Ringfeder RfN 7012 Locking Assembly

Name: Ringfeder RfN 7012 Locking Assembly – Datasheet & Quote
Brand: Ringfeder
SKU: RfN 7012

A slim keyless locking assembly for the largest shaft diameters

The RfN 7012 is the slimmest series in the RINGFEDER locking assembly programme. It clamps a hub to a plain shaft with no key, no keyway and no shrink fit: tightening the screws drives the tapered thrust rings against the inner ring, which closes onto the shaft while the outer ring presses against the hub bore. RINGFEDER recommends the series where space is tight and forces are large, and its tech paper table runs from 19 mm to 1000 mm shaft diameter, the widest size range of any locking assembly series in the product paper.

Shaft and hub carry no keyway, so there is no notch effect and the shaft keeps its fatigue strength under reversing torque. The assembly compensates small tolerance deviations and slight mounting errors, and because nothing moves between shaft and hub, RINGFEDER states it can be clamped and released repeatedly without wear.

Technical specifications

Parameter	Specification
Manufacturer	RINGFEDER POWER TRANSMISSION GmbH, Groß-Umstadt, Germany
Series	RINGFEDER RfN 7012 locking assembly, keyless shaft-hub clamping
Shaft diameter d	19 to 1000 mm
Hub bore diameter D	47 to 1110 mm
Overall length L	27.5 to 130 mm
Transmissible torque T	306 Nm (19 x 47) to 2,352,018 Nm (1000 x 1110)
Transmissible axial force Fax	32 kN to 4,704 kN
Maximum transmissible torque Tmax	356 Nm to 3,499,454 Nm
Surface pressure on shaft pW / hub pN	130 to 266 N/mm2 / 100 to 160 N/mm2
Locking screws	M6 x 18 to M24 x 90; 8 to 82 screws depending on size
Screw tightening torque TA	17 Nm to 1,200 Nm
Weight	0.23 kg to 146 kg
Surface finish	Shaft and hub bore Ra 3.2 um or better
Tolerances	Shaft k9 to h9, hub N9 to H9; maximum permissible shaft k11 to h11, hub N11 to H11
Ordering example	RfN 7012 200 260 (d = 200 mm, D = 260 mm)

Selected sizes from the tech paper

The full table lists 75 sizes. These rows show how capacity grows with shaft diameter; the values apply to the delivery condition (slightly oiled) at the listed tightening torque TA.

d x D (mm)	L (mm)	T (Nm)	Fax (kN)	Screws	TA (Nm)	Weight (kg)
19 x 47	27,5	306	32	8 x M6 x 18	17	0.24
50 x 80	33,5	2,082	83	12 x M8 x 22	41	0.6
100 x 145	47	11,126	223	14 x M12 x 30	145	2.01
200 x 260	68	62,452	625	30 x M14 x 45	230	8.65
400 x 495	116	371,687	1,858	36 x M22 x 80	930	46
600 x 710	130	888,410	2,961	50 x M24 x 90	1200	91
1000 x 1110	130	2,352,018	4,704	82 x M24 x 90	1200	146

Sizing the hub and installing the assembly

The tech paper gives the minimum hub outside diameter DN for three hub yield strengths (Rp0.2 of 200, 300 and 400 N/mm2). For the 200 x 260 size, DN must be at least 406, 347 or 322 mm respectively, and the maximum transmissible torque Tmax is 84,027 Nm against 62,452 Nm at the rated tightening torque. RINGFEDER works these values out with factor C3 = 0.6, which assumes an unweakened hub section and a hub length of at least twice the ring width L3. If the shaft is smaller than nominal, the bore should be larger than nominal by the same amount so the assembly sits symmetrically.

Several assemblies can be fitted in series; their values can be added if they sit within four ring widths of each other. The front thrust rings carry auxiliary threads to ease removal. Reducing the screw tightening torque is possible, but the tech paper asks you to consult RINGFEDER specialists first. The product paper also lists a non self-centring sibling, RfN 7012.2, with the same dimensions, and a stainless steel RfN 7012 for washdown duty.

Confirm before ordering: shaft and hub materials, hub outside diameter, any bending load, and the torque including shock factors.

Documents and quotation

The attached PDF is the RINGFEDER tech paper for the RfN 7012 (edition 05.2024) with the complete size table. Shaft-hub connections are normally specified alongside couplings and gear units; see Electric Motors and Gear Units or the KTR ROTEX jaw coupling. Send shaft and hub diameters, torque and speed and we will check the size against the tech paper.

Ringfeder is a German manufacturer of shaft-hub connections and couplings for mechanical power transmission, with locking assemblies, shrink discs and locking elements as core product groups. These keyless connections clamp hubs to shafts by friction, so no keyway weakens the shaft and there is no backlash.

Keyless shaft-hub connections

Ringfeder publishes numbered RfN series with tech papers, for example locking assemblies in the RfN 70xx family, shrink discs in the RfN 40xx family and locking elements such as the RfN 8006. Each tech paper lists sizes, transmissible torque and axial force, screws and tolerances.

Typical uses

Ringfeder connections are used where gear wheels, sprockets, pulleys, couplings and brake discs have to be fixed on a shaft: industrial drives, conveyors, wind and mining equipment, and general machine building.

Ordering through Seven Star LLC

Seven Star LLC lists Ringfeder series from the official tech papers and quotes by shaft diameter, hub dimensions and torque. Browse the products below for specifications.

Frequently Asked Questions