1/4"-80 Screw with Differential Adjuster


Differential Adjuster Screw

  • 25 µm/rev Fine Adjustment
  • Fine Adjustment Range: 0.06" (1.5 mm)
  • Coarse Adjustment Thread: 1/4"-80


  • Length of Screw: 1" (25 mm)
  • Coarse Thread: 1/4"-80
  • Fine Adjustment Range: 400 ± 20 µm
  • Fine Adjustment Resolution: 25 µm/rev
  • On-Axis Load Capacity: 11.25 lbs (5.1 kg)
  • Recommended Preload: 1 to 2 lbs (0.5 to 1 kg)

The DAS110 is ideal as a drop-in replacement for the standard 1/4"-80 adjusters used on most Thorlabs' Kinematic Mirror Mounts.

Coarse Adjustment
The knob A is fastened to the 1/4"-80 externally threaded Main Body B, as shown in the drawing above. This mechanism provides the coarse angular adjustment of the kinematic mount. Alternatively, knob "A" may be removed to expose a 5/64" hex socket which may also be used for coarse angular adjustment.

Fine Adjustment
The fine-adjustment (25 µm/rev) is actuated by inserting a 1/16" hex wrench through the clearance hole in the adjuster knob, or into the smaller hex socket if knob A is removed. For details on this hex mechanism, click on the mechanical drawing above for a detailed view. Each rotation of the DAS110 fine-adjustment mechanism yields a highly de-magnified displacement of just 25 µm.

The Main Body B is also internally threaded with an M3 x 0.40 thread, this thread holds the intermediate actuator C, which may be rotated by a hex wrench. The key to the design is that the intermediate actuator is both internally and externally threaded allowing a differential movement to be achieved between the intermediate actuator C and the Push Rod D, as shown in the drawing above.

The external thread of the intermediate actuator is the same M3 x 0.40 mm thread internal to the Main Body. When the intermediate actuator is rotated clockwise, it moves out of the Main body by 400 µm per revolution. Connected to the internal thread of the intermediate actuator is the Push Rod; the Push Rod mates to the intermediate actuator via a M3 x 0.375 thread and is restricted from rotating by the main body. Now as intermediate actuatoris rotated, it advances at the rate of 400 µm/rev. but the Push Rod retreats at 375 µm/rev. This results in a differential motion of the Push Rod that is equal to the net difference of the pitch of the two threads for total displacement of 25 µm/rev.


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