1. Basic concepts
DD (Double D type): refers to the connection method where the shaft end is two parallel planes, fixed by bolts, anti slip and high torque.

Single U-shaped joint (cross shaft universal joint): composed of a cross shaft and two U-shaped forks, allowing power transmission at a certain angle between the two shafts.

2. Specification parameters
Size: 3/4 inch (approximately 19mm) shaft diameter, need to confirm thread or aperture matching.

Material: Usually alloy steel (such as 20CrMnTi) or stainless steel, the surface may undergo hardening treatment.

Maximum angle: generally 15 ° -30 °, the larger the angle, the lower the efficiency.

Speed/torque: Please refer to the manufacturer's data to avoid overloading.

3. Application scenarios
Industrial machinery: equipment such as conveyors, pumps, and agricultural machinery that require steering transmission.

Automobiles/ships: transmission system, steering mechanism.

Other fields: such as robot joints and special tools.

4. Selection precautions
Load requirements: Dynamic/static torque and speed must meet the requirements.

Environmental factors: Choose stainless steel or coating for humid/corrosive environments.

Installation space: Confirm that the size of the universal joint matches the equipment.

Supporting components: Check the compatibility between the shaft end (DD type) and the mating components.

5. Maintenance and troubleshooting
Lubrication: Regularly add high-temperature grease (such as NLGI # 2).

Inspection: Wear, abnormal noise, and looseness should be replaced in a timely manner.

Lifespan: Depending on the load and frequency of use, typically tens of thousands of hours.