T-DM22 - Differential Adjuster for Optic Mounts, 1/4"-80 Ext. Thread, 0.5 µm/Div.

• Fine Adjustment Range: 250 µm
• Fine Adjustment per Revolution: 25 µm
• Coarse Adjustment Range: 0.72" Long 1/4"-80 Threads
• Coarse Adjustment per Revolution: 0.012" (80 TPI)
• On-Axis Load Capacity: 11 lbs (5 kg)

The T-DM22 Differential Adjuster uses two internal leadscrews; one pushes the center spindle forward at 400 µm per revolution while the other pulls it back at 375 µm per revolution.

The resultant total forward motion of the center spindle is just 25 µm for one complete revolution of the graduated knob. Each small graduation of the fine control knob is 0.5 µm; the smallest incremental move for the T-DM22 is approximately 50 nm. When performing fine adjustment the coarse adjustment mechanism can be locked by means of a small locking collar.

Prior to installation, the adjuster should be greased slightly. To install the adjuster, screw the threads into the bushing by hand. Ensure that cross threading does not occur in order to avoid damage to the adjuster and bushing.

If the fine adjustment knob on the T-DM22 is ever removed from the actuator body, it can be reattached. 

Fine Adjustment Knob Reattachment for Differential Adjusters

• Step 1: Fully remove the detached knob.
• Step 2: Apply pressure to the tip of the actuator.
• Step 3: While maintaining pressure, screw in the knob 2 to 3 threads.
• Step 4: Once threaded, remove pressure from Step 2 and continue to slowly screw in the knob. Please note that this should be done slowly and with little force. If too much force is applied, cross-threading may occur and may damage the threads.

A differential adjuster consists of four basic parts: outer body, coarse adjustment lock, inner spindle, and fine adjustment knob. Using the T-DM22 as an example, the video to the left demonstrates how these four parts come together to create a device that allows for coarse and fine adjustments. Also detailed are two different methods of mounting these actuators into an assembly.