Model 4R BLOCK-HEAD®

The combination of reasonable load capacities with 10,000 rpm maximum speed makes the model 4R a first choice for most high-accuracy applications. The stator’s generous mounting surfaces provide for an extremely rigid assembly, while the compact structure allows an installation where conventional spindles will never fit.

Specifications (at 150 psi)

Load Capacity Ultimate Working
Radial 100 lb 50 lb
Axial 400 lb 200 lb
Tilt 400 lb-in 200 lb-in
Stiffness Radial 0.67 lb/microinch
Axial 2.0 lb/microinch
Tilt 4.0 lb-in/microradian
Error Motion Radial < 1 microinch
Axial < 1 microinch
Tilt < 0.1 microradian
Total Weight 19 lb
Rotor Weight 7.7 lb
Rotor Inertia 0.73 oz-in-sec2
Maximum Speed 7,500 rpm
Air Consumption < 2 scfm
Metric Specifications


Load capacity and stiffness are approximately linear with air pressure.

Ultimate load capacity is measured when metal-to-metal contact is made across the bearing surfaces. Working load capacity is half of the ultimate load capacity. Rotor weight must be included as part of total spindle load.

Axial and tilt loads are supported by the same bearing surfaces. Consequently, a load applied in one mode reduces the other mode proportionally.

High speed or high inertia applications require rotor containment. Maximum speed is dependent on application. Consult Professional Instruments for further information with regard to speed.