When installing a parallel key, the following operating points and precautions will help ensure that the parallelism of the key meets the design requirements:
Preparation Before Installation
Part Inspection:
Carefully inspect the keyways of the shaft and hub to ensure there are no burrs, impurities, oil stains, etc., and that the surfaces are flat and smooth. Defects in the keyway can affect installation accuracy and fitting clearance, leading to non-compliance with parallelism requirements.
Verify that the key's dimensions (length, width, height, etc.) match the design specifications to prevent parallelism issues due to size errors.
Cleaning:
Use clean wiping cloths, brushes, or other tools to thoroughly clean the shaft, hub keyway, and key. For severe oil stains, employ specialized cleaning agents, followed by drying with clean compressed air. This ensures a clean, dry surface, providing a solid foundation for key installation.
Operation Points During Installation
Correct Installation Direction:
Clarify the key's installation direction to ensure the working surfaces (e.g., the sides of a flat key) fit tightly against the working surfaces of the shaft and hub keyways. Typically, the marked surface or the higher-precision surface of the key should face the critical mating surface to ensure uniform stress distribution and stable torque transmission.
Control Installation Force:
Avoid excessive impact force when installing the key. Use tools like copper rods or soft plastic hammers to gently tap the key into the keyway, preventing deformation of the key, shaft, or hub. If the keyway is too tight, trim it slightly, but ensure the trimming remains within tolerance limits.
Ensure Matching Clearance:
Strictly control the clearance between the key and keyway. Excessive or insufficient clearance can affect parallelism and transmission performance. For transition or interference fits, use appropriate assembly methods (e.g., heating the hub or cooling the shaft) to achieve smooth installation and specified matching accuracy.
Inspection and Adjustment After Installation
Parallelism Detection:
Use professional measuring tools (e.g., dial indicators, micrometers) to check the key's parallelism. Fix the dial indicator on a stable platform, with the probe touching the key's surface. Rotate the shaft slowly and observe the dial indicator readings to determine compliance with design requirements.
Adjustment and Correction:
If parallelism deviations are detected, adjust or correct them accordingly. Minor deviations can be resolved by fine-tuning the key's position; larger deviations may require disassembly, re-inspection of keyway and key dimensions, and repair or replacement of parts as needed until parallelism meets specifications.
