Ringfeder RfN 4073 Mini Shrink Disc, 14-160 mm

The smallest, lightest shrink disc for seals and small gears

The RfN 4073 is the mini series of the RINGFEDER shrink disc range. It has a very compact design with a low moment of inertia and, in the words of the product paper, is ideally suited to mechanical seal and small gearbox applications. Its particularly light structure makes it a fit for drives with reduced requirements for transmitted values, or with very low to no dynamic loads. Inner diameters run from 14 mm to 160 mm, and the product paper gives torques from 9 Nm to 7,260 Nm.

The working principle is the same as in the larger discs. Tightening the screws draws the thrust ring into a slit inner ring, which clamps the shaft and presses the hub, giving a friction fit with no key. The slit inner ring keeps forces and pressures on hub and shaft low. The preload can be targeted to the needs of the application by choosing the screw tightening torque.

Technical specifications

Selected sizes from the tech paper

Each size is tabulated for three shaft diameters; the 46 x 80 disc lists 400, 470 and 550 Nm for shafts of 38, 40 and 42 mm. Values are transmissible torque T at the stated tightening torque TA, with Tmax tabulated separately (for example 26 Nm for the 14 x 34 and 589 Nm for the 46 x 80).

Design notes and benefits

The mini series shares the family benefits: no keyway, step or spline is cut into the shaft, so hubs can sit at any point or angle; the disc releases itself when the screws are loosened; and plain shaft and bore diameters are enough. The paper rates the joint for static, dynamic and impact loads and invites customers to discuss compensation of small tolerance errors with its engineers.

The mini series is sized for low to moderate values, and the paper cautions that its function values assume lubricated screws and cones, oiled shaft surfaces and the full permitted clearance. Maximum clearance S between shaft and bore grows with diameter: 0.011 mm for 6 to 10 mm shafts, 0.017 mm for 18 to 30 mm, 0.048 mm for 50 to 80 mm and 0.079 mm for 120 to 180 mm. Shafts need Ra 3.2 um, and hollow shafts need a conversation with the engineering team. A stronger neighbour such as the RfN 4061 or RfN 4161 may suit higher torque. Confirm before ordering: shaft diameter within the dw range, screw grade (M4 sizes are 8.8) and torque with shock factor.

Documents and quotation

The attached PDF is the RINGFEDER RfN 4073 tech paper (10.2024). Related locking devices are listed under Couplings & Shaft Locking Devices. Send shaft diameter, hub dimensions and torque for a size check.