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Friction joint

A friction joint is a component inserted between a shaft and a boss (hub). Tightening the clamping bolts pushes the inner and outer rings radially outward by wedge action, and the resulting friction force secures the shaft and boss together. Torque and axial load (thrust force) can be transmitted without keys or keyways, and the fastening position can be set freely in both the axial and rotational directions, which simplifies positioning. Loosening the bolts releases the joint, and the removal screw holes allow disassembly, reducing assembly, adjustment, and maintenance effort. Used in power transmission sections that fix pulleys, sprockets, gears, couplings, and similar parts to a shaft, it is available in standard models and in specifications with anti-rust treatment.

How to choose Friction joint

  1. 1. Match the Shaft Diameter and Boss Bore Diameter

    The applicable shaft diameter d is the outer diameter of the shaft to be installed, and the outer diameter D is the dimension that fits into the boss bore. Friction fastening depends on controlling the fit clearance, so also confirm that the shaft and boss bore can be machined to the manufacturer's specified tolerances and surface roughness.

  2. 2. Allow a Margin in Allowable Transmission Torque

    If the allowable transmission torque T is exceeded, the fastening surfaces slip, causing misalignment and wear. Select based not only on the motor's rated torque but also on the peak torque during startup or impact loads multiplied by a service factor.

  3. 3. Check Simultaneous Action with Thrust Force

    For applications with axial loads, check the allowable thrust force. When torque and thrust force act simultaneously, they share the friction force, so each allowable value may not be usable independently; confirm the manufacturer's handling of combined loads.

  4. 4. Examine Boss Strength from Side Pressure on the Boss

    During fastening, surface pressure acts on the inner surface of the boss, which pushes it outward. Calculate the required boss outer diameter and wall thickness from the boss side pressure and the yield point of the boss material, and for thin-walled bosses or low-strength materials such as aluminum, check for breakage or deformation. Examine the shaft side in the same way using the shaft side pressure.

  5. 5. Review the Relationship Between Overall Length and Boss Width

    The overall length L is the axial fastening length. If the boss width is shorter than this, the fastening surface is insufficient and the performance will not be achieved. Together with the installation space, confirm that the boss width satisfies the overall length and that working space for bolt heads and tools is secured.

  6. 6. Tighten Evenly to the Specified Tightening Torque

    Because transmission performance depends on the clamping force of the clamping bolts, control the tightening torque (1 to 142 N·m for the listed products) with a torque wrench, and tighten evenly in several passes following a diagonal sequence. Also confirm in advance the required tool size and how to use the removal screw holes.

This guide was written by AI based on the listed products' documents and specification items. Check each manufacturer's documents before adopting.