines a high-power brushless-DC motor (liquid cooled) with a model 4R BLOCK-HEAD® air bearing spindle for the most demanding applications. This is the spindle to use in a rapid-cycle, start/stop operation, or when the ultimate in speed stability is required.


  • Model 4R BLOCK-HEAD® air bearing spindle
  • Cast-iron housing for horizontal axis or vertical axis operation
  • Custom faceplate per customer specifications*
  • Dynamically-balanced spindle rotor
  • Brushless-DC motor mounted directly to the spindle
  • Resolver motor commutation for smooth rotation
  • Motor controller with wide speed range
  • Available with integral 1 hp AC induction motor
  • All required connectors and cables


Speed Ranges: 0-2,000 rpm
0-5,000 rpm
0-7,500 rpm

Torque: Up to 60 lb-in continuous

Speed Regulation: As low as 0.0001%

Motor performance can be tailored to your application. Motors with narrower speed ranges will have better low-speed torque and speed regulation. Load capacity, stiffness, and accuracy of the 4R BLOCK-HEAD® air bearing spindle are unaffected by the motorization process.


  • Motor style
  • Encoders of various levels of precision
  • Vacuum work holding
  • Water cooling for motor
  • Piloted faceplate for ultra-accurate interchangeable chucks, collets, or wheel mounts


  • Ultra-precise workheads for I.D. and O.D. grinding
  • Ultra-precise lathe headstocks
  • Spin table for Moore G-18 jig grinder
  • Spin table for roto grinding on a surface
  • Flycutter spindle for ultra-flat mirrors
  • Grinder wheelheads, especially for diamond wheels
  • Roundness testers

See Price List