microARC 4 4th Axis Machining


Allowing high-precision 4th axis machining in a compact footprint, the microARC 4 is designed to work with all Tormach machines—from the PCNC 440 Mill to the 1100 M/MX Mill. It reduces both operator workload and cycle times with a high-quality, low-maintenance harmonic drive which provides extremely precise motion control, coupled with much higher rapid speeds than a worm-drive unit.


Using Tormach's new hollow shaft stepper motor design, long stock can be passed all the way through the chuck, harmonic drive, and motor to enable high volume production without reduced yield from pre-cutting stock into short lengths. With flexible mounting options, it can be used on either the right or left side of the machine table.





  • Near-zero backlash levels because of the harmonic drive system; compared to a similar size worm-drive 4th axis unit, the microARC 4 achieves anywhere from a 400 to 600% reduction in backlash
  • No maintenance required, providing a much lower cost of ownership than an oil-filled worm drive unit, which requires periodic oil changes and top-ups
  • Smoother start and stop motion due to a crossed-roller bearing instead of a large oil-film hydrodynamic bearing that is common on most other 4th axis units, which require a transition from static to dynamic friction
  • 19mm center bore pass-through for long bar stock; stock can be passed all the way through the chuck and out the back of the 4th axis—no need to cut stock into small pieces when doing a production run of many parts
  • The microARC 4’s motor is mounted directly in-line with the axis of rotation instead of off to the side, providing an extremely compact footprint
  • Lightweight and strong aluminum body allows for installation into the machine without a hoist or team lift.
  • Price: $2,299

The 4th Axis Kit Includes:

  • 4th axis with NEMA 34 stepper drive and harmonic reducer
  • 100mm 3-Jaw Chuck
  • Standard and reversible jaws        
  • ER 40 Collet Face Plate
  • PCNC 440 mounting hardware
Height6.97 in (178 mm)With handle installed
5.7 in. (145 mm)Without handle
Table to Centerline3.1 in. (80 mm)Height of 4th axis centerline.
Length10.2 in. (260 mm)From rear face to tip of 3-jaw chuck.
Thru-Bore Diameter0.79 in. (20 mm)
Angular Resolution26 arc-secAngular resolution takes into account motor step size and gear reduction.
Backlash18 arc-sec
Maximum Holding Torque28 ft-lb (39 Nm)When moving, the 4th axis gearbox should never be loaded to more than 40% (17 Nm) of holding torque to avoid damage or accelerated wear.
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