NTN HF2520 Hülsenfreiläufe (25x32x20)

As a drawn-cup roller clutch, this component transmits torque in one direction and overruns in the other. The principal dimensions are 25x32x20 mm at a weight of 0.035 kg; the further technical details are listed in the specification table. Spring-loaded clamping rollers on the ramps of a thin-walled drawn steel cup form the operating principle of this design, which works as a backstop, overrunning or indexing clutch.

In the drawn cup roller clutch, spring-loaded clamping rollers sit on the ramps of a thin-walled drawn steel cup: when the shaft turns in the locking direction the rollers wedge between the ramp and the shaft surface and transmit the torque, and in the opposite direction they move back into the deep section of the ramp and release the shaft.

Backstop, overrunning clutch and indexing clutch therefore differ not in component geometry but in mounting orientation and torque path — the direction of rotation is fixed at installation, and mounting the unit the wrong way round reverses the function. The cup is pressed into the housing bore and supported by its wall, while the shaft forms the inner clamping raceway directly; hardness, surface finish and diameter tolerance of the shaft consequently enter the transmissible torque and must be treated as a design property of the clutch itself.

Versions without integrated bearing support carry no radial force and require a separate bearing position, whereas versions with additional needle roller bearing support combine shaft guidance and freewheel function in one component. Because the open type brings no sealing element with it, the choice of lubricant, the initial fill and the shielding against dirt and water rest with the installation environment, and they weigh more heavily here than on a plain rolling bearing: contamination in the clamping contact acts directly on the switching behaviour.